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

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Message-ID: <20161209131756.GN16630@valkosipuli.retiisi.org.uk>
Date:   Fri, 9 Dec 2016 15:17:56 +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 Fri, Dec 09, 2016 at 01:44:07AM +0200, Sakari Ailus wrote:
> 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.

There you go:

<URL:http://www.retiisi.org.uk/v4l2/tmp/dmesg-test.txt>

-- 
Kind regards,

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