linux-kernel - Re: [PATCH v2 1/2] dmaengine: Add an enum for the dmaengine alignment constraints

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Message-ID: <20150727064804.GN2564@lukather>
Date:	Mon, 27 Jul 2015 08:48:04 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Cc:	Vinod Koul <vinod.koul@...el.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] dmaengine: Add an enum for the dmaengine
 alignment constraints

On Mon, Jul 20, 2015 at 11:03:25AM +0200, Thomas Petazzoni wrote:
> Maxime,
> 
> On Mon, 20 Jul 2015 10:41:32 +0200, Maxime Ripard wrote:
> 
> >  /**
> > + * enum dmaengine_alignment - defines alignment of the DMA async tx
> > + * buffers
> > + */
> > +enum dmaengine_alignment {
> > +	DMAENGINE_ALIGN_1_BYTE = 0,
> > +	DMAENGINE_ALIGN_2_BYTES = 1,
> > +	DMAENGINE_ALIGN_4_BYTES = 2,
> > +	DMAENGINE_ALIGN_8_BYTES = 3,
> > +	DMAENGINE_ALIGN_16_BYTES = 4,
> > +	DMAENGINE_ALIGN_32_BYTES = 5,
> > +	DMAENGINE_ALIGN_64_BYTES = 6,
> > +};
> 
> Sorry I didn't think about this during the first iteration, but this
> define is just the log2 of the values, no? So maybe you could simply do
> something like:
> 
> static inline unsigned int dmaengine_alignment(size_t bytes)
> {
> 	return ilog2(bytes);
> }

I could, but all the rest of the other similar case so far in
dmaengine are made through enum, so I guess it's still better for
consistency. And we also provide a comprehensive list of the valid
values this way, something a function would not provide (or at least
not at compilation time)

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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