ide-cd detects wrong DVD size

ide-cd detects wrong DVD size

[Itay Ben-Yaacov]

Hi,

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
one.

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,
&sectors_per_frame,
				   sense);
	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 *
sectors_per_frame);
	}



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

Thanks,
Itay

Re: ide-cd detects wrong DVD size

[Jens Axboe]

On Thu, Mar 11 2004, Itay Ben-Yaacov wrote:
> 
> Hi,
> 
> 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
> one.
> 
> 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,
> &sectors_per_frame,
> 				   sense);
> 	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 *
> sectors_per_frame);
> 	}

Could have sworn this was already fixed. Change the 2nd occurence to:

        if (!toc->capacity || toc->capacity == 0x1fffff) {
                stat = cdrom_get_last_written(cdi, &last_written);
                if (!stat && last_written) {
                        toc->capacity = last_written;
                        set_capacity(drive->disk, toc->capacity *
sectors_per_frame);
                }
        }

Thanks for tracking this down and reporting.

-- 
Jens Axboe