linux-kernel - Re: [PATCH] platform/chrome: Update cros_ec sysfs attributes on sensors discovery

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Date:   Sat, 3 Apr 2021 09:52:46 +0200
From:   Greg KH <greg@...ah.com>
To:     Gwendal Grignou <gwendal@...omium.org>
Cc:     bleung@...omium.org, enric.balletbo@...labora.com,
        groeck@...omium.org, linux-kernel@...r.kernel.org,
        Gwendal Grignou <gwendal@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH] platform/chrome: Update cros_ec sysfs attributes on
 sensors discovery

On Fri, Apr 02, 2021 at 11:20:31PM -0700, Gwendal Grignou wrote:
> When cros_ec_sysfs probe is called before cros_ec_sensorhub probe
> routine, the |kb_wake_angle| attribute will not be displayed, even if
> there are two accelerometers in the chromebook.
> 
> Call sysfs_update_group() when accelerometers are enumerated if the
> cros_ec sysfs attributes group has already been created.
> 
> Fixes: d60ac88a62df ("mfd / platform / iio: cros_ec: Register sensor through sensorhub")
> Cc: stable@...r.kernel.org
> Signed-off-by: Gwendal Grignou <gwendal@...gle.com>
> ---
>  drivers/platform/chrome/cros_ec_sensorhub.c | 5 ++++-
>  drivers/platform/chrome/cros_ec_sysfs.c     | 2 ++
>  include/linux/platform_data/cros_ec_proto.h | 2 ++
>  3 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/chrome/cros_ec_sensorhub.c b/drivers/platform/chrome/cros_ec_sensorhub.c
> index 9c4af76a9956e..78085ad362ca8 100644
> --- a/drivers/platform/chrome/cros_ec_sensorhub.c
> +++ b/drivers/platform/chrome/cros_ec_sensorhub.c
> @@ -106,8 +106,11 @@ 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);
> +	}
>  
>  	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..3838d5f51aadc 100644
> --- a/drivers/platform/chrome/cros_ec_sysfs.c
> +++ b/drivers/platform/chrome/cros_ec_sysfs.c
> @@ -344,6 +344,8 @@ static int cros_ec_sysfs_probe(struct platform_device *pd)
>  	ret = sysfs_create_group(&ec_dev->class_dev.kobj, &cros_ec_attr_group);

This is odd, the platform/driver core should be creating these files,
you should never have to do this "by hand".  If you do it this way, you
are racing with userspace and loosing.

Please set the dev_groups field in the driver structure to be this group
and then all will be fine automatically.

>  	if (ret < 0)
>  		dev_err(dev, "failed to create attributes. err=%d\n", ret);
> +	else
> +		ec_dev->group = &cros_ec_attr_group;
>  
>  	return ret;
>  }
> diff --git a/include/linux/platform_data/cros_ec_proto.h b/include/linux/platform_data/cros_ec_proto.h
> index 02599687770c5..4cd06f68bc536 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.
> + * @group: sysfs attributes group 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;
> +	struct attribute_group *group;

This should not be needed.

thanks,

greg k-h