On Fri, Jun 09 2000, Andries.Brouwer@cwi.nl wrote:
> Jeff complained about dd errors while reading a CDROM,
> and I also get such errors at the end, after reading all.
> The reason is that the READ CD-ROM CAPACITY command is
> not guaranteed to be precise, and indeed is not precise
> on my hardware.
Yes, agree.
> In 2.3.16 some better code was introduced, but it was
> backed out again in 2.3.17 after people complained that
> it yielded error messages. This better code uses the
> READ DISC INFORMATION command. According to my docs,
> this is a CD-R/RW only command, unavailable on an ordinary
> CDROM reader. (And my hardware agrees with my docs.)
That is true, I had hoped for better support of
READ_DISC_INFORMATIOM than what turned out to be available.
> Thus, the patch below resurrects the 2.3.16 stuff, but
> only on CD-R/RW. This means that dd now reads an image
> correctly on CD-R/RW, but still gets EIO at the end on
> a CDROM drive.
Ok, I'll accept this. As it so happens, that command is
also required for DVD drives so we can use it there as
well. Originally this was added to be more precise on
UDF file systems in particular. You haven't touched
sr either, we want to take the same approach there.
-- * Jens Axboe <axboe@suse.de> * SuSE Labs- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu Jun 15 2000 - 21:00:16 EST