lkml.org 
[lkml]   [2003]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: PROBLEM: Impossible to read files from a CD-Rom
Hi,

On Mon 18 aug 2003 18:35:22 GMT, Sébastien Hinderer wrote:
> I'm using a vanila linux-2.6.0-test3.
> When I try to use a CD-Rom, the mount is successful, so are the calls to
> ls.
> However, as soon as I try to read a file, I get a lot of messages such as :
>
> hdc: rw=0, want=505092, limit=31544
> Buffer I/O error on device hdc, logical block 126272
> attempt to access beyond end of device

We dug a little bit this Monday with Sebastien, and found out some
troubles: the call to set_capacity at the end of cdrom_read_toc() writes a
strange value, which is not always the same, even for the same reinserted
CD-ROM, seemingly because it came from cdrom_get_last_written():

cdrom_get_last_written() calls cdrom_get_disc_info(), then
cdrom_get_track_info() and uses the track_start and track_size to
compute the limit of the disk. The trouble seems to come from the fact
that in cdrom_get_track_info(), the info size is got from the drive, but
no check is done to ensure that it will fill up the whole
track_information structure, which is not reset to 0 either, so that
random values remain:

(linux-2.6.0-test4/drivers/cdrom/cdrom.c:2214)
if ((ret = cdo->generic_packet(cdi, &cgc)))
return ret;

cgc.buflen = be16_to_cpu(ti->track_information_length) +
sizeof(ti->track_information_length);

if (cgc.buflen > sizeof(track_information))
cgc.buflen = sizeof(track_information);

cgc.cmd[8] = cgc.buflen;
return cdo->generic_packet(cdi, &cgc);

The solution would be to return an error if
cgc.buflen != sizeof(track_information) after the truncation to
sizeof(track_information), so that cdrom_get_last_written() will
correctly fail, and make cdrom_read_toc() use cdrom_read_capacity()
instead, which gives the correct answer.

The same remark applies to cdrom_get_disc_info().

Regards,
Samuel Thibault
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:48    [W:0.078 / U:0.144 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site