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

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Message-ID: <3357570.y2pHcSUkFV@wuerfel>
Date:	Wed, 11 May 2016 15:32:18 +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 14:19:05 Måns Rullgård wrote:
> 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?
> 

Right, I missed that and thought only the SATA_DWC_OLD_DMA variant
used dmaengine at all. I'll send a new version of my patch then.

Thanks,

	Arnd