From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 2/3] block layer varlen-cdb
Date: Tue, 12 Feb 2008 12:48:08 -0500
Message-ID: <20080212174808.GB26316@infradead.org>
References: <20080209193224.GA21448@Chamillionaire.breakpoint.cc> <200802100006.11086.bzolnier@gmail.com> <20080210052621.GA22257@infradead.org> <200802101438.46698.bzolnier@gmail.com> <20080210144352.GA3537@infradead.org> <47AF1321.7000107@panasas.com> <47AF4974.9010200@panasas.com> <47AF4BF5.90807@panasas.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Return-path: <linux-scsi-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <47AF4BF5.90807@panasas.com>
Sender: linux-scsi-owner@vger.kernel.org
To: Boaz Harrosh <bharrosh@panasas.com>
Cc: Christoph Hellwig <hch@infradead.org>, Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>, Jens Axboe <jens.axboe@oracle.com>, James Bottomley <James.Bottomley@hansenpartnership.com>, Sebastian Siewior <ide+bug@ml.breakpoint.cc>, Tejun Heo <htejun@gmail.com>, Sergei Shtylyov <sshtylyov@ru.mvista.com>, linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org
List-Id: linux-ide@vger.kernel.org

On Sun, Feb 10, 2008 at 09:09:41PM +0200, Boaz Harrosh wrote:
> - add varlen_cdb and varlen_cdb_len to hold a large user cdb
>   if needed. They start as empty. Allocation of buffer must
>   be done by user and held until request execution is done.
> - Since there can be either a fix_length command up to 16 bytes
>   or a variable_length, larger then 16 bytes, commands but never
>   both, we hold the two types in a union to save space. The
>   presence of varlen_cdb_len and cmd_len==0 signals a varlen_cdb
>   mode.

this one I'm a bit confused by, why can't we just set the length
of the variable length command in cmd_len aswell, and if cmd_len >
the length of the cmd array it's a variable length command?

Note that this is both to keep the logic simpler and not to grow
struct request further.  Especially for the rather rare case
of a bidi command.