linux-kernel - Re: [PATCH 01/28] dmaengine: use DMA_COMPLETE for dma completion status

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Date:	Tue, 29 Oct 2013 09:47:55 -0700
From:	Olof Johansson <olof@...om.net>
To:	Guennadi Liakhovetski <g.liakhovetski@....de>
Cc:	Vinod Koul <vinod.koul@...el.com>,
	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>,
	Dan Williams <dan.j.williams@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Sekhar Nori <nsekhar@...com>,
	Matt Porter <matt.porter@...aro.org>
Subject: Re: [PATCH 01/28] dmaengine: use DMA_COMPLETE for dma completion status

Hi,

On Thu, Oct 24, 2013 at 11:43 PM, Guennadi Liakhovetski
<g.liakhovetski@....de> wrote:
> On Fri, 25 Oct 2013, Vinod Koul wrote:
>
>> On Fri, Oct 25, 2013 at 08:32:12AM +0200, Guennadi Liakhovetski wrote:
>> > Hi Vinod
>> >
>> > On Fri, 25 Oct 2013, Vinod Koul wrote:
>> >
>> > > On Thu, Oct 24, 2013 at 11:28:29PM +0200, Guennadi Liakhovetski wrote:
>> > > > Hi Vinod
>> > > >
>> > > > On Thu, 17 Oct 2013, Vinod Koul wrote:
>> > > > > Yes i missed it in first place update the patch to fix that
>> > > >
>> > > > Are you planning to post a fixed version of this patch or you just fix it
>> > > > internally? Would be good to have it posted to be able to ack it and other
>> > > > relevant patches.
>> > > looks like you missed it... I had posted updated patch [1] in this thread here
>> > > and I posted 29th patch as removal one [2]
>> >
>> > No, I didn't miss those, but as Sebastian pointed out and as I commented
>> > too, also that v2 version wasn't correct, so, a fixed v3 was needed.
>> > Consider this:
>> >
>> > In patch 1 you do:
>> >
>> > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
>> > index 0bc7275..683c380 100644
>> > --- a/include/linux/dmaengine.h
>> > +++ b/include/linux/dmaengine.h
>> > @@ -45,16 +45,17 @@ static inline int dma_submit_error(dma_cookie_t cookie)
>> >
>> >  /**
>> >   * enum dma_status - DMA transaction status
>> > - * @DMA_SUCCESS: transaction completed successfully
>> > + * @DMA_COMPLETE: transaction completed
>> >   * @DMA_IN_PROGRESS: transaction not yet processed
>> >   * @DMA_PAUSED: transaction is paused
>> >   * @DMA_ERROR: transaction failed
>> >   */
>> >  enum dma_status {
>> > -   DMA_SUCCESS,
>> > +   DMA_COMPLETE,
>> >     DMA_IN_PROGRESS,
>> >     DMA_PAUSED,
>> >     DMA_ERROR,
>> > +   DMA_SUCCESS,
>> >  };
>> >
>> >  /**
>> >
>> > and then in a couple of places
>> >
>> > -                   return DMA_SUCCESS;
>> > +                   return DMA_COMPLETE;
>> >
>> > So, after that your patch dmaengine would be returning DMA_COMPLETE in
>> > case of success, i.e. 0. But all the DMAC and user drivers would still be
>> > checking for
>> >
>> >     if (status != DMA_COMPLETE) {
>> >
>> > i.e. comparing status with 4 and thus detecting false errors, until your
>> > further 28 patches fix them. That's why, as Sebastian pointed out it was
>> > important to define DMA_COMPLETE and DMA_SUCCESS with the _same_ numerical
>> > value in your patch 1.
>> Sure, I will fix this up now as suggested
>>
>>   enum dma_status {
>>  -    DMA_SUCCESS,
>>  +    DMA_COMPLETE = 0, DMA_SUCCESS = 0,
>>
>> Thanks for poiting out.
>
> Great! In my reply to Sebastian I proposed an equivlent but slightly
> different version:
>
>  enum dma_status {
> -       DMA_SUCCESS,
> +       DMA_COMPLETE,
>         DMA_IN_PROGRESS,
>         DMA_PAUSED,
>         DMA_ERROR,
>  };
>
> + #define DMA_SUCCESS DMA_COMPLETE
>
> but it doesn't really matter. Feel free to use whichever version you
> prefer.


This patch broke some TI platforms (using edma) due to namespace
conflicts. The error is:

../../include/linux/dmaengine.h:54:2: error: expected identifier
before numeric constant   (for DMA_COMPLETE)

.. it's because they define DMA_COMPLETE in include/platform_data/edma.h.

The edma driver seems to overall lack prefixes and thus pollutes
global namespaces, so it should be fixed up.


-Olof
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