Re: [PATCH v3 06/11] v4l: subdev: Make the v4l2-subdev core code enable/disable the privacy LED if present

[Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>]

Hi Hans,

Thank you for the patch.

On Fri, Dec 16, 2022 at 12:30:08PM +0100, Hans de Goede wrote:
> Extend the call_s_stream() wrapper to enable/disable sensor privacy LEDs
> for sensors with a privacy LED, rather then having to duplicate this code
> in all the sensor drivers.
> 
> Suggested-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 40 +++++++++++++++++++++++++++
>  include/media/v4l2-subdev.h           |  3 ++
>  2 files changed, 43 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 4988a25bd8f4..7344f6cd58b7 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -318,10 +318,44 @@ static int call_get_mbus_config(struct v4l2_subdev *sd, unsigned int pad,
>  	       sd->ops->pad->get_mbus_config(sd, pad, config);
>  }
>  
> +#if IS_REACHABLE(CONFIG_LEDS_CLASS)
> +#include <linux/leds.h>

Can this be moved to the top of the file ? It doesn't have to be
conditionally compiled there.

> +
> +static void call_s_stream_update_pled(struct v4l2_subdev *sd, int enable)
> +{
> +	if (!sd->dev)
> +		return;
> +
> +	/* Try to get privacy-led once, at first s_stream() */
> +	if (!sd->privacy_led)
> +		sd->privacy_led = led_get(sd->dev, "privacy-led");

I'm not sure I like this much. If the LED provider isn't available
(yet), the LED will stay off. That's a privacy concern.

> +
> +	if (IS_ERR(sd->privacy_led))
> +		return;
> +
> +	mutex_lock(&sd->privacy_led->led_access);
> +
> +	if (enable) {
> +		led_sysfs_disable(sd->privacy_led);
> +		led_trigger_remove(sd->privacy_led);
> +		led_set_brightness(sd->privacy_led, sd->privacy_led->max_brightness);
> +	} else {
> +		led_set_brightness(sd->privacy_led, 0);
> +		led_sysfs_enable(sd->privacy_led);

I don't think you should reenable control through sysfs here. I don't
really see a use case, and you've removed the trigger anyway, so the
behaviour would be quite inconsistent.

> +	}
> +
> +	mutex_unlock(&sd->privacy_led->led_access);
> +}
> +#else
> +static void call_s_stream_update_pled(struct v4l2_subdev *sd, int enable) {}
> +#endif
> +
>  static int call_s_stream(struct v4l2_subdev *sd, int enable)
>  {
>  	int ret;
>  
> +	call_s_stream_update_pled(sd, enable);
> +
>  	ret = sd->ops->video->s_stream(sd, enable);
>  
>  	if (!enable && ret < 0) {

You need to turn the LED off when enabling if .s_stream() fails.

> @@ -1050,6 +1084,11 @@ EXPORT_SYMBOL_GPL(__v4l2_subdev_init_finalize);
>  
>  void v4l2_subdev_cleanup(struct v4l2_subdev *sd)
>  {
> +#if IS_REACHABLE(CONFIG_LEDS_CLASS)
> +	if (!IS_ERR_OR_NULL(sd->privacy_led))
> +		led_put(sd->privacy_led);
> +#endif
> +
>  	__v4l2_subdev_state_free(sd->active_state);
>  	sd->active_state = NULL;
>  }
> @@ -1090,6 +1129,7 @@ void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)
>  	sd->grp_id = 0;
>  	sd->dev_priv = NULL;
>  	sd->host_priv = NULL;
> +	sd->privacy_led = NULL;
>  #if defined(CONFIG_MEDIA_CONTROLLER)
>  	sd->entity.name = sd->name;
>  	sd->entity.obj_type = MEDIA_ENTITY_TYPE_V4L2_SUBDEV;
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index b15fa9930f30..0547313f98cc 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -38,6 +38,7 @@ struct v4l2_subdev;
>  struct v4l2_subdev_fh;
>  struct tuner_setup;
>  struct v4l2_mbus_frame_desc;
> +struct led_classdev;
>  
>  /**
>   * struct v4l2_decode_vbi_line - used to decode_vbi_line
> @@ -982,6 +983,8 @@ struct v4l2_subdev {
>  	 * appropriate functions.
>  	 */
>  
> +	struct led_classdev *privacy_led;
> +
>  	/*
>  	 * TODO: active_state should most likely be changed from a pointer to an
>  	 * embedded field. For the time being it's kept as a pointer to more

-- 
Regards,

Laurent Pinchart