Date: Thu, 8 Dec 2016 21:10:18 +0530
From: Vinod Koul <vinod.koul@intel.com>
To: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= <mans@mansr.com>
Cc: Mason <slash.tmp@free.fr>, Russell King <linux@arm.linux.org.uk>,
        dmaengine@vger.kernel.org, Linus Walleij <linus.walleij@linaro.org>,
        Dan Williams <dan.j.williams@intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Jon Mason <jdmason@kudzu.us>, Mark Brown <broonie@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>, Lee Jones <lee.jones@linaro.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Maxime Ripard <maxime.ripard@free-electrons.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Peter Ujfalusi <peter.ujfalusi@ti.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Sebastian Frias <sf84@laposte.net>,
        Thibaud Cornic <thibaud_cornic@sigmadesigns.com>
Subject: Re: Tearing down DMA transfer setup after DMA client has finished
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On Thu, Dec 08, 2016 at 11:44:53AM +0000, M?ns Rullg?rd wrote:
> Vinod Koul <vinod.koul@intel.com> writes:
> 
> > On Wed, Dec 07, 2016 at 04:45:58PM +0000, M?ns Rullg?rd wrote:
> >> Vinod Koul <vinod.koul@intel.com> writes:
> >> 
> >> > On Tue, Dec 06, 2016 at 01:14:20PM +0000, M?ns Rullg?rd wrote:
> >> >> 
> >> >> That's not going to work very well.  Device drivers typically request
> >> >> dma channels in their probe functions or when the device is opened.
> >> >> This means that reserving one of the few channels there will inevitably
> >> >> make some other device fail to operate.
> >> >
> >> > No that doesnt make sense at all, you should get a channel only when you
> >> > want to use it and not in probe!
> >> 
> >> Tell that to just about every single driver ever written.
> >
> > Not really, few do yes which is wrong but not _all_ do that.
> 
> Every driver I ever looked at does.  Name one you consider "correct."

That only tells me you haven't looked enough and want to rant!

FWIW look at ALSA-dmaengine lib, thereby every audio driver that uses it. I
could find other examples and go on and on, but that's besides the point and
looks like you don't want to listen to people telling you something..

-- 
~Vinod