linux-kernel - Re: [PATCH v6 03/14] videobuf2: handle V4L2 buffer cache flags

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Message-ID: <20200602121049.GB617@jagdpanzerIV.localdomain>
Date:   Tue, 2 Jun 2020 21:10:49 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Tomasz Figa <tfiga@...omium.org>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH v6 03/14] videobuf2: handle V4L2 buffer cache flags

On (20/06/02 12:27), Hans Verkuil wrote:
[..]
> > Sorry, Hans, do you suggest to have something like this:
> > 
> > 	if (q->memory == VB2_MEMORY_DMABUF) {
> > 		vb->need_cache_sync_on_finish = 0;
> > 		vb->need_cache_sync_on_prepare = 0;
> > 		b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_INVALIDATE;
> > 		b->flags &= ~V4L2_BUF_FLAG_NO_CACHE_CLEAN;
> > 		return;
> > 	}
> > 
> > I didn't clear the ->flags there because we clear the vb flush/sync
> > flags: ->need_cache_sync_on_finish/prepare are zeros for DMABUF memory
> > type. Which is equivalent to passing V4L2_BUF_FLAG_NO_CACHE_INVALIDATE
> > V4L2_BUF_FLAG_NO_CACHE_CLEAN. IOW we would clearing both "vb's do cache
> > sync" and request's "do not cache sync".
> 
> Ah, yes. In that case the v4l-utils patch is likely wrong.
> Can you take a look at that patch?

Hans, are we talking about "v4l2-utils: test cache_hints for MMAP queues"
patch? I can take a look, yes.

	-ss