linux-kernel - Re: [PATCH 1/3] dmaengine: Allow controller drivers to set channel ids

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Message-ID: <4ED30893.6080601@st.com>
Date:	Mon, 28 Nov 2011 09:35:39 +0530
From:	Viresh Kumar <viresh.kumar@...com>
To:	Vinod Koul <vinod.koul@...el.com>, Dan <dan.j.williams@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Armando VISCONTI <armando.visconti@...com>,
	Shiraz HASHIM <shiraz.hashim@...com>,
	Vipin KUMAR <vipin.kumar@...com>,
	Rajeev KUMAR <rajeev-dlh.kumar@...com>,
	Deepak SIKRI <deepak.sikri@...com>,
	Vipul Kumar SAMAR <vipulkumar.samar@...com>,
	Amit VIRDI <Amit.VIRDI@...com>,
	Pratyush ANAND <pratyush.anand@...com>,
	Bhupesh SHARMA <bhupesh.sharma@...com>,
	"viresh.linux@...il.com" <viresh.linux@...il.com>,
	Bhavna YADAV <bhavna.yadav@...com>
Subject: Re: [PATCH 1/3] dmaengine: Allow controller drivers to set channel
 ids

On 9/28/2011 2:38 PM, Vinod Koul wrote:
> On Thu, 2011-09-22 at 16:13 +0530, Viresh Kumar wrote:
>> > Currently value of chan_id field is updated by dmaengine.c while the dma device
>> > is registered. In some cases the controller driver may need to assign channel
>> > numbers by itself. For example, dw_dmac.c wants to control the order in which
>> > channels are allocated by dmaengine. So it added channels inside channel list of
>> > dma_device in reverse order. Now channel 7 is allocated first and channel 0 is
>> > allocated last.
>> > 
>> > But as the channel ids are updated by dmaengine, channel numbers in sysfs will
>> > be overwritten if controller has added channels in reverse order. To represent
>> > correct channel number in sysfs, it is required that dmaengine must not assume
>> > that first channel in list is channel 0 and last is 7.
> to dmaengine, this is just a channel representation in sysfs and nothing
> more. If damc is assuming that this is same as what dmaengine will do
> then dmac is wrong.
> 
> Nevertheless, Dan was okay with changing this representation.
> Dan I would need your comments/Ack before we discuss this further

Dan/Vinod,

Any feedback on this patchset?

-- 
viresh
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