cdrom: Random writing support for BD-RE media

commit f7e7868b4743f1cc5e59e6e0ddd3ccf9cfe53a1b upstream.

Recently, i bought a blu-ray writer and noticed that while cdrecord
worked perfectly, random writing didn't work on rewritable bd-re media.
For example, dd if=/dev/zero of=/dev/sr0 bs=32768 count=2 gave the usual
"read-only file system" message.

After checking if the problem lies with my burner or firmware, i grep-ed
the kernel source for EROFS. One of the results was in the cdrom driver.

I tried to follow the function chain and ended in the cdrom_is_dvd_rw
function where writing is permitted only for DVD-RAM and DVD+RW media.
I added a new case label for 0x43 which is the profile name of BD-RE
and now it works correctly for BD-RE too.

Maybe there is a better way of implementing this, like a new function
checking for blu-ray support and called from cdrom_open_write like
it happens for mrw and dvdram media, but adding the case label worked.

Thank you for your time.

Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index 1331740..a03e849 100644 (file)
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -873,6 +873,7 @@ static int cdrom_is_dvd_rw(struct cdrom_device_info *cdi)
        switch (cdi->mmc3_profile) {
        case 0x12:      /* DVD-RAM      */
        case 0x1A:      /* DVD+RW       */
+       case 0x43:      /* BD-RE        */
                return 0;
        default:
                return 1;