linux-kernel - Re: [PATCHv3 02/11] videobuf2: handle V4L2 buffer cache flags

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Message-ID: <20200228012042.GK122464@google.com>
Date:   Fri, 28 Feb 2020 10:20:42 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Sakari Ailus <sakari.ailus@....fi>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Pawel Osciak <posciak@...omium.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 02/11] videobuf2: handle V4L2 buffer cache flags

On (20/02/27 12:58), Hans Verkuil wrote:
[..]
> > There are two possible alternative approaches:
> > - The first one is to move cache sync from ->finish() to dqbuf().
> >   But this breaks some drivers, that need to fix-up buffers before
> >   dequeueing them.
> > 
> > - The second one is to move ->finish() call from ->done() to dqbuf.
> 
> It's not clear what the purpose is of describing these alternative approaches.
> I'd just drop that. It's a bit confusing.

OK.

> > +/**
> > + * vb2_queue_allows_cache_hints() - Return true if the queue allows cache
> > + * and memory consistency hints.
> > + *
> > + * @q:		pointer to &struct vb2_queue with videobuf2 queue
> > + */
> > +static inline bool vb2_queue_allows_cache_hints(struct vb2_queue *q)
> > +{
> > +	return (q->allow_cache_hints != 0) && (q->memory == VB2_MEMORY_MMAP);
> 
> Simply to:
> 
> 	return q->allow_cache_hints && q->memory == VB2_MEMORY_MMAP;
> 

OK. I saw vb2_is_busy()

static inline bool vb2_is_busy(struct vb2_queue *q)
{
	return (q->num_buffers > 0);
}

in the very same header file and concluded that maybe this is the
preferred style.

	-ss