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

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Message-ID: <530d012b-50c3-ca03-a37e-fe62ac309e02@i2se.com>
Date:   Wed, 17 Oct 2018 12:50:53 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Dave Stevenson <dave.stevenson@...pberrypi.org>,
        Eric Anholt <eric@...olt.net>
Cc:     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>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH 0/7] staging: vc04_services: Some dead code removal

Hi,

Am 17.10.2018 um 11:55 schrieb Dave Stevenson:
> 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.

my statement about the old vc_sm based on assumption there wont be a
user of this driver.

In case the camera driver would use the new vc_sm driver, i would be
happier to see this merged in staging than in downstream.

Stefan

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