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

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Date:   Wed, 17 Oct 2018 10:55:06 +0100
From:   Dave Stevenson <dave.stevenson@...pberrypi.org>
To:     Eric Anholt <eric@...olt.net>
Cc:     Stefan Wahren <stefan.wahren@...e.com>, tuomas.tynkkynen@....fi,
        Phil Elwell <phil@...pberrypi.org>, devel@...verdev.osuosl.org,
        Greg KH <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>
Subject: Re: [PATCH 0/7] staging: vc04_services: Some dead code removal

On Mon, 15 Oct 2018 at 17:27, Eric Anholt <eric@...olt.net> wrote:
>
> Stefan Wahren <stefan.wahren@...e.com> writes:
>
> > 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'm happy enough to work around these changes. Once the change is in a
released kernel we can merge a modified version of vc_sm into the
downstream kernel branch. It's not as if it requires big changes.

> I think the main concern would be if we removed things necessary for
> 6by9's new vcsm (the one that will let us do dma-buf sharing between
> media decode and DRM).

The new vcsm uses the same VCHI service as the existing downstream vc_sm driver.
The video codec driver don't use any VCHI functionality over and above
the camera. It goes via a slightly extended version of the
mmal-vchiq.c, which I have split out into a shared module.

> On the other hand, git revert is a thing, so it's not like we actually
> lose anything.

:-)

  Dave