Re: [PATCH] ide-cd: document capacity hack

From: Sergei Shtylyov
Date: Wed Feb 18 2009 - 14:35:50 EST


Hello.

Bartlomiej Zolnierkiewicz wrote:

Just copy the comment from drivers/scsi/sr.c::sr_done()
(from which the capacity hack has been originated).

Cc: Borislav Petkov <petkovbb@xxxxxxxxx>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx>

Acked-by: Sergei Shtylyov <sshtylyov@xxxxxxxxxxxxx>

Index: b/drivers/ide/ide-cd.c
===================================================================
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -189,6 +189,14 @@ static void cdrom_analyze_sense_data(ide
bio_sectors = max(bio_sectors(failed_command->bio), 4U);
sector &= ~(bio_sectors - 1);
+ /*
+ * The SCSI specification allows for the value
+ * returned by READ CAPACITY to be up to 75 2K
+ * sectors past the last readable block.

Oh horror... :-)

+ * Therefore, if we hit a medium error within the
+ * last 75 2K sectors, we decrease the saved size
+ * value.
+ */
if (sector < get_capacity(info->disk) &&
drive->probed_capacity - sector < 4 * 75)
set_capacity(info->disk, sector);

Would be nice if the CHS capacity workround was finally documented too? ;-)

MBR, Sergei
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