From: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= <mans@mansr.com>
To: Vinod Koul <vinod.koul@intel.com>
Cc: Sebastian Frias <sf84@laposte.net>, 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>,
        Thibaud Cornic <thibaud_cornic@sigmadesigns.com>
Subject: Re: Tearing down DMA transfer setup after DMA client has finished
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        <20161209065955.GJ6408@localhost>
        <6ce1ea97-1d68-2203-c7b4-73315e801655@laposte.net>
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Date: Fri, 09 Dec 2016 17:28:01 +0000
In-Reply-To: <20161209171727.GK6408@localhost> (Vinod Koul's message of "Fri,
        9 Dec 2016 22:47:27 +0530")
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Vinod Koul <vinod.koul@intel.com> writes:

> On Fri, Dec 09, 2016 at 11:25:57AM +0100, Sebastian Frias wrote:
>> 
>> What concrete solution do you propose?
>
> I have already proposed two solutions.
>
> A) Request a channel only when you need it. Obviously we can't do virtual
> channels with this (though we should still use virt-channels framework).
> The sbox setup and teardown can be done as part of channel request and
> freeup. PL08x already does this.
>
> Downside is that we can only have as many consumers at a time as channels.
>
> I have not heard any technical reason for not doing this apart from drivers
> grab the channel at probe, which is incorrect and needs to be fixed
> irrespective of the problem at hand.
>
> This is my preferred option.

Sorry, but this is not acceptable.

> B) Create a custom driver specific API. This API for example:
> 	sbox_setup(bool enable, ...)
> can be called by client to explicitly setup and clear up the sbox setting.
>
> This way we can have transactions muxed.
>
> I have not heard any arguments on why we shouldn't do this except Russell's
> comment that A) solves this.

Driver-specific interfaces are not the solution.  That way lies chaos
and madness.

This would all be so much easier if you all would just shut up for a
moment and let me fix it properly.

-- 
M?ns Rullg?rd