linux-kernel - Re: [patch 1/7] libata: check for AN support

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Message-ID: <20070425204006.GA17784@dspnet.fr.eu.org>
Date:	Wed, 25 Apr 2007 22:40:06 +0200
From:	Olivier Galibert <galibert@...ox.com>
To:	Matt Sealey <matt@...esi-usa.com>
Cc:	Kristen Carlson Accardi <kristen.c.accardi@...el.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, jeff@...zik.org,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-ide@...r.kernel.org, htejun@...il.com
Subject: Re: [patch 1/7] libata: check for AN support

On Wed, Apr 25, 2007 at 08:16:51PM +0100, Matt Sealey wrote:
> > +#define ata_id_has_AN(id)	\
> > +	( (((id)[76] != 0x0000) && ((id)[76] != 0xffff)) && \
> > +	  ((id)[78] & (1 << 5)) )
> 
> ??
> 
> > --- 2.6-git.orig/include/linux/libata.h
> > +++ 2.6-git/include/linux/libata.h
> > @@ -136,6 +136,7 @@ enum {
> >  	ATA_DFLAG_CDB_INTR	= (1 << 2), /* device asserts INTRQ when ready for CDB */
> >  	ATA_DFLAG_NCQ		= (1 << 3), /* device supports NCQ */
> >  	ATA_DFLAG_FLUSH_EXT	= (1 << 4), /* do FLUSH_EXT instead of FLUSH */
> > +	ATA_DFLAG_AN		= (1 << 5), /* device supports Async notification */
> >  	ATA_DFLAG_CFG_MASK	= (1 << 8) - 1,
> 
> Why don't the macros use the enums? It makes the code hard to read without
> painful cross-reference doesn't it? Surely (id)[76] & (ATA_DFLAG_AN) is a
> lot more readable than 1 << 5 - even if the flag is obviously that, a lot
> of values and registers can have 1 << 5 as a flag and mean a lot of different
> things.

The two being 32 is just a coincidence.  One is a hardware register
bit, the other the signification of the bits of ata_device->flags.

  OG.

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