linux-kernel - Re: [PATCH v6 3/3] sound/usb: Use Media Controller API to share media resources

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Date:   Fri, 9 Dec 2016 01:44:07 +0200
From:   Sakari Ailus <sakari.ailus@....fi>
To:     Shuah Khan <shuahkh@....samsung.com>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        mchehab@...nel.org, tiwai@...e.com, perex@...ex.cz,
        hans.verkuil@...co.com, javier@....samsung.com,
        chehabrafael@...il.com, g.liakhovetski@....de, ONeukum@...e.com,
        k@...w.org, daniel@...que.org, mahasler@...il.com,
        clemens@...isch.de, geliangtang@....com, vdronov@...hat.com,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        alsa-devel@...a-project.org
Subject: Re: [PATCH v6 3/3] sound/usb: Use Media Controller API to share
 media resources

Hi Shuah,

On Thu, Dec 08, 2016 at 07:46:03AM -0700, Shuah Khan wrote:
> Hi Sakari,
> 
> On 12/07/2016 03:27 PM, Sakari Ailus wrote:
> > Hi Shuah,
> > 
> > On Wed, Dec 07, 2016 at 01:03:59PM -0700, Shuah Khan wrote:
> >> Hi Sakari,
> >>
> >> On 12/07/2016 03:52 AM, Sakari Ailus wrote:
> >>> Hi Shuah,
> >>>
> >>> On Mon, Dec 05, 2016 at 05:38:23PM -0700, Shuah Khan wrote:
> >>>> On 12/05/2016 04:21 PM, Laurent Pinchart wrote:
> >>>>> Hi Shuah,
> >>>>>
> >>>>> On Monday 05 Dec 2016 15:44:30 Shuah Khan wrote:
> >>>>>> On 11/30/2016 03:01 PM, Shuah Khan wrote:
> >>>>>>> Change ALSA driver to use Media Controller API to share media resources
> >>>>>>> with DVB, and V4L2 drivers on a AU0828 media device.
> >>>>>>>
> >>>>>>> Media Controller specific initialization is done after sound card is
> >>>>>>> registered. ALSA creates Media interface and entity function graph
> >>>>>>> nodes for Control, Mixer, PCM Playback, and PCM Capture devices.
> >>>>>>>
> >>>>>>> snd_usb_hw_params() will call Media Controller enable source handler
> >>>>>>> interface to request the media resource. If resource request is granted,
> >>>>>>> it will release it from snd_usb_hw_free(). If resource is busy, -EBUSY is
> >>>>>>> returned.
> >>>>>>>
> >>>>>>> Media specific cleanup is done in usb_audio_disconnect().
> >>>>>>>
> >>>>>>> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
> >>>>>>
> >>>>>> Hi Takashi,
> >>>>>>
> >>>>>> If you are good with this patch, could you please Ack it, so Mauro
> >>>>>> can pull it into media tree with the other two patches in this series,
> >>>>>> when he is ready to do so.
> >>>>>
> >>>>> I *really* want to address the concerns raised by Sakari before pulling more 
> >>>>> code that makes fixing the race conditions more difficult. Please, let's all 
> >>>>> work on fixing the core code to build a stable base on which we can build 
> >>>>> additional features. V4L2 and MC need teamwork, it's time to give the 
> >>>>> subsystem the love it deserves.
> >>>>>
> >>>>
> >>>> Hi Laurent,
> >>>>
> >>>> The issue Sakari brought up is specific to using devm for video_device in
> >>>> omap3 and vsp1. I tried reproducing the problem on two different drivers
> >>>> and couldn't on Linux 4.9-rc7.
> >>>>
> >>>> After sharing that with Sakari, I suggested to Sakari to pull up his patch
> >>>> that removes the devm usage and see if he still needs all the patches in his
> >>>> patch series. He didn't back to me on that. I also requested him to rebase on
> >>>
> >>> Just to see what remains, I made a small hack to test this with omap3isp by
> >>> just replacing the devm_() functions by their plain counterparts. The memory
> >>> is thus never released, for there is no really a proper moment to release it
> >>> --- something which the patchset resolves. The result is here:
> >>>
> >>> <URL:http://www.retiisi.org.uk/v4l2/tmp/media-ref-dmesg.txt>
> >>
> >> Did you test this on 4.9-rc7 without any of your other patches? If you
> >> haven't could you please run this test with just the removing devm usage
> >> from omap3isp?
> >>
> >> It would be good to get a baseline on the current with just the not using
> >> devm first and then see what needs fixing.
> >>
> >> Also, could you please send me the complete dmesg.
> > 
> > Updated from v4.9-rc6 to rc7 and with increased CONFIG_LOG_BUF_SHIFT. The
> > diff and dmesg are here:
> > 
> > <URL:http://www.retiisi.org.uk/v4l2/tmp/media-ref-diff2.txt>
> > <URL:http://www.retiisi.org.uk/v4l2/tmp/media-ref-dmesg2.txt>
> > 
> 
> Does unbind work on this even without streaming? Could you suppress

It's been working as long as I remember. There are caveats though --- the
clock to the sensor is provided by the ISP, so obviously things will not
work until the sensor is rebound as well. That is unrelated to the media
framework though; just FYI.

> debug messages and run unbind without streaming. It might fail. Let
> me know if what you see with just unbind on this driver.

I don't think disabling debug messages makes a difference but sure I can
provide you a log on that. But that'll be tomorrow.

> 
> I unearthed an old Gumstix Overo that was hiding in my hardware stash
> and I am setting it up to test.

Is it supported in mainline? I have a Nokia N9...

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@....fi	XMPP: sailus@...iisi.org.uk