linux-kernel - [PATCH 3.2 69/70] cdrom: Random writing support for BD-RE media

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Message-ID: <lsq.1453087115.868892992@decadent.org.uk>
Date:	Mon, 18 Jan 2016 03:18:35 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Jens Axboe" <axboe@...com>,
	"Georgios Toptsidis" <gtoptsid@...il.com>
Subject: [PATCH 3.2 69/70] cdrom: Random writing support for BD-RE media

3.2.76-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Georgios Toptsidis <gtoptsid@...il.com>

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@...com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/cdrom/cdrom.c | 1 +
 1 file changed, 1 insertion(+)

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