linux-kernel - Re: [PATCH] Cleanup libata HPA support

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Message-Id: <1178635394.6962.97.camel@cunning>
Date:	Tue, 08 May 2007 16:43:14 +0200
From:	Ben Collins <ben.collins@...ntu.com>
To:	Mark Lord <liml@....ca>
Cc:	linux-kernel@...r.kernel.org, alan@...rguk.ukuu.org.uk,
	Kyle McMartin <kyle@...ntu.com>, linux-ide@...r.kernel.org
Subject: Re: [PATCH] Cleanup libata HPA support

On Tue, 2007-05-08 at 09:44 -0400, Mark Lord wrote:
> Ben Collins wrote:
> ..
> >  static u64 ata_tf_to_lba48(struct ata_taskfile *tf)
> >  {
> > -	u64 sectors = 0;
> > +	u64 sectors;
> > +	u32 high, low;
> >  
> > -	sectors |= ((u64)(tf->hob_lbah & 0xff)) << 40;
> > -	sectors |= ((u64)(tf->hob_lbam & 0xff)) << 32;
> > -	sectors |= (tf->hob_lbal & 0xff) << 24;
> > -	sectors |= (tf->lbah & 0xff) << 16;
> > -	sectors |= (tf->lbam & 0xff) << 8;
> > -	sectors |= (tf->lbal & 0xff);
> > +	high = (tf->hob_lbah << 16) |
> > +	       (tf->hob_lbam <<  8) |
> > +		tf->hob_lbal;
> > +	low  = (tf->lbah << 16) |
> > +	       (tf->lbam <<  8) |
> > +		tf->lbal;
> >  
> > -	return ++sectors;
> > +	sectors = ((u64)high << 24) | low;
> > +
> > +	return sectors + 1;
> >  }
> 
> Ben, I very much prefer the fixed version of this function
> as implemented by the patch above.
> 
> But.. is the original code actually broken, or just messy?

Due to the bugs we were seeing, we actually noticed that this function
was having signed extension issues as originally implemented. I didn't
look for the actual bug, but reimplemented it based on code in
ide_disk.c, which resolved the issue.

-- 
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