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Date: Sat, 26 Jan 2002 19:16:43 -0800
From: Andrew Morton <akpm@zip.com.au>
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To: "Kevin P. Fleming" <kevin@labsysgrp.com>
CC: lkml <linux-kernel@vger.kernel.org>
Subject: Re: [CFT] Bus mastering support for IDE CDROM audio
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"Kevin P. Fleming" wrote:
> 
> When reading from the N drive, get lots of "cdrom_pc_intr: read too
> little data 0 < 2352",

OK, thanks Kevin (Dan, Kristian, Grant..)

Seems that some devices simply terminate their DMA in a normal
manner, report no errors and don't tell us how much data they
transferred.  From my reading of the ATA spec, they're allowed
to do that - they only need to report the transfer byte count
in PIO mode.

Could you please change the code in drivers/ide/ide-cd.c:cdrom_pc_intr() to:

                if ((stat & DRQ_STAT) == 0 && len < pc->buflen) {
                        printk(__FUNCTION__ ": read too little data! %d < %d\n",
                                        len, pc->buflen);
+                       len = pc->buflen;
                }
                pc->buflen -= len;
                pc->buffer += len;

and let me know if the thing actually reads audio correctly?

Also, please tell me whether that particular drive reads normal
ISO filesystems correctly in DMA mode?   Thanks.

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