Message-ID: <49DCB5A5.7040100@rtr.ca>
Date: Wed, 08 Apr 2009 10:33:09 -0400
From: Mark Lord <liml@rtr.ca>
Organization: Real-Time Remedies Inc.
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To: Matthew Wilcox <willy@linux.intel.com>
Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org,
       jgarzik@redhat.com, David Woodhouse <David.Woodhouse@intel.com>
Subject: Re: [PATCH 4/5] ide: Add support for TRIM
References: <1238683047-13588-1-git-send-email-willy@linux.intel.com> <1238683047-13588-2-git-send-email-willy@linux.intel.com> <1238683047-13588-3-git-send-email-willy@linux.intel.com> <1238683047-13588-4-git-send-email-willy@linux.intel.com>
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Matthew Wilcox wrote:
> From: David Woodhouse <David.Woodhouse@intel.com>
> 
> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
> [modified to reduce amount of special casing needed for discard]
> Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
> ---
..
> +	task->tf.command = ATA_CMD_DSM;
> +	task->tf.feature = ATA_DSM_TRIM;
> +	task->tf.hob_feature = 0x00;
> +	task->tf.nsect = size / 512;
> +	task->tf.hob_nsect = (size / 512) >> 8;
..

Matthew (or others),

Could you perhaps explain what the purpose of the data portion
of this command is for?  The draft ATA spec I have here has mangled
text in the description -- like it's missing a crucial sentence there.

So it's not obvious exactly why this command even needs data to
be transfered.

Thanks
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