ide-cd detects wrong DVD size

From: Itay Ben-Yaacov
Date: Thu Mar 11 2004 - 00:08:00 EST


There appears to be a bug in ide-cd.c, which makes it unusable for
playing DVDs -- at some point it just stops reading. This bug does
not exist when using ide-scsi (I heard reports that short DVDs are OK).
The reason seems to be in a wrong detected size:
"blockdev --getsize" gives different results
with ide-cd and with ide-scsi+sr_mod, the latter being the correct

I believe I tracked the problem to "cdrom_read_toc()":
The following (lines 2304-2310) sets the correct capacity (line
numbers are from 2.6.3):

/* Try to get the total cdrom capacity and sector size. */
stat = cdrom_read_capacity(drive, &toc->capacity,
if (stat)
toc->capacity = 0x1fffff;

set_capacity(drive->disk, toc->capacity * sectors_per_frame);

But a bit later, on lines 2420-2425, it gets set again, this time to a
wrong value:

/* Now try to get the total cdrom capacity. */
stat = cdrom_get_last_written(cdi, &last_written);
if (!stat && last_written) {
toc->capacity = last_written;
set_capacity(drive->disk, toc->capacity *

Why is this second capacity setting there, and what is it
supposed to do exactly?

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