| Message ID | 20211007000954.30621-7-zev@bewilderbeest.net |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
| Series | Dynamic DT device nodes | expand |
| Context | Check | Description |
|---|---|---|
| robh/checkpatch | warning | total: 2 errors, 3 warnings, 81 lines checked |
On 10/6/21 7:09 PM, Zev Weiss wrote: > Nodes marked with this (boolean) property will have a writable status > sysfs file, which can be used to toggle them between "okay" and > "reserved", effectively hot-plugging them. Note that this will only > be effective for devices on busses that register for OF reconfig > notifications (currently spi, i2c, and platform), and only if > CONFIG_OF_DYNAMIC is enabled. > > Signed-off-by: Zev Weiss <zev@bewilderbeest.net> > --- > drivers/of/kobj.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 69 insertions(+) > > diff --git a/drivers/of/kobj.c b/drivers/of/kobj.c > index 378cb421aae1..141ae23f3130 100644 > --- a/drivers/of/kobj.c > +++ b/drivers/of/kobj.c > @@ -36,6 +36,69 @@ static ssize_t of_node_property_read(struct file *filp, struct kobject *kobj, > return memory_read_from_buffer(buf, count, &offset, pp->value, pp->length); > } > > +static ssize_t of_node_status_write(struct file *filp, struct kobject *kobj, > + struct bin_attribute *bin_attr, char *buf, > + loff_t offset, size_t count) > +{ > + int rc; > + char *newstatus; > + struct property **deadprev; > + struct property *newprop = NULL; > + struct property *oldprop = container_of(bin_attr, struct property, attr); > + struct device_node *np = container_of(kobj, struct device_node, kobj); > + > + if (WARN_ON_ONCE(strcmp(oldprop->name, "status"))) > + return -EIO; > + > + if (offset) > + return -EINVAL; > + > + if (sysfs_buf_streq(buf, count, "okay") || sysfs_buf_streq(buf, count, "ok")) > + newstatus = "okay"; > + else if (sysfs_buf_streq(buf, count, "reserved")) > + newstatus = "reserved"; > + else if (sysfs_buf_streq(buf, count, "disabled")) > + newstatus = "disabled"; > + else > + return -EINVAL; > + > + if (!strcmp(newstatus, oldprop->value)) > + return count; > + If the general approach of this patch set is the correct way to provide the desired functionality (I'm still pondering that), then a version of the following code probably belongs in drivers/of/dynamic.c so that it is easier to maintain and keep consistent with other dynamic devicetree updates. If you look at the code there that touches deadprops (eg __of_changeset_entry_apply()) you will notice that the locking issues are more extensive than what is implemented here. I'm still thinking about how this interacts with other forms of dynamic devicetree changes (eg drivers/of/dynamic.c and also overlays). > + /* > + * of_update_property_self() doesn't free replaced properties, so > + * rifle through deadprops first to see if there's an equivalent old > + * status property we can reuse instead of allocating a new one. > + */ > + mutex_lock(&of_mutex); > + for (deadprev = &np->deadprops; *deadprev; deadprev = &(*deadprev)->next) { > + struct property *deadprop = *deadprev; > + if (!strcmp(deadprop->name, "status") && > + deadprop->length == strlen(newstatus) + 1 && > + !strcmp(deadprop->value, newstatus)) { > + *deadprev = deadprop->next; > + deadprop->next = NULL; > + newprop = deadprop; > + break; > + } > + } > + mutex_unlock(&of_mutex); > + > + if (!newprop) { > + newprop = kzalloc(sizeof(*newprop), GFP_KERNEL); > + if (!newprop) > + return -ENOMEM; > + > + newprop->name = oldprop->name; > + newprop->value = newstatus; > + newprop->length = strlen(newstatus) + 1; > + } > + > + rc = of_update_property_self(np, newprop, true); -Frank > + > + return rc ? rc : count; > +} > + > /* always return newly allocated name, caller must free after use */ > static const char *safe_name(struct kobject *kobj, const char *orig_name) > { > @@ -79,6 +142,12 @@ int __of_add_property_sysfs(struct device_node *np, struct property *pp) > pp->attr.size = secure ? 0 : pp->length; > pp->attr.read = of_node_property_read; > > + if (!strcmp(pp->name, "status") && of_property_read_bool(np, "dynamic")) { > + pp->attr.attr.mode |= 0200; > + pp->attr.write = of_node_status_write; > + pp->attr.growable = true; > + } > + > rc = sysfs_create_bin_file(&np->kobj, &pp->attr); > WARN(rc, "error adding attribute %s to node %pOF\n", pp->name, np); > return rc; >
On 10/8/21 1:51 PM, Frank Rowand wrote: > On 10/6/21 7:09 PM, Zev Weiss wrote: >> Nodes marked with this (boolean) property will have a writable status >> sysfs file, which can be used to toggle them between "okay" and >> "reserved", effectively hot-plugging them. Note that this will only >> be effective for devices on busses that register for OF reconfig >> notifications (currently spi, i2c, and platform), and only if >> CONFIG_OF_DYNAMIC is enabled. >> >> Signed-off-by: Zev Weiss <zev@bewilderbeest.net> >> --- >> drivers/of/kobj.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 69 insertions(+) >> >> diff --git a/drivers/of/kobj.c b/drivers/of/kobj.c >> index 378cb421aae1..141ae23f3130 100644 >> --- a/drivers/of/kobj.c >> +++ b/drivers/of/kobj.c >> @@ -36,6 +36,69 @@ static ssize_t of_node_property_read(struct file *filp, struct kobject *kobj, >> return memory_read_from_buffer(buf, count, &offset, pp->value, pp->length); >> } >> >> +static ssize_t of_node_status_write(struct file *filp, struct kobject *kobj, >> + struct bin_attribute *bin_attr, char *buf, >> + loff_t offset, size_t count) >> +{ >> + int rc; >> + char *newstatus; >> + struct property **deadprev; >> + struct property *newprop = NULL; >> + struct property *oldprop = container_of(bin_attr, struct property, attr); >> + struct device_node *np = container_of(kobj, struct device_node, kobj); >> + >> + if (WARN_ON_ONCE(strcmp(oldprop->name, "status"))) >> + return -EIO; >> + >> + if (offset) >> + return -EINVAL; >> + >> + if (sysfs_buf_streq(buf, count, "okay") || sysfs_buf_streq(buf, count, "ok")) >> + newstatus = "okay"; >> + else if (sysfs_buf_streq(buf, count, "reserved")) >> + newstatus = "reserved"; >> + else if (sysfs_buf_streq(buf, count, "disabled")) >> + newstatus = "disabled"; >> + else >> + return -EINVAL; >> + >> + if (!strcmp(newstatus, oldprop->value)) >> + return count; >> + > > If the general approach of this patch set is the correct way to provide the desired > functionality (I'm still pondering that), then a version of the following code > probably belongs in drivers/of/dynamic.c so that it is easier to maintain and keep > consistent with other dynamic devicetree updates. If you look at the code there > that touches deadprops (eg __of_changeset_entry_apply()) you will notice that the > locking issues are more extensive than what is implemented here. > > I'm still thinking about how this interacts with other forms of dynamic devicetree > changes (eg drivers/of/dynamic.c and also overlays). > >> + /* >> + * of_update_property_self() doesn't free replaced properties, so >> + * rifle through deadprops first to see if there's an equivalent old >> + * status property we can reuse instead of allocating a new one. >> + */ >> + mutex_lock(&of_mutex); >> + for (deadprev = &np->deadprops; *deadprev; deadprev = &(*deadprev)->next) { >> + struct property *deadprop = *deadprev; >> + if (!strcmp(deadprop->name, "status") && >> + deadprop->length == strlen(newstatus) + 1 && >> + !strcmp(deadprop->value, newstatus)) { >> + *deadprev = deadprop->next; >> + deadprop->next = NULL; >> + newprop = deadprop; >> + break; >> + } >> + } >> + mutex_unlock(&of_mutex); >> + >> + if (!newprop) { >> + newprop = kzalloc(sizeof(*newprop), GFP_KERNEL); >> + if (!newprop) >> + return -ENOMEM; >> + >> + newprop->name = oldprop->name; >> + newprop->value = newstatus; >> + newprop->length = strlen(newstatus) + 1; >> + } >> + >> + rc = of_update_property_self(np, newprop, true); > > -Frank > >> + >> + return rc ? rc : count; >> +} >> + >> /* always return newly allocated name, caller must free after use */ >> static const char *safe_name(struct kobject *kobj, const char *orig_name) >> { >> @@ -79,6 +142,12 @@ int __of_add_property_sysfs(struct device_node *np, struct property *pp) >> pp->attr.size = secure ? 0 : pp->length; >> pp->attr.read = of_node_property_read; >> >> + if (!strcmp(pp->name, "status") && of_property_read_bool(np, "dynamic")) { >> + pp->attr.attr.mode |= 0200; >> + pp->attr.write = of_node_status_write; >> + pp->attr.growable = true; >> + } This isn't (yet) a request for a change to the patch, but more exposing a potential issue of interaction with overlays. The current in tree instances of updating a property value are fairly limited. Adding a userspace interface to update a property value (although limited to only a node's status value) has me thinking about the interaction with dynamic devicetree updates (of/overlay/dynamic.c) and also overlays. If a node exists in a base devicetree, containing only the property "status", then an overlay subsequently populates the node with a "dynamic" property then the sysfs status file will not be updated to be writable. If we do not allow an overlay to add a property to an existing node, then not an issue. But we have not created such overlay rules yet. Again, not a request for a change to this patch yet, just leaving a breadcrumb for myself. -Frank >> + >> rc = sysfs_create_bin_file(&np->kobj, &pp->attr); >> WARN(rc, "error adding attribute %s to node %pOF\n", pp->name, np); >> return rc; >> >
Hi Matt, Greg, On 10/8/21 1:51 PM, Frank Rowand wrote: > On 10/6/21 7:09 PM, Zev Weiss wrote: >> Nodes marked with this (boolean) property will have a writable status >> sysfs file, which can be used to toggle them between "okay" and >> "reserved", effectively hot-plugging them. Note that this will only >> be effective for devices on busses that register for OF reconfig >> notifications (currently spi, i2c, and platform), and only if >> CONFIG_OF_DYNAMIC is enabled. >> >> Signed-off-by: Zev Weiss <zev@bewilderbeest.net> >> --- >> drivers/of/kobj.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 69 insertions(+) >> >> diff --git a/drivers/of/kobj.c b/drivers/of/kobj.c >> index 378cb421aae1..141ae23f3130 100644 >> --- a/drivers/of/kobj.c >> +++ b/drivers/of/kobj.c >> @@ -36,6 +36,69 @@ static ssize_t of_node_property_read(struct file *filp, struct kobject *kobj, >> return memory_read_from_buffer(buf, count, &offset, pp->value, pp->length); >> } >> >> +static ssize_t of_node_status_write(struct file *filp, struct kobject *kobj, >> + struct bin_attribute *bin_attr, char *buf, >> + loff_t offset, size_t count) >> +{ >> + int rc; >> + char *newstatus; >> + struct property **deadprev; >> + struct property *newprop = NULL; >> + struct property *oldprop = container_of(bin_attr, struct property, attr); >> + struct device_node *np = container_of(kobj, struct device_node, kobj); >> + >> + if (WARN_ON_ONCE(strcmp(oldprop->name, "status"))) >> + return -EIO; >> + >> + if (offset) >> + return -EINVAL; >> + >> + if (sysfs_buf_streq(buf, count, "okay") || sysfs_buf_streq(buf, count, "ok")) >> + newstatus = "okay"; >> + else if (sysfs_buf_streq(buf, count, "reserved")) >> + newstatus = "reserved"; >> + else if (sysfs_buf_streq(buf, count, "disabled")) >> + newstatus = "disabled"; >> + else >> + return -EINVAL; >> + >> + if (!strcmp(newstatus, oldprop->value)) >> + return count; >> + > > If the general approach of this patch set is the correct way to provide the desired > functionality (I'm still pondering that), then a version of the following code After pondering, this approach does not appear workable to me. If we allow one property to be writable via sysfs we open the door for any property to be writable from sysfs. This will likely lead to a desire to modify more than one related property as a single transaction (so that the changes occur as a single transaction, under a single lock event, with a single notification after all of the properties are modified). This is not meant to be an exhaustive list of the issues that have already been thought through in the context of overlays (though not all of the issues have been addressed with overlays, at least many of them, such as one transaction to apply an entire overlay, have been.) I don't want to make this a long missive, but will at least note the next issue that popped up in my pondering, which is complications from modifying the same items in a devicetree via different methods, such as both writing to sysfs and applying/removing overlays. If the problems in the previous paragraph are not sufficient to prevent the sysfs approach then I can elaborate further on these additional issues. So another approach is needed. I have no yet thought this through, but I have an alternative. First, change the new property name from "dynamic" to something more descriptive like "ownership_shifts_between_os_and_others" (yes, my suggestions is way too verbose and needs to be word smithed, but the point is to clearly state the underlying action that occurs), then define the result of this variable to be driver specific, where the driver is required upon probe to instantiate the device in a manner that does not impact the other user(s) of the underlying hardware and to use a driver specific method to transfer control of the hardware between the os and the other user(s). I propose the method would be via a device specific file (or set of files) in sysfs (Greg's input invited on the use of sysfs in this manner - if I recall correctly this is the current preferred mechanism). -Frank > probably belongs in drivers/of/dynamic.c so that it is easier to maintain and keep > consistent with other dynamic devicetree updates. If you look at the code there > that touches deadprops (eg __of_changeset_entry_apply()) you will notice that the > locking issues are more extensive than what is implemented here. > > I'm still thinking about how this interacts with other forms of dynamic devicetree > changes (eg drivers/of/dynamic.c and also overlays). > >> + /* >> + * of_update_property_self() doesn't free replaced properties, so >> + * rifle through deadprops first to see if there's an equivalent old >> + * status property we can reuse instead of allocating a new one. >> + */ >> + mutex_lock(&of_mutex); >> + for (deadprev = &np->deadprops; *deadprev; deadprev = &(*deadprev)->next) { >> + struct property *deadprop = *deadprev; >> + if (!strcmp(deadprop->name, "status") && >> + deadprop->length == strlen(newstatus) + 1 && >> + !strcmp(deadprop->value, newstatus)) { >> + *deadprev = deadprop->next; >> + deadprop->next = NULL; >> + newprop = deadprop; >> + break; >> + } >> + } >> + mutex_unlock(&of_mutex); >> + >> + if (!newprop) { >> + newprop = kzalloc(sizeof(*newprop), GFP_KERNEL); >> + if (!newprop) >> + return -ENOMEM; >> + >> + newprop->name = oldprop->name; >> + newprop->value = newstatus; >> + newprop->length = strlen(newstatus) + 1; >> + } >> + >> + rc = of_update_property_self(np, newprop, true); > > -Frank > >> + >> + return rc ? rc : count; >> +} >> + >> /* always return newly allocated name, caller must free after use */ >> static const char *safe_name(struct kobject *kobj, const char *orig_name) >> { >> @@ -79,6 +142,12 @@ int __of_add_property_sysfs(struct device_node *np, struct property *pp) >> pp->attr.size = secure ? 0 : pp->length; >> pp->attr.read = of_node_property_read; >> >> + if (!strcmp(pp->name, "status") && of_property_read_bool(np, "dynamic")) { >> + pp->attr.attr.mode |= 0200; >> + pp->attr.write = of_node_status_write; >> + pp->attr.growable = true; >> + } >> + >> rc = sysfs_create_bin_file(&np->kobj, &pp->attr); >> WARN(rc, "error adding attribute %s to node %pOF\n", pp->name, np); >> return rc; >>
Hi Rob, On 10/11/21 8:58 AM, Frank Rowand wrote: > Hi Matt, Greg, That was meant to be Rob, not Matt. -Frank > > On 10/8/21 1:51 PM, Frank Rowand wrote: >> On 10/6/21 7:09 PM, Zev Weiss wrote: >>> Nodes marked with this (boolean) property will have a writable status >>> sysfs file, which can be used to toggle them between "okay" and >>> "reserved", effectively hot-plugging them. Note that this will only >>> be effective for devices on busses that register for OF reconfig >>> notifications (currently spi, i2c, and platform), and only if >>> CONFIG_OF_DYNAMIC is enabled. >>> >>> Signed-off-by: Zev Weiss <zev@bewilderbeest.net> >>> --- >>> drivers/of/kobj.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++ >>> 1 file changed, 69 insertions(+) >>> >>> diff --git a/drivers/of/kobj.c b/drivers/of/kobj.c >>> index 378cb421aae1..141ae23f3130 100644 >>> --- a/drivers/of/kobj.c >>> +++ b/drivers/of/kobj.c >>> @@ -36,6 +36,69 @@ static ssize_t of_node_property_read(struct file *filp, struct kobject *kobj, >>> return memory_read_from_buffer(buf, count, &offset, pp->value, pp->length); >>> } >>> >>> +static ssize_t of_node_status_write(struct file *filp, struct kobject *kobj, >>> + struct bin_attribute *bin_attr, char *buf, >>> + loff_t offset, size_t count) >>> +{ >>> + int rc; >>> + char *newstatus; >>> + struct property **deadprev; >>> + struct property *newprop = NULL; >>> + struct property *oldprop = container_of(bin_attr, struct property, attr); >>> + struct device_node *np = container_of(kobj, struct device_node, kobj); >>> + >>> + if (WARN_ON_ONCE(strcmp(oldprop->name, "status"))) >>> + return -EIO; >>> + >>> + if (offset) >>> + return -EINVAL; >>> + >>> + if (sysfs_buf_streq(buf, count, "okay") || sysfs_buf_streq(buf, count, "ok")) >>> + newstatus = "okay"; >>> + else if (sysfs_buf_streq(buf, count, "reserved")) >>> + newstatus = "reserved"; >>> + else if (sysfs_buf_streq(buf, count, "disabled")) >>> + newstatus = "disabled"; >>> + else >>> + return -EINVAL; >>> + >>> + if (!strcmp(newstatus, oldprop->value)) >>> + return count; >>> + >> >> If the general approach of this patch set is the correct way to provide the desired >> functionality (I'm still pondering that), then a version of the following code > > After pondering, this approach does not appear workable to me. > > If we allow one property to be writable via sysfs we open the door for any property to > be writable from sysfs. This will likely lead to a desire to modify more than one > related property as a single transaction (so that the changes occur as a single > transaction, under a single lock event, with a single notification after all > of the properties are modified). This is not meant to be an exhaustive list of > the issues that have already been thought through in the context of overlays > (though not all of the issues have been addressed with overlays, at least many > of them, such as one transaction to apply an entire overlay, have been.) > > I don't want to make this a long missive, but will at least note the next > issue that popped up in my pondering, which is complications from modifying > the same items in a devicetree via different methods, such as both writing > to sysfs and applying/removing overlays. If the problems in the previous > paragraph are not sufficient to prevent the sysfs approach then I can > elaborate further on these additional issues. > > So another approach is needed. I have no yet thought this through, but I > have an alternative. First, change the new property name from "dynamic" > to something more descriptive like "ownership_shifts_between_os_and_others" > (yes, my suggestions is way too verbose and needs to be word smithed, but > the point is to clearly state the underlying action that occurs), then > define the result of this variable to be driver specific, where the > driver is required upon probe to instantiate the device in a manner > that does not impact the other user(s) of the underlying hardware > and to use a driver specific method to transfer control of the > hardware between the os and the other user(s). I propose the method > would be via a device specific file (or set of files) in sysfs (Greg's > input invited on the use of sysfs in this manner - if I recall correctly > this is the current preferred mechanism). > > -Frank > > >> probably belongs in drivers/of/dynamic.c so that it is easier to maintain and keep >> consistent with other dynamic devicetree updates. If you look at the code there >> that touches deadprops (eg __of_changeset_entry_apply()) you will notice that the >> locking issues are more extensive than what is implemented here. >> >> I'm still thinking about how this interacts with other forms of dynamic devicetree >> changes (eg drivers/of/dynamic.c and also overlays). >> >>> + /* >>> + * of_update_property_self() doesn't free replaced properties, so >>> + * rifle through deadprops first to see if there's an equivalent old >>> + * status property we can reuse instead of allocating a new one. >>> + */ >>> + mutex_lock(&of_mutex); >>> + for (deadprev = &np->deadprops; *deadprev; deadprev = &(*deadprev)->next) { >>> + struct property *deadprop = *deadprev; >>> + if (!strcmp(deadprop->name, "status") && >>> + deadprop->length == strlen(newstatus) + 1 && >>> + !strcmp(deadprop->value, newstatus)) { >>> + *deadprev = deadprop->next; >>> + deadprop->next = NULL; >>> + newprop = deadprop; >>> + break; >>> + } >>> + } >>> + mutex_unlock(&of_mutex); >>> + >>> + if (!newprop) { >>> + newprop = kzalloc(sizeof(*newprop), GFP_KERNEL); >>> + if (!newprop) >>> + return -ENOMEM; >>> + >>> + newprop->name = oldprop->name; >>> + newprop->value = newstatus; >>> + newprop->length = strlen(newstatus) + 1; >>> + } >>> + >>> + rc = of_update_property_self(np, newprop, true); >> >> -Frank >> >>> + >>> + return rc ? rc : count; >>> +} >>> + >>> /* always return newly allocated name, caller must free after use */ >>> static const char *safe_name(struct kobject *kobj, const char *orig_name) >>> { >>> @@ -79,6 +142,12 @@ int __of_add_property_sysfs(struct device_node *np, struct property *pp) >>> pp->attr.size = secure ? 0 : pp->length; >>> pp->attr.read = of_node_property_read; >>> >>> + if (!strcmp(pp->name, "status") && of_property_read_bool(np, "dynamic")) { >>> + pp->attr.attr.mode |= 0200; >>> + pp->attr.write = of_node_status_write; >>> + pp->attr.growable = true; >>> + } >>> + >>> rc = sysfs_create_bin_file(&np->kobj, &pp->attr); >>> WARN(rc, "error adding attribute %s to node %pOF\n", pp->name, np); >>> return rc; >>>
Hi Frank, Thanks for the thorough consideration on this. (More inline below.) On Mon, Oct 11, 2021 at 06:58:32AM PDT, Frank Rowand wrote: >Hi Matt, Greg, > >On 10/8/21 1:51 PM, Frank Rowand wrote: >> On 10/6/21 7:09 PM, Zev Weiss wrote: >>> Nodes marked with this (boolean) property will have a writable status >>> sysfs file, which can be used to toggle them between "okay" and >>> "reserved", effectively hot-plugging them. Note that this will only >>> be effective for devices on busses that register for OF reconfig >>> notifications (currently spi, i2c, and platform), and only if >>> CONFIG_OF_DYNAMIC is enabled. >>> >>> Signed-off-by: Zev Weiss <zev@bewilderbeest.net> >>> --- >>> drivers/of/kobj.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++ >>> 1 file changed, 69 insertions(+) >>> >>> diff --git a/drivers/of/kobj.c b/drivers/of/kobj.c >>> index 378cb421aae1..141ae23f3130 100644 >>> --- a/drivers/of/kobj.c >>> +++ b/drivers/of/kobj.c >>> @@ -36,6 +36,69 @@ static ssize_t of_node_property_read(struct file *filp, struct kobject *kobj, >>> return memory_read_from_buffer(buf, count, &offset, pp->value, pp->length); >>> } >>> >>> +static ssize_t of_node_status_write(struct file *filp, struct kobject *kobj, >>> + struct bin_attribute *bin_attr, char *buf, >>> + loff_t offset, size_t count) >>> +{ >>> + int rc; >>> + char *newstatus; >>> + struct property **deadprev; >>> + struct property *newprop = NULL; >>> + struct property *oldprop = container_of(bin_attr, struct property, attr); >>> + struct device_node *np = container_of(kobj, struct device_node, kobj); >>> + >>> + if (WARN_ON_ONCE(strcmp(oldprop->name, "status"))) >>> + return -EIO; >>> + >>> + if (offset) >>> + return -EINVAL; >>> + >>> + if (sysfs_buf_streq(buf, count, "okay") || sysfs_buf_streq(buf, count, "ok")) >>> + newstatus = "okay"; >>> + else if (sysfs_buf_streq(buf, count, "reserved")) >>> + newstatus = "reserved"; >>> + else if (sysfs_buf_streq(buf, count, "disabled")) >>> + newstatus = "disabled"; >>> + else >>> + return -EINVAL; >>> + >>> + if (!strcmp(newstatus, oldprop->value)) >>> + return count; >>> + >> >> If the general approach of this patch set is the correct way to provide the desired >> functionality (I'm still pondering that), then a version of the following code > >After pondering, this approach does not appear workable to me. > Okay -- I had come to a similar conclusion, if for slightly different reasons (basically, just that the sets of "things that would avoid binary sysfs attr abuse" and "things that would maintain userspace compatibility" seemed pretty disjoint). > <snip> > >So another approach is needed. I have no yet thought this through, but I >have an alternative. First, change the new property name from "dynamic" >to something more descriptive like "ownership_shifts_between_os_and_others" >(yes, my suggestions is way too verbose and needs to be word smithed, but >the point is to clearly state the underlying action that occurs), then >define the result of this variable to be driver specific, where the >driver is required upon probe to instantiate the device in a manner >that does not impact the other user(s) of the underlying hardware >and to use a driver specific method to transfer control of the >hardware between the os and the other user(s). I propose the method >would be via a device specific file (or set of files) in sysfs (Greg's >input invited on the use of sysfs in this manner - if I recall correctly >this is the current preferred mechanism). > I'm not sure if you've had a chance to take a look at it already, but this sounds fairly similar to the approach I took in the semi-prequel series that preceded this one: https://lore.kernel.org/openbmc/20210929115409.21254-1-zev@bewilderbeest.net/ The general idea there was to start making use of the "reserved" status value (defined in the DT spec but thus far not really implemented anywhere that I'm aware of) instead of introducing a new property. The implementation in that series was very driver-specific (probably overly so), but I think could be generalized somewhat in a couple directions without an enormous amount of additional work. First (top-down), we could have the driver core avoid automatically binding drivers for reserved devices. Second (bottom-up), the machinery implemented in the aspeed-smc driver in that series could be lifted into the MTD spi-nor framework as suggested by Dhananjay. Rob, Greg -- do you think another version of that patch series with those changes might be a viable strategy? Thanks, Zev
diff --git a/drivers/of/kobj.c b/drivers/of/kobj.c index 378cb421aae1..141ae23f3130 100644 --- a/drivers/of/kobj.c +++ b/drivers/of/kobj.c @@ -36,6 +36,69 @@ static ssize_t of_node_property_read(struct file *filp, struct kobject *kobj, return memory_read_from_buffer(buf, count, &offset, pp->value, pp->length); } +static ssize_t of_node_status_write(struct file *filp, struct kobject *kobj, + struct bin_attribute *bin_attr, char *buf, + loff_t offset, size_t count) +{ + int rc; + char *newstatus; + struct property **deadprev; + struct property *newprop = NULL; + struct property *oldprop = container_of(bin_attr, struct property, attr); + struct device_node *np = container_of(kobj, struct device_node, kobj); + + if (WARN_ON_ONCE(strcmp(oldprop->name, "status"))) + return -EIO; + + if (offset) + return -EINVAL; + + if (sysfs_buf_streq(buf, count, "okay") || sysfs_buf_streq(buf, count, "ok")) + newstatus = "okay"; + else if (sysfs_buf_streq(buf, count, "reserved")) + newstatus = "reserved"; + else if (sysfs_buf_streq(buf, count, "disabled")) + newstatus = "disabled"; + else + return -EINVAL; + + if (!strcmp(newstatus, oldprop->value)) + return count; + + /* + * of_update_property_self() doesn't free replaced properties, so + * rifle through deadprops first to see if there's an equivalent old + * status property we can reuse instead of allocating a new one. + */ + mutex_lock(&of_mutex); + for (deadprev = &np->deadprops; *deadprev; deadprev = &(*deadprev)->next) { + struct property *deadprop = *deadprev; + if (!strcmp(deadprop->name, "status") && + deadprop->length == strlen(newstatus) + 1 && + !strcmp(deadprop->value, newstatus)) { + *deadprev = deadprop->next; + deadprop->next = NULL; + newprop = deadprop; + break; + } + } + mutex_unlock(&of_mutex); + + if (!newprop) { + newprop = kzalloc(sizeof(*newprop), GFP_KERNEL); + if (!newprop) + return -ENOMEM; + + newprop->name = oldprop->name; + newprop->value = newstatus; + newprop->length = strlen(newstatus) + 1; + } + + rc = of_update_property_self(np, newprop, true); + + return rc ? rc : count; +} + /* always return newly allocated name, caller must free after use */ static const char *safe_name(struct kobject *kobj, const char *orig_name) { @@ -79,6 +142,12 @@ int __of_add_property_sysfs(struct device_node *np, struct property *pp) pp->attr.size = secure ? 0 : pp->length; pp->attr.read = of_node_property_read; + if (!strcmp(pp->name, "status") && of_property_read_bool(np, "dynamic")) { + pp->attr.attr.mode |= 0200; + pp->attr.write = of_node_status_write; + pp->attr.growable = true; + } + rc = sysfs_create_bin_file(&np->kobj, &pp->attr); WARN(rc, "error adding attribute %s to node %pOF\n", pp->name, np); return rc;
Nodes marked with this (boolean) property will have a writable status sysfs file, which can be used to toggle them between "okay" and "reserved", effectively hot-plugging them. Note that this will only be effective for devices on busses that register for OF reconfig notifications (currently spi, i2c, and platform), and only if CONFIG_OF_DYNAMIC is enabled. Signed-off-by: Zev Weiss <zev@bewilderbeest.net> --- drivers/of/kobj.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+)