Subject: Resend: PATCH: Stop 2.6.12rc rmmod from being able to destroy CD
	hardware
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, axboe@suse.de,
       Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>,
       torvalds@osdl.org
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Date: Fri, 27 May 2005 13:18:08 +0100
Sender: linux-kernel-owner@vger.kernel.org
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On an rmmod the cdrom layer when used with ide-cd issues a cache flush
atapi command to devices including those that do not support it.
According to Jens earlier discussion this isn't merely a minor glitch
but can destroy some CD hardware due to firmware bugs in the drive (as
per the Mandrake incident)

The IDE CD layer uses a mask of unsupported features, this means that
because ide-cd doesn't know about MRW writables it doesn't set the
relevant bit for non writables and harm can occur.

The simple fix is attached, making the driver start from ~0 and mask
bits the other direction would longer term be safer.

diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.12rc3/drivers/ide/ide-cd.c linux-2.6.12rc3-minoride/drivers/ide/ide-cd.c
--- linux.vanilla-2.6.12rc3/drivers/ide/ide-cd.c	2005-04-27 16:01:29.000000000 +0100
+++ linux-2.6.12rc3-minoride/drivers/ide/ide-cd.c	2005-05-01 14:09:35.000000000 +0100
@@ -2860,6 +2922,9 @@
 		devinfo->mask |= CDC_CLOSE_TRAY;
 	if (!CDROM_CONFIG_FLAGS(drive)->mo_drive)
 		devinfo->mask |= CDC_MO_DRIVE;
+		
+	/* We must have this masked unless a drive definitely handles it */
+	devinfo->mask |= CDC_MRW_W;
 
 	devinfo->disk = info->disk;
 	return register_cdrom(devinfo);

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