linux-kernel - Re: [PATCH v6 07/10] dmaengine: add dma_request_slave_channel

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Date:	Wed, 30 Jan 2013 20:38:23 -0500
From:	Matt Porter <mporter@...com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Tony Lindgren <tony@...mide.com>, "Nori, Sekhar" <nsekhar@...com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	"Cousson, Benoit" <b-cousson@...com>,
	Russell King <linux@....linux.org.uk>,
	Vinod Koul <vinod.koul@...el.com>,
	Rob Landley <rob@...dley.net>, Chris Ball <cjb@...top.org>,
	Devicetree Discuss <devicetree-discuss@...ts.ozlabs.org>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Documentation List <linux-doc@...r.kernel.org>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux SPI Devel List 
	<spi-devel-general@...ts.sourceforge.net>,
	Dan Williams <djbw@...com>,
	Rob Herring <rob.herring@...xeda.com>
Subject: Re: [PATCH v6 07/10] dmaengine: add
 dma_request_slave_channel_compat()

On Wed, Jan 30, 2013 at 09:27:18AM +0000, Arnd Bergmann wrote:
> On Wednesday 30 January 2013, Matt Porter wrote:
> > Adds a dma_request_slave_channel_compat() wrapper which accepts
> > both the arguments from dma_request_channel() and
> > dma_request_slave_channel(). Based on whether the driver is
> > instantiated via DT, the appropriate channel request call will be
> > made.
> > 
> > This allows for a much cleaner migration of drivers to the
> > dmaengine DT API as platforms continue to be mixed between those
> > that boot using DT and those that do not.
> > 
> > Suggested-by: Tony Lindgren <tony@...mide.com>
> > Signed-off-by: Matt Porter <mporter@...com>
> > Acked-by: Tony Lindgren <tony@...mide.com>
> 
> Acked-by: Arnd Bergmann <arnd@...db.de>
> 
> > @@ -1001,6 +1001,22 @@ void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
> >  struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);
> >  struct dma_chan *net_dma_find_channel(void);
> >  #define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
> > +#define dma_request_slave_channel_compat(mask, x, y, dev, name) \
> > +	__dma_request_slave_channel_compat(&(mask), x, y, dev, name)
> > +
> > +static inline struct dma_chan
> > +*__dma_request_slave_channel_compat(dma_cap_mask_t *mask, dma_filter_fn fn,
> > +				  void *fn_param, struct device *dev,
> > +				  char *name)
> > +{
> > +	struct dma_chan *chan;
> > +
> > +	chan = dma_request_slave_channel(dev, name);
> > +	if (chan)
> > +		return chan;
> > +
> > +	return __dma_request_channel(mask, fn, fn_param);
> > +}
> 
> After I have spent some more time with implementing the code for dw_dma,
> I think the mask is actually unnecessary here, the helper could just
> always set it to DMA_SLAVE before calling __dma_request_channel.
> 
> It's not a bug to do it this way though, and it may help convert drivers
> a little easier if there is less to change.

Agreed.

-Matt

> 
> 	Arnd
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