Re: [PATCH 7/9] media: uvcvideo: uvc_v4l2_unlocked_ioctl: Invert PM logic

[Hans de Goede <hansg@kernel.org>]

Hi Ricardo,

On 28-May-25 19:58, Ricardo Ribalda wrote:
> Instead of listing the IOCTLs that do not need to turn on the camera,
> list the IOCTLs that need to turn it on. This makes the code more
> maintainable.
> 
> This patch is designed to be a NOP. Non relevant IOCTLs will be removed
> in future patches.
> 
> Suggested-by: Hans Verkuil <hans@jjverkuil.nl>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_v4l2.c | 117 +++++++++++++++++++++++++++++++--------
>  1 file changed, 93 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index 2c6f3cf6bcc3f116bbdb3383d9af7d5be9832537..e7373a2ae3c37ca02f9076773154901a603820ac 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -1264,42 +1264,111 @@ static long uvc_v4l2_compat_ioctl32(struct file *file,
>  }
>  #endif
>  
> -static long uvc_v4l2_unlocked_ioctl(struct file *file,
> -				    unsigned int cmd, unsigned long arg)
> +static long uvc_v4l2_pm_ioctl(struct file *file,
> +			      unsigned int cmd, unsigned long arg)
>  {
>  	struct uvc_fh *handle = file->private_data;
>  	int ret;
>  
> -	/* The following IOCTLs do not need to turn on the camera. */
> -	switch (cmd) {
> -	case VIDIOC_CREATE_BUFS:
> -	case VIDIOC_DQBUF:
> -	case VIDIOC_ENUM_FMT:
> -	case VIDIOC_ENUM_FRAMEINTERVALS:
> -	case VIDIOC_ENUM_FRAMESIZES:
> -	case VIDIOC_ENUMINPUT:
> -	case VIDIOC_EXPBUF:
> -	case VIDIOC_G_FMT:
> -	case VIDIOC_G_PARM:
> -	case VIDIOC_G_SELECTION:
> -	case VIDIOC_QBUF:
> -	case VIDIOC_QUERYCAP:
> -	case VIDIOC_REQBUFS:
> -	case VIDIOC_SUBSCRIBE_EVENT:
> -	case VIDIOC_UNSUBSCRIBE_EVENT:
> -		return video_ioctl2(file, cmd, arg);
> -	}
> -
>  	ret = uvc_pm_get(handle->stream->dev);
>  	if (ret)
>  		return ret;
> -
>  	ret = video_ioctl2(file, cmd, arg);
> -
>  	uvc_pm_put(handle->stream->dev);
> +
>  	return ret;
>  }
>  
> +static long uvc_v4l2_unlocked_ioctl(struct file *file,
> +				    unsigned int cmd, unsigned long arg)
> +{
> +	/*
> +	 * For now, we do not support granular power saving for compat
> +	 * syscalls.
> +	 */
> +	if (in_compat_syscall())
> +		return uvc_v4l2_pm_ioctl(file, cmd, arg);
> +
> +	/* The following IOCTLs do need to turn on the camera. */
> +	switch (cmd) {
> +	case UVCIOC_CTRL_MAP:
> +	case UVCIOC_CTRL_QUERY:
> +	case VIDIOC_CROPCAP:
> +	case VIDIOC_DBG_G_CHIP_INFO:
> +	case VIDIOC_DBG_G_REGISTER:
> +	case VIDIOC_DBG_S_REGISTER:
> +	case VIDIOC_DECODER_CMD:
> +	case VIDIOC_DQEVENT:
> +	case VIDIOC_DV_TIMINGS_CAP:
> +	case VIDIOC_ENCODER_CMD:
> +	case VIDIOC_ENUMAUDIO:
> +	case VIDIOC_ENUMAUDOUT:
> +	case VIDIOC_ENUMOUTPUT:
> +	case VIDIOC_ENUMSTD:
> +	case VIDIOC_ENUM_DV_TIMINGS:
> +	case VIDIOC_ENUM_FREQ_BANDS:
> +	case VIDIOC_G_AUDIO:
> +	case VIDIOC_G_AUDOUT:
> +	case VIDIOC_G_CROP:
> +	case VIDIOC_G_CTRL:
> +	case VIDIOC_G_DV_TIMINGS:
> +	case VIDIOC_G_EDID:
> +	case VIDIOC_G_ENC_INDEX:
> +	case VIDIOC_G_EXT_CTRLS:
> +	case VIDIOC_G_FBUF:
> +	case VIDIOC_G_FREQUENCY:
> +	case VIDIOC_G_INPUT:
> +	case VIDIOC_G_JPEGCOMP:
> +	case VIDIOC_G_MODULATOR:
> +	case VIDIOC_G_OUTPUT:
> +	case VIDIOC_G_PRIORITY:
> +	case VIDIOC_G_SLICED_VBI_CAP:
> +	case VIDIOC_G_STD:
> +	case VIDIOC_G_TUNER:
> +	case VIDIOC_LOG_STATUS:
> +	case VIDIOC_OVERLAY:
> +	case VIDIOC_PREPARE_BUF:
> +	case VIDIOC_QUERYBUF:
> +	case VIDIOC_QUERYCAP:
> +	case VIDIOC_QUERYCTRL:
> +	case VIDIOC_QUERYMENU:
> +	case VIDIOC_QUERYSTD:
> +	case VIDIOC_QUERY_DV_TIMINGS:
> +	case VIDIOC_QUERY_EXT_CTRL:
> +	case VIDIOC_REMOVE_BUFS:
> +	case VIDIOC_STREAMOFF:
> +	case VIDIOC_STREAMON:
> +	case VIDIOC_S_AUDIO:
> +	case VIDIOC_S_AUDOUT:
> +	case VIDIOC_S_CROP:
> +	case VIDIOC_S_CTRL:
> +	case VIDIOC_S_DV_TIMINGS:
> +	case VIDIOC_S_EDID:
> +	case VIDIOC_S_EXT_CTRLS:
> +	case VIDIOC_S_FBUF:
> +	case VIDIOC_S_FMT:
> +	case VIDIOC_S_FREQUENCY:
> +	case VIDIOC_S_HW_FREQ_SEEK:
> +	case VIDIOC_S_INPUT:
> +	case VIDIOC_S_JPEGCOMP:
> +	case VIDIOC_S_MODULATOR:
> +	case VIDIOC_S_OUTPUT:
> +	case VIDIOC_S_PARM:
> +	case VIDIOC_S_PRIORITY:
> +	case VIDIOC_S_SELECTION:
> +	case VIDIOC_S_STD:
> +	case VIDIOC_S_TUNER:
> +	case VIDIOC_TRY_DECODER_CMD:
> +	case VIDIOC_TRY_ENCODER_CMD:
> +	case VIDIOC_TRY_EXT_CTRLS:
> +	case VIDIOC_TRY_FMT:
> +		return uvc_v4l2_pm_ioctl(file, cmd, arg);
> +	}

IMHO adding a whole bunch of ioctls which are not supported by UVC at all here
and then dropping them again in patch 8/9 is not helpful.

I understand that your purpose is to have this initial patch
be a no-op, still doing the uvc_pm_get() + uvc_pm_put() for
unsupported IOCTLs but I don't really see that as something
useful to do while at the same time introducing unnecessary churn.

My preference would be to drop unsupported IOCTLs from this list
right away with a remark in the commit message that this changes
the behavior for unsupported IOCTLs.

For something like UVCIOC_CTRL_MAP I do agree that it is best
to keep it here and drop it later separately. Or maybe it would
be cleaner to add UVCIOC_CTRL_MAP to the list of IOCTLs _not_
needing pm before this patch ?

Regards,

Hans



> +
> +	/* The other IOCTLs can run with the camera off. */
> +	return video_ioctl2(file, cmd, arg);
> +}
> +
>  const struct v4l2_ioctl_ops uvc_ioctl_ops = {
>  	.vidioc_g_fmt_vid_cap = uvc_ioctl_g_fmt,
>  	.vidioc_g_fmt_vid_out = uvc_ioctl_g_fmt,
>