linux-kernel - Re: [PATCH 04/11] media: cedrus: Add helper for checking capabilities

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Date:   Tue, 25 Oct 2022 17:28:22 +0200
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>, mripard@...nel.org,
        mchehab@...nel.org, gregkh@...uxfoundation.org, wens@...e.org,
        samuel@...lland.org, hverkuil-cisco@...all.nl,
        linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/11] media: cedrus: Add helper for checking capabilities

Dne torek, 25. oktober 2022 ob 17:22:59 CEST je Paul Kocialkowski napisal(a):
> Hi Jernej,
> 
> On Tue 25 Oct 22, 17:17, Jernej Škrabec wrote:
> > Dne torek, 25. oktober 2022 ob 08:30:28 CEST je Dan Carpenter napisal(a):
> > > On Mon, Oct 24, 2022 at 10:15:08PM +0200, Jernej Skrabec wrote:
> > > > There is several different Cedrus cores with varying capabilities, so
> > > > some operations like listing formats depends on checks if feature is
> > > > supported or not.
> > > > 
> > > > Currently check for capabilities is only in format enumeration helper,
> > > > but it will be used also elsewhere later. Let's convert this check to
> > > > helper and while at it, also simplify it. There is no need to check if
> > > > capability mask is zero, condition will still work properly.
> > > 
> > > Sure.  That's true.  Out of curiousity, can
> > > cedrus_formats[i].capabilities
> > > be zero?  Because it feels like that's what should be checked.
> > 
> > Yes, it can be. It's the case for V4L2_PIX_FMT_NV12_32L32. All variants
> > supports it, so there is no special capability needed in order to be
> > listed. What would you check in such case? Condition still works for this
> > case.
> I think the problem is that (bits & 0) == 0 is always true.
> So if the input caps are 0, we need to make sure to return false.

No. If format (or any other) capabilities are 0, means they are supported by 
all variants and it's expected from cedrus_is_capable() to return true.

Regards,
Jernej