diff mbox

[v2,2/3] platform/chrome: Support reading/writing the vboot context

Message ID 1442234049-18637-3-git-send-email-emilio.lopez@collabora.co.uk
State New, archived
Headers show

Commit Message

Emilio López Sept. 14, 2015, 12:34 p.m. UTC
Some EC implementations include a small nvram space used to store
verified boot context data. This patch offers a way to expose this
data to userspace.

Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk>
---
Changes from v1:
 - Use is_bin_visible instead of is_visible

 Documentation/devicetree/bindings/mfd/cros-ec.txt |   4 +
 drivers/platform/chrome/Makefile                  |   5 +-
 drivers/platform/chrome/cros_ec_dev.c             |   1 +
 drivers/platform/chrome/cros_ec_vbc.c             | 137 ++++++++++++++++++++++
 include/linux/mfd/cros_ec.h                       |   1 +
 5 files changed, 147 insertions(+), 1 deletion(-)
 create mode 100644 drivers/platform/chrome/cros_ec_vbc.c

Comments

Javier Martinez Canillas Sept. 15, 2015, 1:47 p.m. UTC | #1
Hello Emilio,

Patch looks mostly good to me, I just have a few comments.

On Mon, Sep 14, 2015 at 2:34 PM, Emilio López
<emilio.lopez@collabora.co.uk> wrote:
> Some EC implementations include a small nvram space used to store
> verified boot context data. This patch offers a way to expose this
> data to userspace.
>
> Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk>
> ---
> Changes from v1:
>  - Use is_bin_visible instead of is_visible
>
>  Documentation/devicetree/bindings/mfd/cros-ec.txt |   4 +
>  drivers/platform/chrome/Makefile                  |   5 +-
>  drivers/platform/chrome/cros_ec_dev.c             |   1 +
>  drivers/platform/chrome/cros_ec_vbc.c             | 137 ++++++++++++++++++++++
>  include/linux/mfd/cros_ec.h                       |   1 +
>  5 files changed, 147 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/platform/chrome/cros_ec_vbc.c
>
> diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt b/Documentation/devicetree/bindings/mfd/cros-ec.txt
> index 1777916..136e0c2 100644
> --- a/Documentation/devicetree/bindings/mfd/cros-ec.txt
> +++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt
> @@ -34,6 +34,10 @@ Required properties (LPC):
>  - compatible: "google,cros-ec-lpc"
>  - reg: List of (IO address, size) pairs defining the interface uses
>
> +Optional properties (all):
> +- google,has-vbc-nvram: Some implementations of the EC include a small
> +  nvram space used to store verified boot context data. This boolean flag
> +  is used to specify whether this nvram is present or not.
>
>  Example for I2C:
>

I would split the DT binding part from the actual implementation, see
Documentation/devicetree/bindings/submitting-patches.txt.

> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
> index 4a11b01..787be61 100644
> --- a/drivers/platform/chrome/Makefile
> +++ b/drivers/platform/chrome/Makefile
> @@ -1,7 +1,10 @@
>
>  obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
>  obj-$(CONFIG_CHROMEOS_PSTORE)  += chromeos_pstore.o
> -cros_ec_devs-objs               := cros_ec_dev.o cros_ec_sysfs.o cros_ec_lightbar.o
> +cros_ec_devs-objs               := cros_ec_dev.o
> +cros_ec_devs-objs               += cros_ec_lightbar.o
> +cros_ec_devs-objs               += cros_ec_sysfs.o
> +cros_ec_devs-objs               += cros_ec_vbc.o

Why are you changing the Makefile? AFAIK += is usually used when the
compilation is conditional based on a Kconfig symbol but since these
are build unconditionally, I'll just keep it as foo := bar baz

Which makes me think, do we need a Kconfig option for this feature
since not all machines have it?

>  obj-$(CONFIG_CROS_EC_CHARDEV)   += cros_ec_devs.o
>  obj-$(CONFIG_CROS_EC_LPC)       += cros_ec_lpc.o
>  obj-$(CONFIG_CROS_EC_PROTO)    += cros_ec_proto.o
> diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c
> index e8fcdc2..d19263f 100644
> --- a/drivers/platform/chrome/cros_ec_dev.c
> +++ b/drivers/platform/chrome/cros_ec_dev.c
> @@ -32,6 +32,7 @@ static int ec_major;
>  static const struct attribute_group *cros_ec_groups[] = {
>         &cros_ec_attr_group,
>         &cros_ec_lightbar_attr_group,
> +       &cros_ec_vbc_attr_group,
>         NULL,
>  };
>
> diff --git a/drivers/platform/chrome/cros_ec_vbc.c b/drivers/platform/chrome/cros_ec_vbc.c
> new file mode 100644
> index 0000000..a0e8d38
> --- /dev/null
> +++ b/drivers/platform/chrome/cros_ec_vbc.c
> @@ -0,0 +1,137 @@
> +/*
> + * cros_ec_vbc - Expose the vboot context nvram to userspace
> + *
> + * Copyright (C) 2015 Collabora Ltd.
> + *
> + * based on vendor driver,
> + *
> + * Copyright (C) 2012 The Chromium OS Authors
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/mfd/cros_ec.h>
> +#include <linux/mfd/cros_ec_commands.h>
> +#include <linux/slab.h>
> +
> +static ssize_t vboot_context_read(struct file *filp, struct kobject *kobj,
> +                                 struct bin_attribute *att, char *buf,
> +                                 loff_t pos, size_t count)
> +{
> +       struct device *dev = container_of(kobj, struct device, kobj);
> +       struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
> +                                             class_dev);
> +       struct cros_ec_device *ecdev = ec->ec_dev;
> +       struct ec_params_vbnvcontext *params;
> +       struct cros_ec_command *msg;
> +       int err;
> +       const size_t para_sz = sizeof(struct ec_params_vbnvcontext);
> +       const size_t resp_sz = sizeof(struct ec_response_vbnvcontext);
> +       const size_t payload = max(para_sz, resp_sz);
> +
> +       msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL);
> +       if (!msg)
> +               return -ENOMEM;
> +
> +       params = (struct ec_params_vbnvcontext *)msg->data;
> +       params->op = EC_VBNV_CONTEXT_OP_READ;
> +
> +       msg->version = EC_VER_VBNV_CONTEXT;
> +       msg->command = EC_CMD_VBNV_CONTEXT;
> +       msg->outsize = sizeof(params->op);

Shouldn't this be para_sz ? Since you are sending to the EC the whole
struct ec_params_vbnvcontext and not only the op field.

Or if the EC only expects to get the u32 op field, then I think your
max payload calculation is not correct.

> +       msg->insize = resp_sz;
> +
> +       err = cros_ec_cmd_xfer(ecdev, msg);
> +       if (err < 0) {
> +               dev_err(dev, "Error sending read request: %d\n", err);
> +               kfree(msg);
> +               return err;
> +       }
> +
> +       BUILD_BUG_ON(resp_sz > PAGE_SIZE);

Why you need this? struct ec_response_vbnvcontext is really small AFAICT.

> +       memcpy(buf, msg->data, resp_sz);
> +
> +       kfree(msg);
> +       return resp_sz;
> +}
> +
> +static ssize_t vboot_context_write(struct file *filp, struct kobject *kobj,
> +                                  struct bin_attribute *attr, char *buf,
> +                                  loff_t pos, size_t count)
> +{
> +       struct device *dev = container_of(kobj, struct device, kobj);
> +       struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
> +                                             class_dev);
> +       struct cros_ec_device *ecdev = ec->ec_dev;
> +       struct ec_params_vbnvcontext *params;
> +       struct cros_ec_command *msg;
> +       int err;
> +       const size_t para_sz = sizeof(*params);
> +       const size_t data_sz = sizeof(params->block);
> +
> +       /* Only write full values */
> +       if (count != data_sz)
> +               return -EINVAL;
> +
> +       msg = kmalloc(sizeof(*msg) + para_sz, GFP_KERNEL);
> +       if (!msg)
> +               return -ENOMEM;
> +
> +       params = (struct ec_params_vbnvcontext *)msg->data;
> +       params->op = EC_VBNV_CONTEXT_OP_WRITE;
> +       memcpy(params->block, buf, data_sz);
> +
> +       msg->version = EC_VER_VBNV_CONTEXT;
> +       msg->command = EC_CMD_VBNV_CONTEXT;
> +       msg->outsize = para_sz;
> +       msg->insize = 0;
> +
> +       err = cros_ec_cmd_xfer(ecdev, msg);
> +       if (err < 0) {
> +               dev_err(dev, "Error sending write request: %d\n", err);
> +               kfree(msg);
> +               return err;
> +       }
> +
> +       kfree(msg);
> +       return data_sz;
> +}
> +
> +static umode_t cros_ec_vbc_is_visible(struct kobject *kobj,
> +                                     struct bin_attribute *a, int n)
> +{
> +       struct device *dev = container_of(kobj, struct device, kobj);
> +       struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
> +                                             class_dev);
> +       struct device_node *np = ec->ec_dev->dev->of_node;
> +
> +       if (IS_ENABLED(CONFIG_OF) && np) {
> +               if (of_property_read_bool(np, "google,has-vbc-nvram"))
> +                       return a->attr.mode;
> +       }
> +
> +       return 0;
> +}
> +
> +static BIN_ATTR_RW(vboot_context, 16);
> +
> +static struct bin_attribute *cros_ec_vbc_bin_attrs[] = {
> +       &bin_attr_vboot_context,
> +       NULL
> +};
> +
> +struct attribute_group cros_ec_vbc_attr_group = {
> +       .name = "vbc",
> +       .bin_attrs = cros_ec_vbc_bin_attrs,
> +       .is_bin_visible = cros_ec_vbc_is_visible,
> +};
> diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
> index da72671..494682c 100644
> --- a/include/linux/mfd/cros_ec.h
> +++ b/include/linux/mfd/cros_ec.h
> @@ -255,5 +255,6 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev);
>  /* sysfs stuff */
>  extern struct attribute_group cros_ec_attr_group;
>  extern struct attribute_group cros_ec_lightbar_attr_group;
> +extern struct attribute_group cros_ec_vbc_attr_group;
>
>  #endif /* __LINUX_MFD_CROS_EC_H */
> --
> 2.1.4

Best regards,
Javier
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Emilio López Sept. 15, 2015, 7:16 p.m. UTC | #2
Hi Javier,

Thanks for the review. You'll find my answers inline

On 15/09/15 10:47, Javier Martinez Canillas wrote:
> Hello Emilio,
>
> Patch looks mostly good to me, I just have a few comments.
>
> On Mon, Sep 14, 2015 at 2:34 PM, Emilio López
> <emilio.lopez@collabora.co.uk> wrote:
>> Some EC implementations include a small nvram space used to store
>> verified boot context data. This patch offers a way to expose this
>> data to userspace.
>>
>> Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk>
>> ---
>> Changes from v1:
>>   - Use is_bin_visible instead of is_visible
>>
>>   Documentation/devicetree/bindings/mfd/cros-ec.txt |   4 +
>>   drivers/platform/chrome/Makefile                  |   5 +-
>>   drivers/platform/chrome/cros_ec_dev.c             |   1 +
>>   drivers/platform/chrome/cros_ec_vbc.c             | 137 ++++++++++++++++++++++
>>   include/linux/mfd/cros_ec.h                       |   1 +
>>   5 files changed, 147 insertions(+), 1 deletion(-)
>>   create mode 100644 drivers/platform/chrome/cros_ec_vbc.c
>>
>> diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt b/Documentation/devicetree/bindings/mfd/cros-ec.txt
>> index 1777916..136e0c2 100644
>> --- a/Documentation/devicetree/bindings/mfd/cros-ec.txt
>> +++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt
>> @@ -34,6 +34,10 @@ Required properties (LPC):
>>   - compatible: "google,cros-ec-lpc"
>>   - reg: List of (IO address, size) pairs defining the interface uses
>>
>> +Optional properties (all):
>> +- google,has-vbc-nvram: Some implementations of the EC include a small
>> +  nvram space used to store verified boot context data. This boolean flag
>> +  is used to specify whether this nvram is present or not.
>>
>>   Example for I2C:
>>
>
> I would split the DT binding part from the actual implementation, see
> Documentation/devicetree/bindings/submitting-patches.txt.

Ok, I'll do

>> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
>> index 4a11b01..787be61 100644
>> --- a/drivers/platform/chrome/Makefile
>> +++ b/drivers/platform/chrome/Makefile
>> @@ -1,7 +1,10 @@
>>
>>   obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
>>   obj-$(CONFIG_CHROMEOS_PSTORE)  += chromeos_pstore.o
>> -cros_ec_devs-objs               := cros_ec_dev.o cros_ec_sysfs.o cros_ec_lightbar.o
>> +cros_ec_devs-objs               := cros_ec_dev.o
>> +cros_ec_devs-objs               += cros_ec_lightbar.o
>> +cros_ec_devs-objs               += cros_ec_sysfs.o
>> +cros_ec_devs-objs               += cros_ec_vbc.o
>
> Why are you changing the Makefile? AFAIK += is usually used when the
> compilation is conditional based on a Kconfig symbol but since these
> are build unconditionally, I'll just keep it as foo := bar baz

As far as I'm aware, += is append[0]. It's used for stuff like
obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
because the left part will resolve to "obj-y" or similar, and you want 
to add to it, not replace it. I only changed the Makefile here because 
the line was growing too long, and I thought it looked neater this way; 
it shouldn't cause any functional change apart from the intended one.

[0] https://www.gnu.org/software/make/manual/html_node/Appending.html

> Which makes me think, do we need a Kconfig option for this feature
> since not all machines have it?

Not all machines have a lightbar either; both of the features are 
runtime-conditional. IMO, it makes more sense this way when you consider 
a kernel will likely support multiple platforms.

>>   obj-$(CONFIG_CROS_EC_CHARDEV)   += cros_ec_devs.o
>>   obj-$(CONFIG_CROS_EC_LPC)       += cros_ec_lpc.o
>>   obj-$(CONFIG_CROS_EC_PROTO)    += cros_ec_proto.o
>> diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c
>> index e8fcdc2..d19263f 100644
>> --- a/drivers/platform/chrome/cros_ec_dev.c
>> +++ b/drivers/platform/chrome/cros_ec_dev.c
>> @@ -32,6 +32,7 @@ static int ec_major;
>>   static const struct attribute_group *cros_ec_groups[] = {
>>          &cros_ec_attr_group,
>>          &cros_ec_lightbar_attr_group,
>> +       &cros_ec_vbc_attr_group,
>>          NULL,
>>   };
>>
>> diff --git a/drivers/platform/chrome/cros_ec_vbc.c b/drivers/platform/chrome/cros_ec_vbc.c
>> new file mode 100644
>> index 0000000..a0e8d38
>> --- /dev/null
>> +++ b/drivers/platform/chrome/cros_ec_vbc.c
>> @@ -0,0 +1,137 @@
>> +/*
>> + * cros_ec_vbc - Expose the vboot context nvram to userspace
>> + *
>> + * Copyright (C) 2015 Collabora Ltd.
>> + *
>> + * based on vendor driver,
>> + *
>> + * Copyright (C) 2012 The Chromium OS Authors
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License as published by
>> + * the Free Software Foundation; either version 2 of the License, or
>> + * (at your option) any later version.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/mfd/cros_ec.h>
>> +#include <linux/mfd/cros_ec_commands.h>
>> +#include <linux/slab.h>
>> +
>> +static ssize_t vboot_context_read(struct file *filp, struct kobject *kobj,
>> +                                 struct bin_attribute *att, char *buf,
>> +                                 loff_t pos, size_t count)
>> +{
>> +       struct device *dev = container_of(kobj, struct device, kobj);
>> +       struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
>> +                                             class_dev);
>> +       struct cros_ec_device *ecdev = ec->ec_dev;
>> +       struct ec_params_vbnvcontext *params;
>> +       struct cros_ec_command *msg;
>> +       int err;
>> +       const size_t para_sz = sizeof(struct ec_params_vbnvcontext);
>> +       const size_t resp_sz = sizeof(struct ec_response_vbnvcontext);
>> +       const size_t payload = max(para_sz, resp_sz);
>> +
>> +       msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL);
>> +       if (!msg)
>> +               return -ENOMEM;
>> +
>> +       params = (struct ec_params_vbnvcontext *)msg->data;
>> +       params->op = EC_VBNV_CONTEXT_OP_READ;
>> +
>> +       msg->version = EC_VER_VBNV_CONTEXT;
>> +       msg->command = EC_CMD_VBNV_CONTEXT;
>> +       msg->outsize = sizeof(params->op);
>
> Shouldn't this be para_sz ? Since you are sending to the EC the whole
> struct ec_params_vbnvcontext and not only the op field.
>
> Or if the EC only expects to get the u32 op field, then I think your
> max payload calculation is not correct.

The params struct is the same for both read and write ops, so it has the 
op flag and a buffer for the write op. During the read op I believe 
there's no need to send this potentially-garbage-filled buffer to the 
EC, so outsize is set accordingly here.

The vendor tree does it this way, but I can change it to send the full 
buffer if you prefer so.

ec code is at 
https://chromium.googlesource.com/chromiumos/platform/ec/+/master/common/system.c 
L1086+ if you want to take a look

>> +       msg->insize = resp_sz;
>> +
>> +       err = cros_ec_cmd_xfer(ecdev, msg);
>> +       if (err < 0) {
>> +               dev_err(dev, "Error sending read request: %d\n", err);
>> +               kfree(msg);
>> +               return err;
>> +       }
>> +
>> +       BUILD_BUG_ON(resp_sz > PAGE_SIZE);
>
> Why you need this? struct ec_response_vbnvcontext is really small AFAICT.

This is just me being paranoid about memcpy :) Indeed, the struct should 
be way smaller than a page. I can drop it if you think it's too much.

>> +       memcpy(buf, msg->data, resp_sz);
>> +
>> +       kfree(msg);
>> +       return resp_sz;
>> +}
>> +

Thanks!
Emilio
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Javier Martinez Canillas Sept. 15, 2015, 7:43 p.m. UTC | #3
Hello Emilio,

On Tue, Sep 15, 2015 at 9:16 PM, Emilio López
<emilio.lopez@collabora.co.uk> wrote:

[snip]

>>>
>>>   obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
>>>   obj-$(CONFIG_CHROMEOS_PSTORE)  += chromeos_pstore.o
>>> -cros_ec_devs-objs               := cros_ec_dev.o cros_ec_sysfs.o
>>> cros_ec_lightbar.o
>>> +cros_ec_devs-objs               := cros_ec_dev.o
>>> +cros_ec_devs-objs               += cros_ec_lightbar.o
>>> +cros_ec_devs-objs               += cros_ec_sysfs.o
>>> +cros_ec_devs-objs               += cros_ec_vbc.o
>>
>>
>> Why are you changing the Makefile? AFAIK += is usually used when the
>> compilation is conditional based on a Kconfig symbol but since these
>> are build unconditionally, I'll just keep it as foo := bar baz
>
>
> As far as I'm aware, += is append[0]. It's used for stuff like
> obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
> because the left part will resolve to "obj-y" or similar, and you want to
> add to it, not replace it. I only changed the Makefile here because the line
> was growing too long, and I thought it looked neater this way; it shouldn't
> cause any functional change apart from the intended one.
>
> [0] https://www.gnu.org/software/make/manual/html_node/Appending.html
>

Yes, I know how Kbuild works. What I tried to say is that you usually
append based on a Kconfig symbol. In fact even you are mentioning such
an example.
So appending unconditionally like you are doing makes the Makefile
harder to read IMHO. If the line grows to long you can use a backlash
(\) char to split the line.

>> Which makes me think, do we need a Kconfig option for this feature
>> since not all machines have it?
>
>
> Not all machines have a lightbar either; both of the features are
> runtime-conditional. IMO, it makes more sense this way when you consider a
> kernel will likely support multiple platforms.
>

Ok, thanks for the clarification.

>
>>>   obj-$(CONFIG_CROS_EC_CHARDEV)   += cros_ec_devs.o
>>>   obj-$(CONFIG_CROS_EC_LPC)       += cros_ec_lpc.o
>>>   obj-$(CONFIG_CROS_EC_PROTO)    += cros_ec_proto.o
>>> diff --git a/drivers/platform/chrome/cros_ec_dev.c
>>> b/drivers/platform/chrome/cros_ec_dev.c
>>> index e8fcdc2..d19263f 100644
>>> --- a/drivers/platform/chrome/cros_ec_dev.c
>>> +++ b/drivers/platform/chrome/cros_ec_dev.c
>>> @@ -32,6 +32,7 @@ static int ec_major;
>>>   static const struct attribute_group *cros_ec_groups[] = {
>>>          &cros_ec_attr_group,
>>>          &cros_ec_lightbar_attr_group,
>>> +       &cros_ec_vbc_attr_group,
>>>          NULL,
>>>   };
>>>
>>> diff --git a/drivers/platform/chrome/cros_ec_vbc.c
>>> b/drivers/platform/chrome/cros_ec_vbc.c
>>> new file mode 100644
>>> index 0000000..a0e8d38
>>> --- /dev/null
>>> +++ b/drivers/platform/chrome/cros_ec_vbc.c
>>> @@ -0,0 +1,137 @@
>>> +/*
>>> + * cros_ec_vbc - Expose the vboot context nvram to userspace
>>> + *
>>> + * Copyright (C) 2015 Collabora Ltd.
>>> + *
>>> + * based on vendor driver,
>>> + *
>>> + * Copyright (C) 2012 The Chromium OS Authors
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License as published by
>>> + * the Free Software Foundation; either version 2 of the License, or
>>> + * (at your option) any later version.
>>> + *
>>> + * This program is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> + * GNU General Public License for more details.
>>> + */
>>> +
>>> +#include <linux/of.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/mfd/cros_ec.h>
>>> +#include <linux/mfd/cros_ec_commands.h>
>>> +#include <linux/slab.h>
>>> +
>>> +static ssize_t vboot_context_read(struct file *filp, struct kobject
>>> *kobj,
>>> +                                 struct bin_attribute *att, char *buf,
>>> +                                 loff_t pos, size_t count)
>>> +{
>>> +       struct device *dev = container_of(kobj, struct device, kobj);
>>> +       struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
>>> +                                             class_dev);
>>> +       struct cros_ec_device *ecdev = ec->ec_dev;
>>> +       struct ec_params_vbnvcontext *params;
>>> +       struct cros_ec_command *msg;
>>> +       int err;
>>> +       const size_t para_sz = sizeof(struct ec_params_vbnvcontext);
>>> +       const size_t resp_sz = sizeof(struct ec_response_vbnvcontext);
>>> +       const size_t payload = max(para_sz, resp_sz);
>>> +
>>> +       msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL);
>>> +       if (!msg)
>>> +               return -ENOMEM;
>>> +
>>> +       params = (struct ec_params_vbnvcontext *)msg->data;
>>> +       params->op = EC_VBNV_CONTEXT_OP_READ;
>>> +
>>> +       msg->version = EC_VER_VBNV_CONTEXT;
>>> +       msg->command = EC_CMD_VBNV_CONTEXT;
>>> +       msg->outsize = sizeof(params->op);
>>
>>
>> Shouldn't this be para_sz ? Since you are sending to the EC the whole
>> struct ec_params_vbnvcontext and not only the op field.
>>
>> Or if the EC only expects to get the u32 op field, then I think your
>> max payload calculation is not correct.
>
>
> The params struct is the same for both read and write ops, so it has the op

That's not true, struct ec_response_vbnvcontext has only the block
field while struct ec_param_vbnvcontext has both the op and block
fields.

> flag and a buffer for the write op. During the read op I believe there's no
> need to send this potentially-garbage-filled buffer to the EC, so outsize is
> set accordingly here.

Yes, I agree with you but then as I mentioned I think your payload
calculation is wrong since you want instead max(sizeof(struct
ec_response_vbnvcontext), sizeof(param->op)). Otherwise you are
allocating 4 bytes more than needed.
>
> The vendor tree does it this way, but I can change it to send the full
> buffer if you prefer so.
>
> ec code is at
> https://chromium.googlesource.com/chromiumos/platform/ec/+/master/common/system.c
> L1086+ if you want to take a look
>
>>> +       msg->insize = resp_sz;
>>> +
>>> +       err = cros_ec_cmd_xfer(ecdev, msg);
>>> +       if (err < 0) {
>>> +               dev_err(dev, "Error sending read request: %d\n", err);
>>> +               kfree(msg);
>>> +               return err;
>>> +       }
>>> +
>>> +       BUILD_BUG_ON(resp_sz > PAGE_SIZE);
>>
>>
>> Why you need this? struct ec_response_vbnvcontext is really small AFAICT.
>
>
> This is just me being paranoid about memcpy :) Indeed, the struct should be
> way smaller than a page. I can drop it if you think it's too much.
>

I think it can be dropped but it's up to you.

>>> +       memcpy(buf, msg->data, resp_sz);
>>> +
>>> +       kfree(msg);
>>> +       return resp_sz;
>>> +}
>>> +
>
>
> Thanks!
> Emilio

with the needed changes, feel free to add my:

Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>

Best regards,
Javier
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Greg Kroah-Hartman Sept. 15, 2015, 8:22 p.m. UTC | #4
On Tue, Sep 15, 2015 at 09:43:35PM +0200, Javier Martinez Canillas wrote:
> Hello Emilio,
> 
> On Tue, Sep 15, 2015 at 9:16 PM, Emilio López
> <emilio.lopez@collabora.co.uk> wrote:
> 
> [snip]
> 
> >>>
> >>>   obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
> >>>   obj-$(CONFIG_CHROMEOS_PSTORE)  += chromeos_pstore.o
> >>> -cros_ec_devs-objs               := cros_ec_dev.o cros_ec_sysfs.o
> >>> cros_ec_lightbar.o
> >>> +cros_ec_devs-objs               := cros_ec_dev.o
> >>> +cros_ec_devs-objs               += cros_ec_lightbar.o
> >>> +cros_ec_devs-objs               += cros_ec_sysfs.o
> >>> +cros_ec_devs-objs               += cros_ec_vbc.o
> >>
> >>
> >> Why are you changing the Makefile? AFAIK += is usually used when the
> >> compilation is conditional based on a Kconfig symbol but since these
> >> are build unconditionally, I'll just keep it as foo := bar baz
> >
> >
> > As far as I'm aware, += is append[0]. It's used for stuff like
> > obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
> > because the left part will resolve to "obj-y" or similar, and you want to
> > add to it, not replace it. I only changed the Makefile here because the line
> > was growing too long, and I thought it looked neater this way; it shouldn't
> > cause any functional change apart from the intended one.
> >
> > [0] https://www.gnu.org/software/make/manual/html_node/Appending.html
> >
> 
> Yes, I know how Kbuild works. What I tried to say is that you usually
> append based on a Kconfig symbol. In fact even you are mentioning such
> an example.
> So appending unconditionally like you are doing makes the Makefile
> harder to read IMHO. If the line grows to long you can use a backlash
> (\) char to split the line.

Either format is just fine, don't get too picky here please.
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Emilio López Sept. 15, 2015, 8:24 p.m. UTC | #5
Hi Javier,

On 15/09/15 16:43, Javier Martinez Canillas wrote:
> Hello Emilio,
>
> On Tue, Sep 15, 2015 at 9:16 PM, Emilio López
> <emilio.lopez@collabora.co.uk> wrote:
>
> [snip]
>
>>>>
>>>>    obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
>>>>    obj-$(CONFIG_CHROMEOS_PSTORE)  += chromeos_pstore.o
>>>> -cros_ec_devs-objs               := cros_ec_dev.o cros_ec_sysfs.o
>>>> cros_ec_lightbar.o
>>>> +cros_ec_devs-objs               := cros_ec_dev.o
>>>> +cros_ec_devs-objs               += cros_ec_lightbar.o
>>>> +cros_ec_devs-objs               += cros_ec_sysfs.o
>>>> +cros_ec_devs-objs               += cros_ec_vbc.o
>>>
>>>
>>> Why are you changing the Makefile? AFAIK += is usually used when the
>>> compilation is conditional based on a Kconfig symbol but since these
>>> are build unconditionally, I'll just keep it as foo := bar baz
>>
>>
>> As far as I'm aware, += is append[0]. It's used for stuff like
>> obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
>> because the left part will resolve to "obj-y" or similar, and you want to
>> add to it, not replace it. I only changed the Makefile here because the line
>> was growing too long, and I thought it looked neater this way; it shouldn't
>> cause any functional change apart from the intended one.
>>
>> [0] https://www.gnu.org/software/make/manual/html_node/Appending.html
>>
>
> Yes, I know how Kbuild works. What I tried to say is that you usually
> append based on a Kconfig symbol. In fact even you are mentioning such
> an example.
> So appending unconditionally like you are doing makes the Makefile
> harder to read IMHO. If the line grows to long you can use a backlash
> (\) char to split the line.

I guess it just boils down to personal preference; I don't feel that 
strongly about it, I'll change it in v3

(...)
>>>> +       struct device *dev = container_of(kobj, struct device, kobj);
>>>> +       struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
>>>> +                                             class_dev);
>>>> +       struct cros_ec_device *ecdev = ec->ec_dev;
>>>> +       struct ec_params_vbnvcontext *params;
>>>> +       struct cros_ec_command *msg;
>>>> +       int err;
>>>> +       const size_t para_sz = sizeof(struct ec_params_vbnvcontext);
>>>> +       const size_t resp_sz = sizeof(struct ec_response_vbnvcontext);
>>>> +       const size_t payload = max(para_sz, resp_sz);
>>>> +
>>>> +       msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL);
>>>> +       if (!msg)
>>>> +               return -ENOMEM;
>>>> +
>>>> +       params = (struct ec_params_vbnvcontext *)msg->data;
>>>> +       params->op = EC_VBNV_CONTEXT_OP_READ;
>>>> +
>>>> +       msg->version = EC_VER_VBNV_CONTEXT;
>>>> +       msg->command = EC_CMD_VBNV_CONTEXT;
>>>> +       msg->outsize = sizeof(params->op);
>>>
>>>
>>> Shouldn't this be para_sz ? Since you are sending to the EC the whole
>>> struct ec_params_vbnvcontext and not only the op field.
>>>
>>> Or if the EC only expects to get the u32 op field, then I think your
>>> max payload calculation is not correct.
>>
>>
>> The params struct is the same for both read and write ops, so it has the op
>
> That's not true, struct ec_response_vbnvcontext has only the block
> field while struct ec_param_vbnvcontext has both the op and block
> fields.

The former is a response struct, not a params struct.

>> flag and a buffer for the write op. During the read op I believe there's no
>> need to send this potentially-garbage-filled buffer to the EC, so outsize is
>> set accordingly here.
>
> Yes, I agree with you but then as I mentioned I think your payload
> calculation is wrong since you want instead max(sizeof(struct
> ec_response_vbnvcontext), sizeof(param->op)). Otherwise you are
> allocating 4 bytes more than needed.

Yeah, I can see that. If I do that though, max(...) would be less than 
the size of the full params struct, and casting data to it could lead to 
subtle bugs in the future. I can change it and add a comment mentioning 
this, deal?

(...)

> with the needed changes, feel free to add my:
>
> Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>

Ok, thanks!

Emilio
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Javier Martinez Canillas Sept. 15, 2015, 10:26 p.m. UTC | #6
Hello Emilio,

On Tue, Sep 15, 2015 at 10:24 PM, Emilio López
<emilio.lopez@collabora.co.uk> wrote:

[snip]

>>>>> +
>>>>> +       params = (struct ec_params_vbnvcontext *)msg->data;
>>>>> +       params->op = EC_VBNV_CONTEXT_OP_READ;
>>>>> +
>>>>> +       msg->version = EC_VER_VBNV_CONTEXT;
>>>>> +       msg->command = EC_CMD_VBNV_CONTEXT;
>>>>> +       msg->outsize = sizeof(params->op);
>>>>
>>>>
>>>>
>>>> Shouldn't this be para_sz ? Since you are sending to the EC the whole
>>>> struct ec_params_vbnvcontext and not only the op field.
>>>>
>>>> Or if the EC only expects to get the u32 op field, then I think your
>>>> max payload calculation is not correct.
>>>
>>>
>>>
>>> The params struct is the same for both read and write ops, so it has the
>>> op
>>
>>
>> That's not true, struct ec_response_vbnvcontext has only the block
>> field while struct ec_param_vbnvcontext has both the op and block
>> fields.
>
>
> The former is a response struct, not a params struct.
>

I misread read/write as request/response in the previous email, sorry
about that.

>>> flag and a buffer for the write op. During the read op I believe there's
>>> no
>>> need to send this potentially-garbage-filled buffer to the EC, so outsize
>>> is
>>> set accordingly here.
>>
>>
>> Yes, I agree with you but then as I mentioned I think your payload
>> calculation is wrong since you want instead max(sizeof(struct
>> ec_response_vbnvcontext), sizeof(param->op)). Otherwise you are
>> allocating 4 bytes more than needed.
>
>
> Yeah, I can see that. If I do that though, max(...) would be less than the
> size of the full params struct, and casting data to it could lead to subtle
> bugs in the future. I can change it and add a comment mentioning this, deal?
>

But by setting outsize to sizeof(params->op) you are allocating less
than the params struct anyways in the transport driver. Take a look
for example to cros_ec_cmd_xfer_i2c():

http://lxr.free-electrons.com/source/drivers/mfd/cros_ec_i2c.c#L187

But I don't have a strong opinion on this tbh, I was just pointing out
that it's strange that max(insize,outsize) does not match
msg->{insize,outsize}.

> (...)
>
>> with the needed changes, feel free to add my:
>>
>> Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
>
>
> Ok, thanks!
>
> Emilio

Best regards,
Javier
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diff mbox

Patch

diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt b/Documentation/devicetree/bindings/mfd/cros-ec.txt
index 1777916..136e0c2 100644
--- a/Documentation/devicetree/bindings/mfd/cros-ec.txt
+++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt
@@ -34,6 +34,10 @@  Required properties (LPC):
 - compatible: "google,cros-ec-lpc"
 - reg: List of (IO address, size) pairs defining the interface uses
 
+Optional properties (all):
+- google,has-vbc-nvram: Some implementations of the EC include a small
+  nvram space used to store verified boot context data. This boolean flag
+  is used to specify whether this nvram is present or not.
 
 Example for I2C:
 
diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index 4a11b01..787be61 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -1,7 +1,10 @@ 
 
 obj-$(CONFIG_CHROMEOS_LAPTOP)	+= chromeos_laptop.o
 obj-$(CONFIG_CHROMEOS_PSTORE)	+= chromeos_pstore.o
-cros_ec_devs-objs               := cros_ec_dev.o cros_ec_sysfs.o cros_ec_lightbar.o
+cros_ec_devs-objs               := cros_ec_dev.o
+cros_ec_devs-objs               += cros_ec_lightbar.o
+cros_ec_devs-objs               += cros_ec_sysfs.o
+cros_ec_devs-objs               += cros_ec_vbc.o
 obj-$(CONFIG_CROS_EC_CHARDEV)   += cros_ec_devs.o
 obj-$(CONFIG_CROS_EC_LPC)       += cros_ec_lpc.o
 obj-$(CONFIG_CROS_EC_PROTO)	+= cros_ec_proto.o
diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c
index e8fcdc2..d19263f 100644
--- a/drivers/platform/chrome/cros_ec_dev.c
+++ b/drivers/platform/chrome/cros_ec_dev.c
@@ -32,6 +32,7 @@  static int ec_major;
 static const struct attribute_group *cros_ec_groups[] = {
 	&cros_ec_attr_group,
 	&cros_ec_lightbar_attr_group,
+	&cros_ec_vbc_attr_group,
 	NULL,
 };
 
diff --git a/drivers/platform/chrome/cros_ec_vbc.c b/drivers/platform/chrome/cros_ec_vbc.c
new file mode 100644
index 0000000..a0e8d38
--- /dev/null
+++ b/drivers/platform/chrome/cros_ec_vbc.c
@@ -0,0 +1,137 @@ 
+/*
+ * cros_ec_vbc - Expose the vboot context nvram to userspace
+ *
+ * Copyright (C) 2015 Collabora Ltd.
+ *
+ * based on vendor driver,
+ *
+ * Copyright (C) 2012 The Chromium OS Authors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/slab.h>
+
+static ssize_t vboot_context_read(struct file *filp, struct kobject *kobj,
+				  struct bin_attribute *att, char *buf,
+				  loff_t pos, size_t count)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
+					      class_dev);
+	struct cros_ec_device *ecdev = ec->ec_dev;
+	struct ec_params_vbnvcontext *params;
+	struct cros_ec_command *msg;
+	int err;
+	const size_t para_sz = sizeof(struct ec_params_vbnvcontext);
+	const size_t resp_sz = sizeof(struct ec_response_vbnvcontext);
+	const size_t payload = max(para_sz, resp_sz);
+
+	msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	params = (struct ec_params_vbnvcontext *)msg->data;
+	params->op = EC_VBNV_CONTEXT_OP_READ;
+
+	msg->version = EC_VER_VBNV_CONTEXT;
+	msg->command = EC_CMD_VBNV_CONTEXT;
+	msg->outsize = sizeof(params->op);
+	msg->insize = resp_sz;
+
+	err = cros_ec_cmd_xfer(ecdev, msg);
+	if (err < 0) {
+		dev_err(dev, "Error sending read request: %d\n", err);
+		kfree(msg);
+		return err;
+	}
+
+	BUILD_BUG_ON(resp_sz > PAGE_SIZE);
+	memcpy(buf, msg->data, resp_sz);
+
+	kfree(msg);
+	return resp_sz;
+}
+
+static ssize_t vboot_context_write(struct file *filp, struct kobject *kobj,
+				   struct bin_attribute *attr, char *buf,
+				   loff_t pos, size_t count)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
+					      class_dev);
+	struct cros_ec_device *ecdev = ec->ec_dev;
+	struct ec_params_vbnvcontext *params;
+	struct cros_ec_command *msg;
+	int err;
+	const size_t para_sz = sizeof(*params);
+	const size_t data_sz = sizeof(params->block);
+
+	/* Only write full values */
+	if (count != data_sz)
+		return -EINVAL;
+
+	msg = kmalloc(sizeof(*msg) + para_sz, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	params = (struct ec_params_vbnvcontext *)msg->data;
+	params->op = EC_VBNV_CONTEXT_OP_WRITE;
+	memcpy(params->block, buf, data_sz);
+
+	msg->version = EC_VER_VBNV_CONTEXT;
+	msg->command = EC_CMD_VBNV_CONTEXT;
+	msg->outsize = para_sz;
+	msg->insize = 0;
+
+	err = cros_ec_cmd_xfer(ecdev, msg);
+	if (err < 0) {
+		dev_err(dev, "Error sending write request: %d\n", err);
+		kfree(msg);
+		return err;
+	}
+
+	kfree(msg);
+	return data_sz;
+}
+
+static umode_t cros_ec_vbc_is_visible(struct kobject *kobj,
+				      struct bin_attribute *a, int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
+					      class_dev);
+	struct device_node *np = ec->ec_dev->dev->of_node;
+
+	if (IS_ENABLED(CONFIG_OF) && np) {
+		if (of_property_read_bool(np, "google,has-vbc-nvram"))
+			return a->attr.mode;
+	}
+
+	return 0;
+}
+
+static BIN_ATTR_RW(vboot_context, 16);
+
+static struct bin_attribute *cros_ec_vbc_bin_attrs[] = {
+	&bin_attr_vboot_context,
+	NULL
+};
+
+struct attribute_group cros_ec_vbc_attr_group = {
+	.name = "vbc",
+	.bin_attrs = cros_ec_vbc_bin_attrs,
+	.is_bin_visible = cros_ec_vbc_is_visible,
+};
diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
index da72671..494682c 100644
--- a/include/linux/mfd/cros_ec.h
+++ b/include/linux/mfd/cros_ec.h
@@ -255,5 +255,6 @@  int cros_ec_query_all(struct cros_ec_device *ec_dev);
 /* sysfs stuff */
 extern struct attribute_group cros_ec_attr_group;
 extern struct attribute_group cros_ec_lightbar_attr_group;
+extern struct attribute_group cros_ec_vbc_attr_group;
 
 #endif /* __LINUX_MFD_CROS_EC_H */