linux-kernel - Re: [PATCH v2 1/9] media: subdev: Add privacy led helpers

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Message-ID: <9c99ec26-74ad-41b4-99cd-23aac41efec6@redhat.com>
Date: Wed, 10 Apr 2024 11:27:00 +0200
From: Hans de Goede <hdegoede@...hat.com>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
 Hans Verkuil <hverkuil@...all.nl>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Umang Jain <umang.jain@...asonboard.com>, linux-media@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/9] media: subdev: Add privacy led helpers

Hi,

On 4/10/24 11:07 AM, Sakari Ailus wrote:
> Moi,
> 
> On Fri, Apr 05, 2024 at 12:14:19PM +0300, Tomi Valkeinen wrote:
>> Add helper functions to enable and disable the privacy led. This moves
>> the #if from the call site to the privacy led functions, and makes
>> adding privacy led support to v4l2_subdev_enable/disable_streams()
>> cleaner.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
>> ---
>>  drivers/media/v4l2-core/v4l2-subdev.c | 31 ++++++++++++++++++++++---------
>>  1 file changed, 22 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
>> index 4c6198c48dd6..942c7a644033 100644
>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>> @@ -148,6 +148,23 @@ static int subdev_close(struct file *file)
>>  }
>>  #endif /* CONFIG_VIDEO_V4L2_SUBDEV_API */
>>  
>> +static void v4l2_subdev_enable_privacy_led(struct v4l2_subdev *sd)
>> +{
>> +#if IS_REACHABLE(CONFIG_LEDS_CLASS)
>> +	if (!IS_ERR_OR_NULL(sd->privacy_led))
>> +		led_set_brightness(sd->privacy_led,
>> +				   sd->privacy_led->max_brightness);
>> +#endif
>> +}
>> +
>> +static void v4l2_subdev_disable_privacy_led(struct v4l2_subdev *sd)
>> +{
>> +#if IS_REACHABLE(CONFIG_LEDS_CLASS)
>> +	if (!IS_ERR_OR_NULL(sd->privacy_led))
>> +		led_set_brightness(sd->privacy_led, 0);
>> +#endif
>> +}
>> +
>>  static inline int check_which(u32 which)
>>  {
>>  	if (which != V4L2_SUBDEV_FORMAT_TRY &&
>> @@ -412,15 +429,11 @@ static int call_s_stream(struct v4l2_subdev *sd, int enable)
>>  	if (WARN_ON(!!sd->enabled_streams == !!enable))
>>  		return 0;
>>  
>> -#if IS_REACHABLE(CONFIG_LEDS_CLASS)
>> -	if (!IS_ERR_OR_NULL(sd->privacy_led)) {
>> -		if (enable)
>> -			led_set_brightness(sd->privacy_led,
>> -					   sd->privacy_led->max_brightness);
>> -		else
>> -			led_set_brightness(sd->privacy_led, 0);
>> -	}
>> -#endif
>> +	if (enable)
>> +		v4l2_subdev_enable_privacy_led(sd);
>> +	else
>> +		v4l2_subdev_disable_privacy_led(sd);
>> +
>>  	ret = sd->ops->video->s_stream(sd, enable);
> 
> I see that you're only making changes before the s_stream call which also
> reveals a bug here: if streaming on fails, the LED will remain lit. It
> should be fixed before this set.
> 
> I cc'd Hans de Goede.

Right that seems like a bug which I introduced. I think it would be
best to move the setting of the LED on/off to after the s_stream()
call in the:

       if (!ret)
                sd->enabled_streams = enable ? BIT(0) : 0;

block, so that the LED is not touched when s_stream(sd, 1) fails.

This delay enabling the LED slightly on stream start but IMHO
that is not a bit issue.

Regards,

Hans