linux-kernel - Re: [PATCH v3 7/9] media: subdev: Support privacy led in v4l2_subdev_enable/disable

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Date: Tue, 16 Apr 2024 13:34:22 +0300
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
 Hans Verkuil <hverkuil@...all.nl>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>,
 Umang Jain <umang.jain@...asonboard.com>, linux-media@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 7/9] media: subdev: Support privacy led in
 v4l2_subdev_enable/disable_streams()

On 12/04/2024 21:20, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Wed, Apr 10, 2024 at 03:35:54PM +0300, Tomi Valkeinen wrote:
>> We support camera privacy leds with the .s_stream, in call_s_stream, but
> 
> s/the .s_stream/the .s_stream() operation/
> 
>> we don't have that support when the subdevice implements
>> .enable/disable_streams.
>>
>> Add the support by enabling the led when the first stream for a
>> subdevice is enabled, and disabling the led then the last stream is
>> disabled.
> 
> I wonder if that will always be the correct constraint for all devices,
> but I suppose we can worry about it later.
> 
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
>> ---
>>   drivers/media/v4l2-core/v4l2-subdev.c | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
>> index 20b5a00cbeeb..f44aaa4e1fab 100644
>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>> @@ -2150,6 +2150,7 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
>>   {
>>   	struct device *dev = sd->entity.graph_obj.mdev->dev;
>>   	struct v4l2_subdev_state *state;
>> +	bool already_streaming;
>>   	u64 found_streams = 0;
>>   	unsigned int i;
>>   	int ret;
>> @@ -2198,6 +2199,8 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
>>   
>>   	dev_dbg(dev, "enable streams %u:%#llx\n", pad, streams_mask);
>>   
>> +	already_streaming = v4l2_subdev_is_streaming(sd);
>> +
>>   	/* Call the .enable_streams() operation. */
>>   	ret = v4l2_subdev_call(sd, pad, enable_streams, state, pad,
>>   			       streams_mask);
>> @@ -2216,6 +2219,9 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
>>   			cfg->enabled = true;
>>   	}
>>   
>> +	if (!already_streaming)
>> +		v4l2_subdev_enable_privacy_led(sd);
>> +
>>   done:
>>   	v4l2_subdev_unlock_state(state);
>>   
>> @@ -2340,6 +2346,9 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
>>   	}
>>   
>>   done:
>> +	if (!v4l2_subdev_is_streaming(sd))
> 
> Wouldn't it be more efficient to check this while looping over the
> stream configs in the loop just above ? Same for
> v4l2_subdev_enable_streams().

It would, but it would get a lot messier to manage with "media: subdev: 
Refactor v4l2_subdev_enable/disable_streams()", and we would also need 
to support the non-routing case.

This is usually a loop with a couple of iterations, and only called when 
enabling or enabling a subdevice, so I'm not really worried about the 
performance. If it's an issue, it would probably be better to also 
update the sd->enabled_pads when enabling/disabling a stream.

  Tomi