linux-kernel - Re: [PATCH v5 02/12] media: uvcvideo: Allow more that one asyc

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Date:   Tue, 22 Dec 2020 10:07:55 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 02/12] media: uvcvideo: Allow more that one asyc_ctrl

Hi Ricardo,

Thank you for the patch.

On Mon, Dec 21, 2020 at 05:48:09PM +0100, Ricardo Ribalda wrote:
> The current implementation allocates memory for only one async_control.
> If we get a second event before we have processed the previous one, the
> old one gets lost.
> 
> Introduce a dynamic memory allocation and a list to handle the
> async_controls.

Thinking some more about this, do we need to go through the work queue
at all for GPIO-based events ? Could the part of
uvc_ctrl_status_event_work() before the URB resubmission be moved to
another function, which would be called directly by the GPIO threaded
IRQ handler ?

> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 49 ++++++++++++++++++++++++++------
>  drivers/media/usb/uvc/uvcvideo.h | 19 ++++++++-----
>  2 files changed, 52 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index aa18dcdf8165..69b2fc6ce12c 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1275,11 +1275,9 @@ static void uvc_ctrl_send_slave_event(struct uvc_video_chain *chain,
>  	uvc_ctrl_send_event(chain, handle, ctrl, mapping, val, changes);
>  }
>  
> -static void uvc_ctrl_status_event_work(struct work_struct *work)
> +static void __uvc_ctrl_status_event_work(struct uvc_device *dev,
> +					 struct uvc_ctrl_work *w)
>  {
> -	struct uvc_device *dev = container_of(work, struct uvc_device,
> -					      async_ctrl.work);
> -	struct uvc_ctrl_work *w = &dev->async_ctrl;
>  	struct uvc_video_chain *chain = w->chain;
>  	struct uvc_control_mapping *mapping;
>  	struct uvc_control *ctrl = w->ctrl;
> @@ -1321,23 +1319,54 @@ static void uvc_ctrl_status_event_work(struct work_struct *work)
>  			   ret);
>  }
>  
> +static void uvc_ctrl_status_event_work(struct work_struct *work)
> +{
> +	struct uvc_device *dev = container_of(work, struct uvc_device,
> +					      async_ctrl_work);
> +	struct uvc_ctrl_work *w;
> +
> +	do {
> +		mutex_lock(&dev->async_ctrl_lock);
> +		w = list_first_entry_or_null(&dev->async_ctrl_list,
> +					     struct uvc_ctrl_work,
> +					     list);
> +		if (w)
> +			list_del(&w->list);
> +		mutex_unlock(&dev->async_ctrl_lock);
> +
> +		if (!w)
> +			return;
> +
> +		__uvc_ctrl_status_event_work(dev, w);
> +		kfree(w);
> +	} while (w);
> +}
> +
>  bool uvc_ctrl_status_event(struct urb *urb, struct uvc_video_chain *chain,
>  			   struct uvc_control *ctrl, const u8 *data)
>  {
>  	struct uvc_device *dev = chain->dev;
> -	struct uvc_ctrl_work *w = &dev->async_ctrl;
> +	struct uvc_ctrl_work *w;
>  
>  	if (list_empty(&ctrl->info.mappings)) {
>  		ctrl->handle = NULL;
>  		return false;
>  	}
>  
> +	w = kzalloc(sizeof(*w), GFP_KERNEL);
> +	if (WARN(!w, "Not enough memory to trigger uvc event"))
> +		return false;
> +
>  	memcpy(w->data, data, ctrl->info.size);
>  	w->urb = urb;
>  	w->chain = chain;
>  	w->ctrl = ctrl;
>  
> -	schedule_work(&w->work);
> +	mutex_lock(&dev->async_ctrl_lock);
> +	list_add_tail(&w->list, &dev->async_ctrl_list);
> +	mutex_unlock(&dev->async_ctrl_lock);
> +
> +	schedule_work(&dev->async_ctrl_work);
>  
>  	return true;
>  }
> @@ -2277,7 +2306,9 @@ int uvc_ctrl_init_device(struct uvc_device *dev)
>  	struct uvc_entity *entity;
>  	unsigned int i;
>  
> -	INIT_WORK(&dev->async_ctrl.work, uvc_ctrl_status_event_work);
> +	INIT_WORK(&dev->async_ctrl_work, uvc_ctrl_status_event_work);
> +	mutex_init(&dev->async_ctrl_lock);
> +	INIT_LIST_HEAD(&dev->async_ctrl_list);
>  
>  	/* Walk the entities list and instantiate controls */
>  	list_for_each_entry(entity, &dev->entities, list) {
> @@ -2348,8 +2379,8 @@ void uvc_ctrl_cleanup_device(struct uvc_device *dev)
>  	unsigned int i;
>  
>  	/* Can be uninitialized if we are aborting on probe error. */
> -	if (dev->async_ctrl.work.func)
> -		cancel_work_sync(&dev->async_ctrl.work);
> +	if (dev->async_ctrl_work.func)
> +		cancel_work_sync(&dev->async_ctrl_work);
>  
>  	/* Free controls and control mappings for all entities. */
>  	list_for_each_entry(entity, &dev->entities, list) {
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index 0db6c2e0bd98..afcaf49fad1a 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -637,6 +637,14 @@ struct uvc_device_info {
>  	u32	meta_format;
>  };
>  
> +struct uvc_ctrl_work {
> +	struct list_head list;
> +	struct urb *urb;
> +	struct uvc_video_chain *chain;
> +	struct uvc_control *ctrl;
> +	u8 data[UVC_MAX_STATUS_SIZE];
> +};
> +
>  struct uvc_device {
>  	struct usb_device *udev;
>  	struct usb_interface *intf;
> @@ -673,13 +681,10 @@ struct uvc_device {
>  	struct input_dev *input;
>  	char input_phys[64];
>  
> -	struct uvc_ctrl_work {
> -		struct work_struct work;
> -		struct urb *urb;
> -		struct uvc_video_chain *chain;
> -		struct uvc_control *ctrl;
> -		u8 data[UVC_MAX_STATUS_SIZE];
> -	} async_ctrl;
> +	/* Async control */
> +	struct work_struct async_ctrl_work;
> +	struct list_head async_ctrl_list;
> +	struct mutex async_ctrl_lock;
>  };
>  
>  enum uvc_handle_state {

-- 
Regards,

Laurent Pinchart