Re: 2.6.3 BUG - can't write DVD-RAM - reported as write-protected

[Jens Axboe <axboe@suse.de>]

On Tue, Mar 23 2004, Olaf Fr?czyk wrote:
> > You broke it, the first check simply returns the header so .erasable
> > must be 0 because we cleared the buffer first.
> > 
> > ===== drivers/cdrom/cdrom.c 1.49 vs edited =====
> > --- 1.49/drivers/cdrom/cdrom.c	Thu Mar 11 13:31:15 2004
> > +++ edited/drivers/cdrom/cdrom.c	Sun Mar 14 12:21:44 2004
> > @@ -2658,11 +2658,13 @@
> >  	/* set up command and get the disc info */
> >  	init_cdrom_command(&cgc, di, sizeof(*di), CGC_DATA_READ);
> >  	cgc.cmd[0] = GPCMD_READ_DISC_INFO;
> > -	cgc.cmd[8] = cgc.buflen = 2;
> > -	cgc.quiet = 1;
> > +	cgc.cmd[8] = cgc.buflen = 8;
> > +	cgc.quiet = 0;
> >  
> > -	if ((ret = cdo->generic_packet(cdi, &cgc)))
> > +	if ((ret = cdo->generic_packet(cdi, &cgc))) {
> > +		printk("cdrom: read_di failed, %d\n", ret);
> >  		return ret;
> > +	}
> >  
> >  	/* not all drives have the same disc_info length, so requeue
> >  	 * packet with the length the drive tells us it can supply
> > @@ -2673,6 +2675,7 @@
> >  	if (cgc.buflen > sizeof(disc_information))
> >  		cgc.buflen = sizeof(disc_information);
> >  
> > +	printk("cdrom: re-reading di, len=%d\n", cgc.buflen);
> >  	cgc.cmd[8] = cgc.buflen;
> >  	return cdo->generic_packet(cdi, &cgc);
> >  }
> On 2.6.4 with your patch I get:
> Mar 23 15:46:03 venus kernel: cdrom: read_di failed, -95

Ok, so your drive doesn't support GPCMD_READ_DISC_INFO at all. Probably
the best bet is simply to allow writable open if cdrom_get_disc_info()
fails after all, even though I hate doing stuff like that.

===== drivers/cdrom/cdrom.c 1.50 vs edited =====
--- 1.50/drivers/cdrom/cdrom.c	Tue Mar 16 09:41:01 2004
+++ edited/drivers/cdrom/cdrom.c	Tue Mar 23 16:23:07 2004
@@ -725,7 +725,7 @@
 	disc_information di;
 
 	if (cdrom_get_disc_info(cdi, &di))
-		return 0;
+		return -1;
 
 	return di.erasable;
 }
@@ -735,7 +735,16 @@
  */
 static int cdrom_dvdram_open_write(struct cdrom_device_info *cdi)
 {
-	return !cdrom_media_erasable(cdi);
+	int ret = cdrom_media_erasable(cdi);
+
+	/*
+	 * allow writable open if media info read worked and media is
+	 * erasable, _or_ if it fails since not all drives support it
+	 */
+	if (!ret)
+		return 1;
+
+	return 0;
 }
 
 static int cdrom_mrw_open_write(struct cdrom_device_info *cdi)

-- 
Jens Axboe