Re: [PATCH v3 1/1] platform/chrome: Poke kb_wake_angle attribute visibility when needed

Re: [PATCH v3 1/1] platform/chrome: Poke kb_wake_angle attribute visibility when needed

[Gwendal Grignou]

[+chrome-platform@lists.linux.dev]

On Mon, Nov 14, 2022 at 8:10 PM Gwendal Grignou <gwendal@chromium.org> wrote:
>
> This patch is still needed to get the attribute to be present on most machines.
> Putting the attribute in the sensor hub device is more complicated, as
> that device is not as easily findable as `cros_ec`, present in
> `/sys/class`.
>
> Gwendal.
>
> On Wed, Aug 4, 2021 at 2:31 PM Gwendal Grignou <gwendal@chromium.org> wrote:
> >
> > When the sensorhub detects 2 accelerometers, kb_wake_angle attribute
> > in the chromeos EC class device needs to be visible.
> > When detected, the sensorhub requests the class device to
> > revisit the visibility of the kb_wake_angle attribute.
> > Expose the attribute group to alter to close a potiential race between
> > cros-ec-sensorhub and cros-ec-sysfs (that creates the attribute group
> > on behalf of the class driver).
> >
> > Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
> > ---
> >  drivers/platform/chrome/cros_ec_sensorhub.c | 6 +++++-
> >  drivers/platform/chrome/cros_ec_sysfs.c     | 5 +++--
> >  include/linux/platform_data/cros_ec_proto.h | 2 ++
> >  3 files changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/platform/chrome/cros_ec_sensorhub.c b/drivers/platform/chrome/cros_ec_sensorhub.c
> > index 9c4af76a9956e..8f24ed90b229c 100644
> > --- a/drivers/platform/chrome/cros_ec_sensorhub.c
> > +++ b/drivers/platform/chrome/cros_ec_sensorhub.c
> > @@ -106,8 +106,12 @@ static int cros_ec_sensorhub_register(struct device *dev,
> >                 sensor_type[sensorhub->resp->info.type]++;
> >         }
> >
> > -       if (sensor_type[MOTIONSENSE_TYPE_ACCEL] >= 2)
> > +       if (sensor_type[MOTIONSENSE_TYPE_ACCEL] >= 2) {
> >                 ec->has_kb_wake_angle = true;
> > +               if (ec->group && sysfs_update_group(&ec->class_dev.kobj,
> > +                                                   ec->group))
> > +                       dev_warn(dev, "Unable to update cros-ec-sysfs");
> > +       }
> >
> >         if (cros_ec_check_features(ec,
> >                                    EC_FEATURE_REFINED_TABLET_MODE_HYSTERESIS)) {
> > diff --git a/drivers/platform/chrome/cros_ec_sysfs.c b/drivers/platform/chrome/cros_ec_sysfs.c
> > index f07eabcf9494c..17fe657f3ffd5 100644
> > --- a/drivers/platform/chrome/cros_ec_sysfs.c
> > +++ b/drivers/platform/chrome/cros_ec_sysfs.c
> > @@ -341,7 +341,8 @@ static int cros_ec_sysfs_probe(struct platform_device *pd)
> >         struct device *dev = &pd->dev;
> >         int ret;
> >
> > -       ret = sysfs_create_group(&ec_dev->class_dev.kobj, &cros_ec_attr_group);
> > +       ec_dev->group = &cros_ec_attr_group;
> > +       ret = sysfs_create_group(&ec_dev->class_dev.kobj, ec_dev->group);
> >         if (ret < 0)
> >                 dev_err(dev, "failed to create attributes. err=%d\n", ret);
> >
> > @@ -352,7 +353,7 @@ static int cros_ec_sysfs_remove(struct platform_device *pd)
> >  {
> >         struct cros_ec_dev *ec_dev = dev_get_drvdata(pd->dev.parent);
> >
> > -       sysfs_remove_group(&ec_dev->class_dev.kobj, &cros_ec_attr_group);
> > +       sysfs_remove_group(&ec_dev->class_dev.kobj, ec_dev->group);
> >
> >         return 0;
> >  }
> > diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> > index 02599687770c5..c6dca260bbd5d 100644
> > --- a/include/linux/platform_data/cros_ec_proto.h
> > +++ b/include/linux/platform_data/cros_ec_proto.h
> > @@ -191,6 +191,7 @@ struct cros_ec_platform {
> >  /**
> >   * struct cros_ec_dev - ChromeOS EC device entry point.
> >   * @class_dev: Device structure used in sysfs.
> > + * @groups: sysfs attributes groups for this EC.
> >   * @ec_dev: cros_ec_device structure to talk to the physical device.
> >   * @dev: Pointer to the platform device.
> >   * @debug_info: cros_ec_debugfs structure for debugging information.
> > @@ -200,6 +201,7 @@ struct cros_ec_platform {
> >   */
> >  struct cros_ec_dev {
> >         struct device class_dev;
> > +       const struct attribute_group *group;
> >         struct cros_ec_device *ec_dev;
> >         struct device *dev;
> >         struct cros_ec_debugfs *debug_info;
> > --
> > 2.32.0.554.ge1b32706d8-goog
> >

Re: [PATCH v3 1/1] platform/chrome: Poke kb_wake_angle attribute visibility when needed

[Tzung-Bi Shih]

On Wed, Nov 16, 2022 at 10:23:38AM -0800, Gwendal Grignou wrote:
> [+chrome-platform@lists.linux.dev]

Please also Cc to the mailing list if the patch gets chance to have
next version.

> On Mon, Nov 14, 2022 at 8:10 PM Gwendal Grignou <gwendal@chromium.org> wrote:
[...]
> > > Expose the attribute group to alter to close a potiential race between
> > > cros-ec-sensorhub and cros-ec-sysfs (that creates the attribute group
> > > on behalf of the class driver).

I failed to realize the potential race.  Could you explain it a bit?

> > > diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> > > index 02599687770c5..c6dca260bbd5d 100644
> > > --- a/include/linux/platform_data/cros_ec_proto.h
> > > +++ b/include/linux/platform_data/cros_ec_proto.h
> > > @@ -191,6 +191,7 @@ struct cros_ec_platform {
> > >  /**
> > >   * struct cros_ec_dev - ChromeOS EC device entry point.
> > >   * @class_dev: Device structure used in sysfs.
> > > + * @groups: sysfs attributes groups for this EC.

The field name has extra "s".

Re: [PATCH v3 1/1] platform/chrome: Poke kb_wake_angle attribute visibility when needed

[Gwendal Grignou]

On Thu, Nov 17, 2022 at 6:01 PM Tzung-Bi Shih <tzungbi@kernel.org> wrote:
>
> On Wed, Nov 16, 2022 at 10:23:38AM -0800, Gwendal Grignou wrote:
> > [+chrome-platform@lists.linux.dev]
>
> Please also Cc to the mailing list if the patch gets chance to have
> next version.
>
> > On Mon, Nov 14, 2022 at 8:10 PM Gwendal Grignou <gwendal@chromium.org> wrote:
> [...]
> > > > Expose the attribute group to alter to close a potiential race between
> > > > cros-ec-sensorhub and cros-ec-sysfs (that creates the attribute group
> > > > on behalf of the class driver).
>
> I failed to realize the potential race.  Could you explain it a bit?
The decision to show or not an attribute is done at the attribute file
creation time, once. If the module cros_ec_sysfs is loaded before
cros_ec_sensorhub, the attribute kb_wake_angle will never be shown. If
it is loaded after, and there are 2 accelerometers, the is_visible()
function will return true and the attribute is shown.

This patch ensures the attribute is_visible() is run again after the
sensorhub driver is loaded.

Gwendal.
>
> > > > diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> > > > index 02599687770c5..c6dca260bbd5d 100644
> > > > --- a/include/linux/platform_data/cros_ec_proto.h
> > > > +++ b/include/linux/platform_data/cros_ec_proto.h
> > > > @@ -191,6 +191,7 @@ struct cros_ec_platform {
> > > >  /**
> > > >   * struct cros_ec_dev - ChromeOS EC device entry point.
> > > >   * @class_dev: Device structure used in sysfs.
> > > > + * @groups: sysfs attributes groups for this EC.
>
> The field name has extra "s".

Re: [PATCH v3 1/1] platform/chrome: Poke kb_wake_angle attribute visibility when needed

[Tzung-Bi Shih]

On Thu, Nov 17, 2022 at 10:41:06PM -0800, Gwendal Grignou wrote:
> On Thu, Nov 17, 2022 at 6:01 PM Tzung-Bi Shih <tzungbi@kernel.org> wrote:
> >
> > On Wed, Nov 16, 2022 at 10:23:38AM -0800, Gwendal Grignou wrote:
> > > [+chrome-platform@lists.linux.dev]
> >
> > Please also Cc to the mailing list if the patch gets chance to have
> > next version.
> >
> > > On Mon, Nov 14, 2022 at 8:10 PM Gwendal Grignou <gwendal@chromium.org> wrote:
> > [...]
> > > > > Expose the attribute group to alter to close a potiential race between
> > > > > cros-ec-sensorhub and cros-ec-sysfs (that creates the attribute group
> > > > > on behalf of the class driver).
> >
> > I failed to realize the potential race.  Could you explain it a bit?
> The decision to show or not an attribute is done at the attribute file
> creation time, once. If the module cros_ec_sysfs is loaded before
> cros_ec_sensorhub, the attribute kb_wake_angle will never be shown. If
> it is loaded after, and there are 2 accelerometers, the is_visible()
> function will return true and the attribute is shown.
> 
> This patch ensures the attribute is_visible() is run again after the
> sensorhub driver is loaded.

I see.  Thanks.