linux-kernel - Re: [PATCH] dmaengine: add dmanegine slave map api's

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Message-ID: <CACRpkdZHN4yw51j0-83a5Z+hoPDL2yZ11Vcx+tYHeyJMrDgVLw@mail.gmail.com>
Date:	Tue, 18 Sep 2012 23:04:13 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Vinod Koul <vinod.koul@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Dan Williams <djbw@...com>,
	Arnd Bergmann <arnd@...db.de>, Jon Hunter <jon-hunter@...com>,
	Stephen Warren <swarren@...dia.com>,
	Benoit Cousson <b-cousson@...com>,
	Shawn Guo <shawn.guo@...aro.org>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	Sascha Hauer <kernel@...gutronix.de>,
	Kukjin Kim <kgene.kim@...sung.com>,
	viresh kumar <viresh.kumar@...aro.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	Per Forlin <per.forlin@...ricsson.com>,
	Rabin VINCENT <rabin.vincent@...ricsson.com>
Subject: Re: [PATCH] dmaengine: add dmanegine slave map api's

On Tue, Sep 18, 2012 at 10:52 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:

> There's a clue in that paragraph about how the DMA engine TX descriptors
> _should_ be handled.  "hold a reference" is the clue.  Or another way to
> say it, a kref should be embedded in the structure, providing us with
> proper reference counting - and descriptors should only be 'freed'
> (whether that means actually freeing them or placing them into a free
> list) when the last reference is dropped.  That's _much_ better to
> understand than this DMA_CTRL_ACK business...

This indeed sounds like a more robust approach by far.
Why didn't we do that from the beginning ...

Yours,
Linus Walleij
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