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

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Date:	Wed, 11 May 2016 15:13:22 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Måns Rullgård <mans@...sr.com>
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

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.

	Arnd