linux-kernel - Re: [PATCH 0/7] staging: vc04_services: Some dead code removal

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Message-ID: <87bm7stwhv.fsf@anholt.net>
Date:   Wed, 17 Oct 2018 08:37:32 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Stefan Wahren <stefan.wahren@...e.com>
Cc:     Tuomas Tynkkynen <tuomas.tynkkynen@....fi>, phil@...pberrypi.org,
        devel@...verdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/7] staging: vc04_services: Some dead code removal

Dan Carpenter <dan.carpenter@...cle.com> writes:

> On Sat, Oct 06, 2018 at 12:18:38PM +0200, Stefan Wahren wrote:
>> Hi Tuomas,
>> 
>> > Tuomas Tynkkynen <tuomas.tynkkynen@....fi> hat am 4. Oktober 2018 um 11:37 geschrieben:
>> > 
>> > 
>> > Drop various pieces of dead code from here and there to get rid of
>> > the remaining users of VCHI_CONNECTION_T. After that we get to drop
>> > entire header files worth of unused code.
>> > 
>> > I've tested on a Raspberry Pi Model B (bcm2835_defconfig) that
>> > snd-bcm2835 can still play analog audio just fine.
>> > 
>> 
>> thanks and i'm fine with your patch series:
>> 
>> Acked-by: Stefan Wahren <stefan.wahren@...e.com>
>> 
>> Unfortunately this would break compilation of the downstream vchi
>> drivers like vcsm [1]. Personally i don't want to maintain another
>> one, because i cannot see the gain of the resulting effort.
>> 
>> [1] - https://github.com/raspberrypi/linux/tree/rpi-4.14.y/drivers/char/broadcom/vc_sm
>
>
> I feel like everyone else already knows the answer but why don't we just
> merge that code into staging?

Dave's been working on a new VCSM service where the firmware can call
back into Linux to allocate (instead of just having a permanent carveout
of system memory that the firmware allocates from), and lets us make
dma-bufs out of those buffers.  That driver makes a no-copies v4l2 media
decode driver possible, which would then let Kodi and similar projects
switch from downstream kernels with closed graphics to upstream kernels
with open graphics.

Given that the new VCSM service is a rewrite, it's not clear to me that
importing the old VCSM driver is a win.  But maybe we should go raid
https://github.com/6by9/linux/tree/rpi-4.14.y-codecs-push-pt2a and grab
the new drivers.  Upstreaming the VCHI audio driver to staging has
clearly been a win for it, so maybe other eyes on the new v4l2 codec
could help Dave along in stabilizing it.

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