linux-kernel - Re: [PATCH v2 02/10] media-request: Add a request complete operation to allow m2m scheduling

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Date:   Fri, 04 May 2018 10:03:05 +0200
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>, Pawel Osciak <pawel@...iak.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Arnd Bergmann <arnd@...db.de>,
        Alexandre Courbot <acourbot@...omium.org>,
        Tomasz Figa <tfiga@...omium.org>
Subject: Re: [PATCH v2 02/10] media-request: Add a request complete
 operation to allow m2m scheduling

Hi,

On Thu, 2018-04-19 at 17:41 +0200, Paul Kocialkowski wrote:
> When using the request API in the context of a m2m driver, the
> operations that come with a m2m run scheduling call in their
> (m2m-specific) ioctl handler are delayed until the request is queued
> (for instance, this includes queuing buffers and streamon).
> 
> Thus, the m2m run scheduling calls are not called in due time since
> the
> request AP's internal plumbing will (rightfully) use the relevant core
> functions directly instead of the ioctl handler.
> 
> This ends up in a situation where nothing happens if there is no
> run-scheduling ioctl called after queuing the request.
> 
> In order to circumvent the issue, a new media operation is introduced,
> called at the time of handling the media request queue ioctl. It gives
> m2m drivers a chance to schedule a m2m device run at that time.
> 
> The existing req_queue operation cannot be used for this purpose,
> since
> it is called with the request queue mutex held, that is eventually
> needed
> in the device_run call to apply relevant controls.

This patch will be dropped since it's no longer useful with the latest
version of the request API.

> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> ---
>  drivers/media/media-request.c | 3 +++
>  include/media/media-device.h  | 2 ++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/media/media-request.c b/drivers/media/media-
> request.c
> index 415f7e31019d..28ac5ccfe6a2 100644
> --- a/drivers/media/media-request.c
> +++ b/drivers/media/media-request.c
> @@ -157,6 +157,9 @@ static long media_request_ioctl_queue(struct
> media_request *req)
>  		media_request_get(req);
>  	}
>  
> +	if (mdev->ops->req_complete)
> +		mdev->ops->req_complete(req);
> +
>  	return ret;
>  }
>  
> diff --git a/include/media/media-device.h b/include/media/media-
> device.h
> index 07e323c57202..c7dcf2079cc9 100644
> --- a/include/media/media-device.h
> +++ b/include/media/media-device.h
> @@ -55,6 +55,7 @@ struct media_entity_notify {
>   * @req_alloc: Allocate a request
>   * @req_free: Free a request
>   * @req_queue: Queue a request
> + * @req_complete: Complete a request
>   */
>  struct media_device_ops {
>  	int (*link_notify)(struct media_link *link, u32 flags,
> @@ -62,6 +63,7 @@ struct media_device_ops {
>  	struct media_request *(*req_alloc)(struct media_device
> *mdev);
>  	void (*req_free)(struct media_request *req);
>  	int (*req_queue)(struct media_request *req);
> +	void (*req_complete)(struct media_request *req);
>  };
>  
>  /**
-- 
Paul Kocialkowski, Bootlin (formerly Free Electrons)
Embedded Linux and kernel engineering
https://bootlin.com
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