linux-kernel - Re: [PATCH 3/3] spi: rockchip: check requesting dma channel with EPROBE

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Message-ID: <20160405180804.GB8930@vkoul-mobl.iind.intel.com>
Date:	Tue, 5 Apr 2016 11:08:05 -0700
From:	Vinod Koul <vinod.koul@...el.com>
To:	Shawn Lin <shawn.lin@...k-chips.com>
Cc:	Doug Anderson <dianders@...omium.org>,
	Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH 3/3] spi: rockchip: check requesting dma channel with
 EPROBE_DEFER

On Tue, Mar 22, 2016 at 10:53:21AM +0800, Shawn Lin wrote:
> >Strange, but on 4.4 there was some extra code in
> >dma_request_slave_channel() that wasn't in
> >dma_request_slave_channel_reason().  ...but looks like that all got
> >cleaned up in the same CL that added the new name.
> 
> dma_request_chan already return ERR_PTR(-EPROBE_DEFER), but
> dma_request_slave_channel ignore this and rewrite it to be NULL.
> Strange behaviour looks to me. commit 0ad7c00057dc ("dma: add channel
> request API that supports deferred probe")  did the right thing, but
> what happened then?  It was drop for some reasons?
> 
> Hello Vinod,
> 
> Could you please elaborate some more infomation to commit 0ad7c00057dc
> ("dma: add channel request API that supports deferred probe") :) ?

The request API was cleaned up here and please see the Documentation on how
to do this.

See the commit a8135d0d7 - dmaengine: core: Introduce new, universal API to
request a channel

Thanks
-- 
~Vinod