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

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Date:   Wed, 17 Oct 2018 17:51:11 +0100
From:   Peter Robinson <pbrobinson@...il.com>
To:     eric@...olt.net
Cc:     dan.carpenter@...cle.com, stefan.wahren@...e.com,
        devel@...verdev.osuosl.org, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, tuomas.tynkkynen@....fi,
        linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/7] staging: vc04_services: Some dead code removal

> >> > 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.

I think that makes sense as long as the firmware side changes are in
place so it can actually be used.

Peter