Messages in this thread | | | Date | Mon, 8 Sep 2003 17:28:00 +0200 | From | Samuel Thibault <> | Subject | Re: PROBLEM: Impossible to read files from a CD-Rom |
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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/
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