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Date: Wed, 25 Apr 2007 13:34:47 -0700
From: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
To: Matt Sealey <matt@genesi-usa.com>
Cc: Olivier Galibert <galibert@pobox.com>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       jeff@garzik.org, linux-kernel@vger.kernel.org,
       linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, htejun@gmail.com
Subject: Re: [patch 1/7] libata: check for AN support
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On Wed, 25 Apr 2007 20:16:51 +0100
Matt Sealey <matt@genesi-usa.com> 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.

It's really just a coincidence that the ATA_DFLAG_AN bit is the same as the bit
in the identify device word, so this would not be appropriate.