| Message ID | 1511816284-12145-1-git-send-email-atull@kernel.org |
|---|---|
| Headers | show |
| Series | of: Add whitelist | expand |
On 11/27/17 15:58, Alan Tull wrote: > Here's a proposal for a whitelist to lock down the dynamic device tree. > > For an overlay to be accepted, all of its targets are required to be > on a target node whitelist. > > Currently the only way I have to get on the whitelist is calling a > function to add a node. That works for fpga regions, but I think > other uses will need a way of having adding specific nodes from the > base device tree, such as by adding a property like 'allow-overlay;' > or 'allow-overlay = "okay";' If that is acceptable, I could use some > advice on where that particular code should go. > > Alan > > Alan Tull (2): > of: overlay: add whitelist > fpga: of region: add of-fpga-region to whitelist > > drivers/fpga/of-fpga-region.c | 9 ++++++ > drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ > include/linux/of.h | 12 +++++++ > 3 files changed, 94 insertions(+) > The plan was to use connectors to restrict where an overlay could be applied. I would prefer not to have multiple methods for accomplishing the same thing unless there is a compelling reason to do so. -Frnank -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@gmail.com> wrote: > On 11/27/17 15:58, Alan Tull wrote: >> Here's a proposal for a whitelist to lock down the dynamic device tree. >> >> For an overlay to be accepted, all of its targets are required to be >> on a target node whitelist. >> >> Currently the only way I have to get on the whitelist is calling a >> function to add a node. That works for fpga regions, but I think >> other uses will need a way of having adding specific nodes from the >> base device tree, such as by adding a property like 'allow-overlay;' >> or 'allow-overlay = "okay";' If that is acceptable, I could use some >> advice on where that particular code should go. >> >> Alan >> >> Alan Tull (2): >> of: overlay: add whitelist >> fpga: of region: add of-fpga-region to whitelist >> >> drivers/fpga/of-fpga-region.c | 9 ++++++ >> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >> include/linux/of.h | 12 +++++++ >> 3 files changed, 94 insertions(+) >> > > The plan was to use connectors to restrict where an overlay could be applied. > I would prefer not to have multiple methods for accomplishing the same thing > unless there is a compelling reason to do so. Connector nodes need a mechanism to enable themselves, too. I don't think connector nodes are going to solve every usecase. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Nov 29, 2017 at 7:31 AM, Rob Herring <robh+dt@kernel.org> wrote: > On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@gmail.com> wrote: >> On 11/27/17 15:58, Alan Tull wrote: >>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>> >>> For an overlay to be accepted, all of its targets are required to be >>> on a target node whitelist. >>> >>> Currently the only way I have to get on the whitelist is calling a >>> function to add a node. That works for fpga regions, but I think >>> other uses will need a way of having adding specific nodes from the >>> base device tree, such as by adding a property like 'allow-overlay;' >>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>> advice on where that particular code should go. >>> >>> Alan >>> >>> Alan Tull (2): >>> of: overlay: add whitelist >>> fpga: of region: add of-fpga-region to whitelist >>> >>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>> include/linux/of.h | 12 +++++++ >>> 3 files changed, 94 insertions(+) >>> >> >> The plan was to use connectors to restrict where an overlay could be applied. >> I would prefer not to have multiple methods for accomplishing the same thing >> unless there is a compelling reason to do so. > > Connector nodes need a mechanism to enable themselves, too. I don't > think connector nodes are going to solve every usecase. > > Rob The two methods I'm suggesting are intended to handle different cases. There will exist some drivers that by their nature will want every instance to be enabled for overlays, such as fpga regions. The other case is where drivers could support overlays but that's not the widespread use for them. So no need to enable every instance of that driver for overlays. In that case the DT property provides some granularity, only enabling overlays for specific instances of that driver, leaving the rest of the DT locked down. If we only want one method, I would choose having the DT property only and not exporting the functions. Users would have to add the property for every FPGA region but that's not really painful. This would have the benefit of still keeping the DT locked down unless someone specifically wanted to enable some regions for overlays for their particular use. Alan -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 11/29/17 04:20, Frank Rowand wrote: > On 11/27/17 15:58, Alan Tull wrote: >> Here's a proposal for a whitelist to lock down the dynamic device tree. >> >> For an overlay to be accepted, all of its targets are required to be >> on a target node whitelist. >> >> Currently the only way I have to get on the whitelist is calling a >> function to add a node. That works for fpga regions, but I think >> other uses will need a way of having adding specific nodes from the >> base device tree, such as by adding a property like 'allow-overlay;' >> or 'allow-overlay = "okay";' If that is acceptable, I could use some >> advice on where that particular code should go. >> >> Alan >> >> Alan Tull (2): >> of: overlay: add whitelist >> fpga: of region: add of-fpga-region to whitelist >> >> drivers/fpga/of-fpga-region.c | 9 ++++++ >> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >> include/linux/of.h | 12 +++++++ >> 3 files changed, 94 insertions(+) >> > > The plan was to use connectors to restrict where an overlay could be applied. > I would prefer not to have multiple methods for accomplishing the same thing > unless there is a compelling reason to do so. Going back one level in my thinking, I don't think that having a driver mark a node as a location where an overlay fragment can be applied is serving a useful purpose. Any driver, including any driver loaded as a module, could mark a node as ok. I don't see how this is providing any meaningful restriction on where an overlay fragment can be applied. -Frank -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 11/29/17 04:20, Frank Rowand wrote: > On 11/27/17 15:58, Alan Tull wrote: >> Here's a proposal for a whitelist to lock down the dynamic device tree. >> >> For an overlay to be accepted, all of its targets are required to be >> on a target node whitelist. >> >> Currently the only way I have to get on the whitelist is calling a >> function to add a node. That works for fpga regions, but I think >> other uses will need a way of having adding specific nodes from the >> base device tree, such as by adding a property like 'allow-overlay;' >> or 'allow-overlay = "okay";' If that is acceptable, I could use some >> advice on where that particular code should go. >> >> Alan >> >> Alan Tull (2): >> of: overlay: add whitelist >> fpga: of region: add of-fpga-region to whitelist >> >> drivers/fpga/of-fpga-region.c | 9 ++++++ >> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >> include/linux/of.h | 12 +++++++ >> 3 files changed, 94 insertions(+) >> > > The plan was to use connectors to restrict where an overlay could be applied. > I would prefer not to have multiple methods for accomplishing the same thing > unless there is a compelling reason to do so. Going back one level in my thinking, I don't think that having a driver mark a node as a location where an overlay fragment can be applied is serving a useful purpose. Any driver, including any driver loaded as a module, could mark a node as ok. I don't see how this is providing any meaningful restriction on where an overlay fragment can be applied. -Frank -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 11/29/17 08:31, Rob Herring wrote: > On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@gmail.com> wrote: >> On 11/27/17 15:58, Alan Tull wrote: >>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>> >>> For an overlay to be accepted, all of its targets are required to be >>> on a target node whitelist. >>> >>> Currently the only way I have to get on the whitelist is calling a >>> function to add a node. That works for fpga regions, but I think >>> other uses will need a way of having adding specific nodes from the >>> base device tree, such as by adding a property like 'allow-overlay;' >>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>> advice on where that particular code should go. >>> >>> Alan >>> >>> Alan Tull (2): >>> of: overlay: add whitelist >>> fpga: of region: add of-fpga-region to whitelist >>> >>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>> include/linux/of.h | 12 +++++++ >>> 3 files changed, 94 insertions(+) >>> >> >> The plan was to use connectors to restrict where an overlay could be applied. >> I would prefer not to have multiple methods for accomplishing the same thing >> unless there is a compelling reason to do so. > > Connector nodes need a mechanism to enable themselves, too. I don't > think connector nodes are going to solve every usecase. > > Rob > The overlay code related to connectors does not exist yet, so my comment is going to be theoretical. I would expect the overlay code to check that the target of the overlay fragment is a connector node, so there is no need to explicitly "enable" applying an overlay to a connector node. -Frank -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 11/29/17 11:11, Alan Tull wrote: > On Wed, Nov 29, 2017 at 7:31 AM, Rob Herring <robh+dt@kernel.org> wrote: >> On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@gmail.com> wrote: >>> On 11/27/17 15:58, Alan Tull wrote: >>>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>>> >>>> For an overlay to be accepted, all of its targets are required to be >>>> on a target node whitelist. >>>> >>>> Currently the only way I have to get on the whitelist is calling a >>>> function to add a node. That works for fpga regions, but I think >>>> other uses will need a way of having adding specific nodes from the >>>> base device tree, such as by adding a property like 'allow-overlay;' >>>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>>> advice on where that particular code should go. >>>> >>>> Alan >>>> >>>> Alan Tull (2): >>>> of: overlay: add whitelist >>>> fpga: of region: add of-fpga-region to whitelist >>>> >>>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>>> include/linux/of.h | 12 +++++++ >>>> 3 files changed, 94 insertions(+) >>>> >>> >>> The plan was to use connectors to restrict where an overlay could be applied. >>> I would prefer not to have multiple methods for accomplishing the same thing >>> unless there is a compelling reason to do so. >> >> Connector nodes need a mechanism to enable themselves, too. I don't >> think connector nodes are going to solve every usecase. >> >> Rob > > The two methods I'm suggesting are intended to handle different cases. > There will exist some drivers that by their nature will want every > instance to be enabled for overlays, such as fpga regions. The other > case is where drivers could support overlays but that's not the > widespread use for them. So no need to enable every instance of that > driver for overlays. I understand what the paragraph, to this point, means. But I had to read it several times to understand it because the way the concept is phrased clashed with my mental model. The device node is not an instance of a driver, which is why I was getting confused. (Yes, I do understand that the paragraph is talking about multiple device nodes that are bound to the same driver, but my mental model is tied to the device node, not to the driver.) If each of the device nodes in question is a connector, then each of the nodes will bind to a connector driver, based on the value of the compatible property. (This is of course a theoretical assumption on my part since the connectors are not yet implemented.) If the connector node is an fpga, or an fpga region (I may be getting my terminology wrong here - please correct as needed) then an fpga overlay could be applied to the node. If I understand what you are saying, there will be some fpga connector nodes for which the usage at a given moment might be programmed to function in a manner that will not be described by an overlay, but at a different moment in time may be programmed in a way that needs to be described by an overlay. So there may be some times that it is valid to apply an overlay to the connector node and times that it is not valid to apply an overlay to the connector node. Is my understanding correct, or am I still confused? -Frank > In that case the DT property provides some > granularity, only enabling overlays for specific instances of that > driver, leaving the rest of the DT locked down.> > If we only want one method, I would choose having the DT property only > and not exporting the functions. Users would have to add the property > for every FPGA region but that's not really painful. This would have > the benefit of still keeping the DT locked down unless someone > specifically wanted to enable some regions for overlays for their > particular use. > > Alan > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Nov 29, 2017 at 4:47 PM, Frank Rowand <frowand.list@gmail.com> wrote: > On 11/29/17 04:20, Frank Rowand wrote: >> On 11/27/17 15:58, Alan Tull wrote: >>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>> >>> For an overlay to be accepted, all of its targets are required to be >>> on a target node whitelist. >>> >>> Currently the only way I have to get on the whitelist is calling a >>> function to add a node. That works for fpga regions, but I think >>> other uses will need a way of having adding specific nodes from the >>> base device tree, such as by adding a property like 'allow-overlay;' >>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>> advice on where that particular code should go. >>> >>> Alan >>> >>> Alan Tull (2): >>> of: overlay: add whitelist >>> fpga: of region: add of-fpga-region to whitelist >>> >>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>> include/linux/of.h | 12 +++++++ >>> 3 files changed, 94 insertions(+) >>> >> >> The plan was to use connectors to restrict where an overlay could be applied. >> I would prefer not to have multiple methods for accomplishing the same thing >> unless there is a compelling reason to do so. > > Going back one level in my thinking, I don't think that having a driver mark > a node as a location where an overlay fragment can be applied is serving a > useful purpose. Any driver, including any driver loaded as a module, > could mark a node as ok. I don't see how this is providing any meaningful > restriction on where an overlay fragment can be applied. It serves to separate the setting of which nodes overlays can be applied to and the mechanism to apply them (checking permissions). The former can't be centralized and the latter can be. For example, something in the kernel enables overlays on a node or nodes, then the overlay is applied with configfs interface and no board specific code involved. My concern is not whether any kernel component can enable applying of overlays, but userspace. If it is a kernel component, then it is explicit. And an OOT kernel module doesn't count because there's no ABI guarantee there. I agree that this patch series alone is not all that useful with only in kernel users. It is only really interesting when we have a userspace interface. However, an implementation with a flag bit is so little code, I'm fine taking it now and not having to update all in kernel users when adding a userspace interface. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Nov 30, 2017 at 6:46 AM, Frank Rowand <frowand.list@gmail.com> wrote: > On 11/29/17 11:11, Alan Tull wrote: >> On Wed, Nov 29, 2017 at 7:31 AM, Rob Herring <robh+dt@kernel.org> wrote: >>> On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@gmail.com> wrote: >>>> On 11/27/17 15:58, Alan Tull wrote: >>>>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>>>> >>>>> For an overlay to be accepted, all of its targets are required to be >>>>> on a target node whitelist. >>>>> >>>>> Currently the only way I have to get on the whitelist is calling a >>>>> function to add a node. That works for fpga regions, but I think >>>>> other uses will need a way of having adding specific nodes from the >>>>> base device tree, such as by adding a property like 'allow-overlay;' >>>>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>>>> advice on where that particular code should go. >>>>> >>>>> Alan >>>>> >>>>> Alan Tull (2): >>>>> of: overlay: add whitelist >>>>> fpga: of region: add of-fpga-region to whitelist >>>>> >>>>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>>>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>>>> include/linux/of.h | 12 +++++++ >>>>> 3 files changed, 94 insertions(+) >>>>> >>>> >>>> The plan was to use connectors to restrict where an overlay could be applied. >>>> I would prefer not to have multiple methods for accomplishing the same thing >>>> unless there is a compelling reason to do so. >>> >>> Connector nodes need a mechanism to enable themselves, too. I don't >>> think connector nodes are going to solve every usecase. >>> >>> Rob >> >> The two methods I'm suggesting are intended to handle different cases. >> There will exist some drivers that by their nature will want every >> instance to be enabled for overlays, such as fpga regions. The other >> case is where drivers could support overlays but that's not the >> widespread use for them. So no need to enable every instance of that >> driver for overlays. > > I understand what the paragraph, to this point, means. But I had to > read it several times to understand it because the way the concept is > phrased clashed with my mental model. Hi Frank, I see where my explanation is confusing things. I was talking about two methods for marking a node as being a valid target for an overlay (use a function or add a DT property). I'll drop the idea of using a DT property to enable a node for overlays and only focus on my proposal of a function to enable nodes. > > The device node is not an instance of a driver, which is why I was > getting confused. (Yes, I do understand that the paragraph is talking > about multiple device nodes that are bound to the same driver, but > my mental model is tied to the device node, not to the driver.) > > If each of the device nodes in question is a connector, then each of > the nodes will bind to a connector driver, based on the value of the > compatible property. (This is of course a theoretical assumption on > my part since the connectors are not yet implemented.) > > If the connector node is an fpga, or an fpga region (I may be getting > my terminology wrong here - please correct as needed) then an fpga > overlay could be applied to the node. We're still pre-connector currently, but yes I want to mark FPGA regions as being valid targets. Then I can use Pantelis' configfs interface to apply overlays while leaving the rest of the DT locked down. That's the FPGA use of this patch in the pre-connector era of things. > > If I understand what you are saying, there will be some fpga connector > nodes for which the usage at a given moment might be programmed to > function in a manner that will not be described by an overlay, but > at a different moment in time may be programmed in a way that needs > to be described by an overlay. So there may be some times that it > is valid to apply an overlay to the connector node and times that > it is not valid to apply an overlay to the connector node. I think connectors would likely always be valid targets (but I could be wrong) and other nodes would not be valid targets. The DT needs a way to mark some nodes as valid targets, currently it doesn't have a way of doing that. Every connector driver's probe could use this code to mark itself as a valid target. > > Is my understanding correct, or am I still confused? Hope that helps, sorry for the muddled explanation earlier. Alan > > -Frank > >> In that case the DT property provides some >> granularity, only enabling overlays for specific instances of that >> driver, leaving the rest of the DT locked down.> >> If we only want one method, I would choose having the DT property only >> and not exporting the functions. Users would have to add the property >> for every FPGA region but that's not really painful. This would have >> the benefit of still keeping the DT locked down unless someone >> specifically wanted to enable some regions for overlays for their >> particular use. >> >> Alan >> > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Nov 30, 2017 at 6:18 AM, Frank Rowand <frowand.list@gmail.com> wrote: > On 11/29/17 08:31, Rob Herring wrote: >> On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@gmail.com> wrote: >>> On 11/27/17 15:58, Alan Tull wrote: >>>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>>> >>>> For an overlay to be accepted, all of its targets are required to be >>>> on a target node whitelist. >>>> >>>> Currently the only way I have to get on the whitelist is calling a >>>> function to add a node. That works for fpga regions, but I think >>>> other uses will need a way of having adding specific nodes from the >>>> base device tree, such as by adding a property like 'allow-overlay;' >>>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>>> advice on where that particular code should go. >>>> >>>> Alan >>>> >>>> Alan Tull (2): >>>> of: overlay: add whitelist >>>> fpga: of region: add of-fpga-region to whitelist >>>> >>>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>>> include/linux/of.h | 12 +++++++ >>>> 3 files changed, 94 insertions(+) >>>> >>> >>> The plan was to use connectors to restrict where an overlay could be applied. >>> I would prefer not to have multiple methods for accomplishing the same thing >>> unless there is a compelling reason to do so. >> >> Connector nodes need a mechanism to enable themselves, too. I don't >> think connector nodes are going to solve every usecase. >> >> Rob >> > > The overlay code related to connectors does not exist yet, so my comment > is going to be theoretical. > > I would expect the overlay code to check that the target of the overlay > fragment is a connector node, so there is no need to explicitly "enable" > applying an overlay to a connector node. This will depend on how connectors are implemented. My proposal in v1 is that device nodes can have a flag bit. If its not set, then an overlay that contains fragments that target that node can't be applied. There's probably other ways a connector node could be marked as different from other nodes, but a flag bit seems simple. The advantage to this scheme is that it gives me something I can use while connectors don't exist yet and it will still will be useful later for the implementation of connectors (giving connector drivers a way of marking their device nodes as valid targets). > > -Frank -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 11/30/17 09:39, Rob Herring wrote: > On Wed, Nov 29, 2017 at 4:47 PM, Frank Rowand <frowand.list@gmail.com> wrote: >> On 11/29/17 04:20, Frank Rowand wrote: >>> On 11/27/17 15:58, Alan Tull wrote: >>>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>>> >>>> For an overlay to be accepted, all of its targets are required to be >>>> on a target node whitelist. >>>> >>>> Currently the only way I have to get on the whitelist is calling a >>>> function to add a node. That works for fpga regions, but I think >>>> other uses will need a way of having adding specific nodes from the >>>> base device tree, such as by adding a property like 'allow-overlay;' >>>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>>> advice on where that particular code should go. >>>> >>>> Alan >>>> >>>> Alan Tull (2): >>>> of: overlay: add whitelist >>>> fpga: of region: add of-fpga-region to whitelist >>>> >>>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>>> include/linux/of.h | 12 +++++++ >>>> 3 files changed, 94 insertions(+) >>>> >>> >>> The plan was to use connectors to restrict where an overlay could be applied. >>> I would prefer not to have multiple methods for accomplishing the same thing >>> unless there is a compelling reason to do so. >> >> Going back one level in my thinking, I don't think that having a driver mark >> a node as a location where an overlay fragment can be applied is serving a >> useful purpose. Any driver, including any driver loaded as a module, >> could mark a node as ok. I don't see how this is providing any meaningful >> restriction on where an overlay fragment can be applied. > > It serves to separate the setting of which nodes overlays can be > applied to and the mechanism to apply them (checking permissions). The > former can't be centralized My expectation is that determining which nodes overlays can be applied to can and _should_ be centralized, at least to begin with. If we loosen the restrictions on valid overlay application nodes then we _might_ find that we have to provide additional non-centralized permission granting. I think that the core devicetree code is the place (for initial implementation) that determining which nodes an overlay can be applied to. My expectation is that it will be implicitly obvious to the core devicetree code which nodes are connector nodes. Given that there have been several different proposals for connector implementation, my expectation may be completely wrong. So I am sure I will revisit my expectations the actual implementation of connectors arrives. Since the architecture and implementation of connectors is still so uncertain, I think it is premature to accept the changes proposed in the patch set, and the next patch set that has been proposed in response to the conversation in this thread. > and the latter can be. For example, > something in the kernel enables overlays on a node or nodes, then the > overlay is applied with configfs interface and no board specific code > involved. I agree that the permission checking should not need to involve board specific code. > My concern is not whether any kernel component can enable applying of > overlays, but userspace. If it is a kernel component, then it is > explicit. And an OOT kernel module doesn't count because there's no > ABI guarantee there. > > I agree that this patch series alone is not all that useful with only > in kernel users. It is only really interesting when we have a > userspace interface. However, an implementation with a flag bit is so > little code, I'm fine taking it now and not having to update all in > kernel users when adding a userspace interface. I think the concept of an API called by a driver, instead of the devicetree core code determining which nodes an overlay can be applied to is premature, since there is no direct need for it, and given that it is little code it can easily be added when it is needed, and we better understand how it will be used. > > Rob > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 12/05/17 11:55, Alan Tull wrote: > On Thu, Nov 30, 2017 at 6:18 AM, Frank Rowand <frowand.list@gmail.com> wrote: >> On 11/29/17 08:31, Rob Herring wrote: >>> On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@gmail.com> wrote: >>>> On 11/27/17 15:58, Alan Tull wrote: >>>>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>>>> >>>>> For an overlay to be accepted, all of its targets are required to be >>>>> on a target node whitelist. >>>>> >>>>> Currently the only way I have to get on the whitelist is calling a >>>>> function to add a node. That works for fpga regions, but I think >>>>> other uses will need a way of having adding specific nodes from the >>>>> base device tree, such as by adding a property like 'allow-overlay;' >>>>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>>>> advice on where that particular code should go. >>>>> >>>>> Alan >>>>> >>>>> Alan Tull (2): >>>>> of: overlay: add whitelist >>>>> fpga: of region: add of-fpga-region to whitelist >>>>> >>>>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>>>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>>>> include/linux/of.h | 12 +++++++ >>>>> 3 files changed, 94 insertions(+) >>>>> >>>> >>>> The plan was to use connectors to restrict where an overlay could be applied. >>>> I would prefer not to have multiple methods for accomplishing the same thing >>>> unless there is a compelling reason to do so. >>> >>> Connector nodes need a mechanism to enable themselves, too. I don't >>> think connector nodes are going to solve every usecase. >>> >>> Rob >>> >> >> The overlay code related to connectors does not exist yet, so my comment >> is going to be theoretical. >> >> I would expect the overlay code to check that the target of the overlay >> fragment is a connector node, so there is no need to explicitly "enable" >> applying an overlay to a connector node. > > This will depend on how connectors are implemented. My proposal in v1 > is that device nodes can have a flag bit. If its not set, then an > overlay that contains fragments that target that node can't be > applied. There's probably other ways a connector node could be marked > as different from other nodes, but a flag bit seems simple. The > advantage to this scheme is that it gives me something I can use while > connectors don't exist yet and it will still will be useful later for > the implementation of connectors (giving connector drivers a way of > marking their device nodes as valid targets). I think it is premature to add this code to the kernel when we don't have an agreed upon architecture for what we are trying to achieve. > >> >> -Frank > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 12/05/17 11:33, Alan Tull wrote: > On Thu, Nov 30, 2017 at 6:46 AM, Frank Rowand <frowand.list@gmail.com> wrote: >> On 11/29/17 11:11, Alan Tull wrote: >>> On Wed, Nov 29, 2017 at 7:31 AM, Rob Herring <robh+dt@kernel.org> wrote: >>>> On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@gmail.com> wrote: >>>>> On 11/27/17 15:58, Alan Tull wrote: >>>>>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>>>>> >>>>>> For an overlay to be accepted, all of its targets are required to be >>>>>> on a target node whitelist. >>>>>> >>>>>> Currently the only way I have to get on the whitelist is calling a >>>>>> function to add a node. That works for fpga regions, but I think >>>>>> other uses will need a way of having adding specific nodes from the >>>>>> base device tree, such as by adding a property like 'allow-overlay;' >>>>>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>>>>> advice on where that particular code should go. >>>>>> >>>>>> Alan >>>>>> >>>>>> Alan Tull (2): >>>>>> of: overlay: add whitelist >>>>>> fpga: of region: add of-fpga-region to whitelist >>>>>> >>>>>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>>>>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>>>>> include/linux/of.h | 12 +++++++ >>>>>> 3 files changed, 94 insertions(+) >>>>>> >>>>> >>>>> The plan was to use connectors to restrict where an overlay could be applied. >>>>> I would prefer not to have multiple methods for accomplishing the same thing >>>>> unless there is a compelling reason to do so. >>>> >>>> Connector nodes need a mechanism to enable themselves, too. I don't >>>> think connector nodes are going to solve every usecase. >>>> >>>> Rob >>> >>> The two methods I'm suggesting are intended to handle different cases. >>> There will exist some drivers that by their nature will want every >>> instance to be enabled for overlays, such as fpga regions. The other >>> case is where drivers could support overlays but that's not the >>> widespread use for them. So no need to enable every instance of that >>> driver for overlays. >> >> I understand what the paragraph, to this point, means. But I had to >> read it several times to understand it because the way the concept is >> phrased clashed with my mental model. > > Hi Frank, > > I see where my explanation is confusing things. I was talking about > two methods for marking a node as being a valid target for an overlay > (use a function or add a DT property). I'll drop the idea of using a > DT property to enable a node for overlays and only focus on my > proposal of a function to enable nodes. > >> >> The device node is not an instance of a driver, which is why I was >> getting confused. (Yes, I do understand that the paragraph is talking >> about multiple device nodes that are bound to the same driver, but >> my mental model is tied to the device node, not to the driver.) >> >> If each of the device nodes in question is a connector, then each of >> the nodes will bind to a connector driver, based on the value of the >> compatible property. (This is of course a theoretical assumption on >> my part since the connectors are not yet implemented.) >> >> If the connector node is an fpga, or an fpga region (I may be getting >> my terminology wrong here - please correct as needed) then an fpga >> overlay could be applied to the node. > > We're still pre-connector currently, but yes I want to mark FPGA > regions as being valid targets. Then I can use Pantelis' configfs > interface to apply overlays while leaving the rest of the DT locked > down. That's the FPGA use of this patch in the pre-connector era of > things. > >> >> If I understand what you are saying, there will be some fpga connector >> nodes for which the usage at a given moment might be programmed to >> function in a manner that will not be described by an overlay, but >> at a different moment in time may be programmed in a way that needs >> to be described by an overlay. So there may be some times that it >> is valid to apply an overlay to the connector node and times that >> it is not valid to apply an overlay to the connector node. > > I think connectors would likely always be valid targets (but I could > be wrong) and other nodes would not be valid targets. The DT needs a > way to mark some nodes as valid targets, currently it doesn't have a > way of doing that. Every connector driver's probe could use this code > to mark itself as a valid target. > >> >> Is my understanding correct, or am I still confused? > > Hope that helps, sorry for the muddled explanation earlier. No need to be sorry, I always value what you have to say, and usually become more educated from reading what you write. We still seem to be talking at cross purposes. It seems that the model that you are describing is driver centric. My model is node centric. Once we figure out what the connector implementation and architecture are, it might be the case that each connector node has a driver bound to it, and that driver is able to tell the devicetree core code that the node that it is bound to is a valid place to apply an overlay. But I currently think that the core infrastructure code is what should recognize that a connector node is a valid place to apply an overlay. It _might_ even be the case the the connector architecture does not result in a driver being bound to the connector node. I would really prefer to get the connector architecture (and maybe also the implementation) before deciding how to handle the question of how to determine what nodes overlays can be appplied to. > > Alan > >> >> -Frank >> >>> In that case the DT property provides some >>> granularity, only enabling overlays for specific instances of that >>> driver, leaving the rest of the DT locked down.> >>> If we only want one method, I would choose having the DT property only >>> and not exporting the functions. Users would have to add the property >>> for every FPGA region but that's not really painful. This would have >>> the benefit of still keeping the DT locked down unless someone >>> specifically wanted to enable some regions for overlays for their >>> particular use. >>> >>> Alan >>> >> > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Dec 6, 2017 at 5:56 AM, Frank Rowand <frowand.list@gmail.com> wrote: > On 12/05/17 11:33, Alan Tull wrote: >> On Thu, Nov 30, 2017 at 6:46 AM, Frank Rowand <frowand.list@gmail.com> wrote: >>> On 11/29/17 11:11, Alan Tull wrote: >>>> On Wed, Nov 29, 2017 at 7:31 AM, Rob Herring <robh+dt@kernel.org> wrote: >>>>> On Wed, Nov 29, 2017 at 3:20 AM, Frank Rowand <frowand.list@gmail.com> wrote: >>>>>> On 11/27/17 15:58, Alan Tull wrote: >>>>>>> Here's a proposal for a whitelist to lock down the dynamic device tree. >>>>>>> >>>>>>> For an overlay to be accepted, all of its targets are required to be >>>>>>> on a target node whitelist. >>>>>>> >>>>>>> Currently the only way I have to get on the whitelist is calling a >>>>>>> function to add a node. That works for fpga regions, but I think >>>>>>> other uses will need a way of having adding specific nodes from the >>>>>>> base device tree, such as by adding a property like 'allow-overlay;' >>>>>>> or 'allow-overlay = "okay";' If that is acceptable, I could use some >>>>>>> advice on where that particular code should go. >>>>>>> >>>>>>> Alan >>>>>>> >>>>>>> Alan Tull (2): >>>>>>> of: overlay: add whitelist >>>>>>> fpga: of region: add of-fpga-region to whitelist >>>>>>> >>>>>>> drivers/fpga/of-fpga-region.c | 9 ++++++ >>>>>>> drivers/of/overlay.c | 73 +++++++++++++++++++++++++++++++++++++++++++ >>>>>>> include/linux/of.h | 12 +++++++ >>>>>>> 3 files changed, 94 insertions(+) >>>>>>> >>>>>> >>>>>> The plan was to use connectors to restrict where an overlay could be applied. >>>>>> I would prefer not to have multiple methods for accomplishing the same thing >>>>>> unless there is a compelling reason to do so. >>>>> >>>>> Connector nodes need a mechanism to enable themselves, too. I don't >>>>> think connector nodes are going to solve every usecase. >>>>> >>>>> Rob >>>> >>>> The two methods I'm suggesting are intended to handle different cases. >>>> There will exist some drivers that by their nature will want every >>>> instance to be enabled for overlays, such as fpga regions. The other >>>> case is where drivers could support overlays but that's not the >>>> widespread use for them. So no need to enable every instance of that >>>> driver for overlays. >>> >>> I understand what the paragraph, to this point, means. But I had to >>> read it several times to understand it because the way the concept is >>> phrased clashed with my mental model. >> >> Hi Frank, >> >> I see where my explanation is confusing things. I was talking about >> two methods for marking a node as being a valid target for an overlay >> (use a function or add a DT property). I'll drop the idea of using a >> DT property to enable a node for overlays and only focus on my >> proposal of a function to enable nodes. >> >>> >>> The device node is not an instance of a driver, which is why I was >>> getting confused. (Yes, I do understand that the paragraph is talking >>> about multiple device nodes that are bound to the same driver, but >>> my mental model is tied to the device node, not to the driver.) >>> >>> If each of the device nodes in question is a connector, then each of >>> the nodes will bind to a connector driver, based on the value of the >>> compatible property. (This is of course a theoretical assumption on >>> my part since the connectors are not yet implemented.) >>> >>> If the connector node is an fpga, or an fpga region (I may be getting >>> my terminology wrong here - please correct as needed) then an fpga >>> overlay could be applied to the node. >> >> We're still pre-connector currently, but yes I want to mark FPGA >> regions as being valid targets. Then I can use Pantelis' configfs >> interface to apply overlays while leaving the rest of the DT locked >> down. That's the FPGA use of this patch in the pre-connector era of >> things. >> >>> >>> If I understand what you are saying, there will be some fpga connector >>> nodes for which the usage at a given moment might be programmed to >>> function in a manner that will not be described by an overlay, but >>> at a different moment in time may be programmed in a way that needs >>> to be described by an overlay. So there may be some times that it >>> is valid to apply an overlay to the connector node and times that >>> it is not valid to apply an overlay to the connector node. >> >> I think connectors would likely always be valid targets (but I could >> be wrong) and other nodes would not be valid targets. The DT needs a >> way to mark some nodes as valid targets, currently it doesn't have a >> way of doing that. Every connector driver's probe could use this code >> to mark itself as a valid target. >> >>> >>> Is my understanding correct, or am I still confused? >> >> Hope that helps, sorry for the muddled explanation earlier. > > No need to be sorry, I always value what you have to say, and usually > become more educated from reading what you write. > > We still seem to be talking at cross purposes. It seems that the model > that you are describing is driver centric. My model is node centric. > > Once we figure out what the connector implementation and architecture > are, it might be the case that each connector node has a driver bound > to it, and that driver is able to tell the devicetree core code that > the node that it is bound to is a valid place to apply an overlay. > > But I currently think that the core infrastructure code is what > should recognize that a connector node is a valid place to apply > an overlay. It _might_ even be the case the the connector > architecture does not result in a driver being bound to the > connector node. > > I would really prefer to get the connector architecture (and > maybe also the implementation) before deciding how to handle > the question of how to determine what nodes overlays can be > appplied to. Hi Frank, I understand that you would want to wait until it is clear how connectors will be implemented. So this method may work for connectors or may not depending on how that all pans out. Thanks for the discussion! Alan > > >> >> Alan >> >>> >>> -Frank >>> >>>> In that case the DT property provides some >>>> granularity, only enabling overlays for specific instances of that >>>> driver, leaving the rest of the DT locked down.> >>>> If we only want one method, I would choose having the DT property only >>>> and not exporting the functions. Users would have to add the property >>>> for every FPGA region but that's not really painful. This would have >>>> the benefit of still keeping the DT locked down unless someone >>>> specifically wanted to enable some regions for overlays for their >>>> particular use. >>>> >>>> Alan >>>> >>> >> > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html