linux-kernel - Re: [PATCH 2/3] media: omap3isp: ispvideo: drop driver specific isp_video

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Date:	Tue, 24 Feb 2015 11:07:53 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	"Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	LMML <linux-media@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] media: omap3isp: ispvideo: drop driver specific isp_video_fh

Hi Prabhakar,

On Tuesday 24 February 2015 08:04:40 Lad, Prabhakar wrote:
> On Tue, Feb 24, 2015 at 12:35 AM, Laurent Pinchart wrote:
> > On Monday 23 February 2015 20:19:32 Lad Prabhakar wrote:
> >> From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
> >> 
> >> this patch drops driver specific isp_video_fh, as this
> >> can be handled by core.
> > 
> > I'm afraid it's not that simple.
> > 
> > The omap3isp driver stores video queues per file handle for a reason. This
> > was design to permit creating a high-resolution still image capture queue
> > and prepare buffers ahead of time, to avoid the large delay due to cache
> > management as prepare time when taking the snapshot.
> 
> Ah I see the reason.
> 
> > Now this use case has been partially solved by VIDIOC_CREATE_BUFS, but
> > we're still missing a VIDIOC_DESTROY_BUFS to make it work completely.
> > That needs to be solved first.
> 
> I haven't used the VIDIOC_CREATE_BUFS ioctl so far in any of the apps
> so cant comment much on this.
> But isn't that obvious we need VIDIOC_DESTROY_BUFS or is there any backdoor
> to destroy them that I am missing ?

You can destroy buffers allocated with CREATE_BUFS using REQBUFS(0), but you 
can't destroy them individually without a new ioctl.

> >> Signed-off-by: Lad, Prabhakar <prabhakar.csengg@...il.com>
> >> ---
> >> 
> >>  drivers/media/platform/omap3isp/ispvideo.c | 128 +++++++++--------------
> >>  drivers/media/platform/omap3isp/ispvideo.h |  13 +--
> >>  2 files changed, 49 http://vger.kernel.org/majordomo-info.html

-- 
Regards,

Laurent Pinchart

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