linux-kernel - Re: [PATCH] ata: dwc: add DMADEVICES dependency

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Date:	Wed, 11 May 2016 14:19:05 +0100
From:	Måns Rullgård <mans@...sr.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Tejun Heo <tj@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ata: dwc: add DMADEVICES dependency

Arnd Bergmann <arnd@...db.de> writes:

> On Wednesday 11 May 2016 13:57:08 Måns Rullgård wrote:
>> > diff --git a/drivers/ata/Kconfig b/drivers/ata/Kconfig
>> > index 41b0725e58ad..8f7a4a4d2566 100644
>> > --- a/drivers/ata/Kconfig
>> > +++ b/drivers/ata/Kconfig
>> > @@ -322,7 +322,7 @@ config SATA_DWC
>> >
>> >  config SATA_DWC_OLD_DMA
>> >       bool "Support old device trees"
>> > -     depends on SATA_DWC
>> > +     depends on SATA_DWC && DMADEVICES
>> >       select DW_DMAC_CORE
>> >       default y if 460EX
>> >       help
>> > -- 
>> 
>> Isn't the proper fix here to have DW_DMAC_CORE select DMADEVICES?
>
> No, all dmaengine drivers depend on DMADEVICES, so that would
> cause a circular dependency.
>
> The normal behavior for DMA slave drivers is to use the generic
> DMA API and have a dependency on DMADEVICES but not on a particular
> DMA engine implementation. In this case, the driver uses an exported
> interface of the dw_dma driver directly, so we also need to select
> that one, but it doesn't mean we can skip the normal dependency.

OK, but then shouldn't the main SATA_DWC have this dependency since it
uses the DMA API?

-- 
Måns Rullgård