linux-kernel - Re: [PATCH] Revert "media: uvcvideo: Remove nodrop parameter"

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Message-ID: <20260113133412.GE6198@pendragon.ideasonboard.com>
Date: Tue, 13 Jan 2026 15:34:12 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Ricardo Ribalda <ribalda@...omium.org>
Cc: Hans de Goede <hansg@...nel.org>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ralf Jung <post@...fj.de>
Subject: Re: [PATCH] Revert "media: uvcvideo: Remove nodrop parameter"

On Tue, Jan 13, 2026 at 01:29:46PM +0000, Ricardo Ribalda wrote:
> This reverts commit 27ccc44a511b0cd76dc607e2a4893b876192ee1b.
> 
> A user has reported that the Zoom Video Conferencing tool is not capable
> of handling invalid frames. Due to this, he has to continue using this
> parameter.
> 
> We will keep working with Zoom so they can handle invalid frames
> correctly, but for this cycle the safest option is to revert this
> parameter drop.

Zoom is unlikely to be the only affected application.

> Fixes: 27ccc44a511b ("media: uvcvideo: Remove nodrop parameter")
> Reported-by: Ralf Jung <post@...fj.de>
> Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1121718
> Closes: https://lore.kernel.org/linux-media/uboug5ectzm4s32yfgopjbcxq2uhsoc4kluaby7a4b7nzfjave@boco7oocnftr/
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

Hans, Mauro, can you pick this up ? Alternatively I can prepare a pull
request.

> ---
>  drivers/media/usb/uvc/uvc_driver.c | 19 +++++++++++++++++++
>  drivers/media/usb/uvc/uvc_queue.c  | 25 +++++++++++++++++++++++++
>  drivers/media/usb/uvc/uvcvideo.h   |  1 +
>  3 files changed, 45 insertions(+)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index 71563d8f4bcf581694ccd4b665ff52b629caa0b6..ee4f54d6834962414979a046afc59c5036455124 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -32,6 +32,7 @@
>  
>  unsigned int uvc_clock_param = CLOCK_MONOTONIC;
>  unsigned int uvc_hw_timestamps_param;
> +unsigned int uvc_no_drop_param = 1;
>  static unsigned int uvc_quirks_param = -1;
>  unsigned int uvc_dbg_param;
>  unsigned int uvc_timeout_param = UVC_CTRL_STREAMING_TIMEOUT;
> @@ -2467,6 +2468,24 @@ MODULE_PARM_DESC(clock, "Video buffers timestamp clock");
>  module_param_named(hwtimestamps, uvc_hw_timestamps_param, uint, 0644);
>  MODULE_PARM_DESC(hwtimestamps, "Use hardware timestamps");
>  
> +static int param_set_nodrop(const char *val, const struct kernel_param *kp)
> +{
> +	pr_warn_once("uvcvideo: "
> +		     DEPRECATED
> +		     "nodrop parameter will be eventually removed.\n");
> +	return param_set_bool(val, kp);
> +}
> +
> +static const struct kernel_param_ops param_ops_nodrop = {
> +	.set = param_set_nodrop,
> +	.get = param_get_uint,
> +};
> +
> +param_check_uint(nodrop, &uvc_no_drop_param);
> +module_param_cb(nodrop, &param_ops_nodrop, &uvc_no_drop_param, 0644);
> +__MODULE_PARM_TYPE(nodrop, "uint");
> +MODULE_PARM_DESC(nodrop, "Don't drop incomplete frames");
> +
>  module_param_named(quirks, uvc_quirks_param, uint, 0644);
>  MODULE_PARM_DESC(quirks, "Forced device quirks");
>  module_param_named(trace, uvc_dbg_param, uint, 0644);
> diff --git a/drivers/media/usb/uvc/uvc_queue.c b/drivers/media/usb/uvc/uvc_queue.c
> index 3bc54456b4d98ed50b1ea250ce8501e67141e1ef..681a74ed09fb1f109d2b21bf490e8b26eeec0a3e 100644
> --- a/drivers/media/usb/uvc/uvc_queue.c
> +++ b/drivers/media/usb/uvc/uvc_queue.c
> @@ -331,9 +331,34 @@ struct uvc_buffer *uvc_queue_get_current_buffer(struct uvc_video_queue *queue)
>  	return nextbuf;
>  }
>  
> +/*
> + * uvc_queue_buffer_requeue: Requeue a buffer on our internal irqqueue
> + *
> + * Reuse a buffer through our internal queue without the need to 'prepare'.
> + * The buffer will be returned to userspace through the uvc_buffer_queue call if
> + * the device has been disconnected.
> + */
> +static void uvc_queue_buffer_requeue(struct uvc_video_queue *queue,
> +				     struct uvc_buffer *buf)
> +{
> +	buf->error = 0;
> +	buf->state = UVC_BUF_STATE_QUEUED;
> +	buf->bytesused = 0;
> +	vb2_set_plane_payload(&buf->buf.vb2_buf, 0, 0);
> +
> +	uvc_buffer_queue(&buf->buf.vb2_buf);
> +}
> +
>  static void uvc_queue_buffer_complete(struct kref *ref)
>  {
>  	struct uvc_buffer *buf = container_of(ref, struct uvc_buffer, ref);
> +	struct vb2_buffer *vb = &buf->buf.vb2_buf;
> +	struct uvc_video_queue *queue = vb2_get_drv_priv(vb->vb2_queue);
> +
> +	if (buf->error && !uvc_no_drop_param) {
> +		uvc_queue_buffer_requeue(queue, buf);
> +		return;
> +	}
>  
>  	buf->state = buf->error ? UVC_BUF_STATE_ERROR : UVC_BUF_STATE_DONE;
>  	vb2_set_plane_payload(&buf->buf.vb2_buf, 0, buf->bytesused);
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index 911016047687f7c74fa1bf0dd0ecf2d072361346..d583425893a5f716185153a07aae9bfe20182964 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -659,6 +659,7 @@ static inline struct uvc_fh *to_uvc_fh(struct file *filp)
>  #define UVC_WARN_XU_GET_RES	2
>  
>  extern unsigned int uvc_clock_param;
> +extern unsigned int uvc_no_drop_param;
>  extern unsigned int uvc_dbg_param;
>  extern unsigned int uvc_timeout_param;
>  extern unsigned int uvc_hw_timestamps_param;
> 
> ---
> base-commit: 3aa9296a23ec41a8424e9a2346eea59fb6cb7d8c
> change-id: 20260113-uvc-revert-cd60dc7f16ec

-- 
Regards,

Laurent Pinchart