[PATCH] CDC_WR

[PATCH] CDC_WR

[Pat LaVarre]

-----Forwarded Message-----

From: Pat LaVarre <p.lavarre@ieee.org>
Subject: [PATCH] CDC_WR
Date: 10 Nov 2003 08:57:12 -0700

...:

If as yet you vote we move forward in precisely the following direction,
fine.  If not, of course I hope you can find time to redirect me.

> > a version of this CDC_MMC_WR patch
> > without the GPCMD_GET_CONFIGURATION ...
> > warn ... change ... /proc/sys/dev/cdrom/info
> > without yet changing the CDB's sent to the drive ...

The plain text inline patch of This email takes just that baby step of
distinguishing CDC_WR from CDC_DVD_RAM.

This patch is my CDC_MMC_WR patch yet again, but with my final wrong
step forward deleted.  In this patch we do Not fetch the mmc
drive-with-disc "profile" that we Now know so often appears not
"currently active".

In my quest for a solution, I hear Three relevant rumours, slanderous or
not:

1) Microsoft/ Apple/ etc. distinguish only writable discs from
unwritable discs, not writable devices from unwritable devices, so from
those precedents we get no guidance to follow in guessing what SCSI
commands will reliably tell us if a device is writable.

2) Linux sd wrestles with this same trouble, now seen in cdrom above
sr/ide-cd, for the same reason.

3) Linux doesn't yet support the write-protect tabs on dvd-ram discs, so
we can't look there to find code we can copy-edit for distinguishing
rewritable from read-only discs.

I'll work now to sort truth from fiction out of these rumours, and to
try and dream up an mmc command sequence that distinguish mmc drives
that support truly rewritable dvd discs such as dvd-ram from mmc drives
that support only the the not-so-very rewritable-in-place DVD+RW discs.

Pat LaVarre

diff -Nur linux-2.6.0-test9/drivers/cdrom/cdrom.c linux/drivers/cdrom/cdrom.c
--- linux-2.6.0-test9/drivers/cdrom/cdrom.c	2003-10-25 12:43:01.000000000 -0600
+++ linux/drivers/cdrom/cdrom.c	2003-11-10 08:41:23.000000000 -0700
@@ -313,6 +313,7 @@
 #define CHECKAUDIO if ((ret=check_for_audio_disc(cdi, cdo))) return ret
 
 /* Not-exported routines. */
+static void cdrom_get_cdc(struct cdrom_device_info *cdi);
 static int open_for_data(struct cdrom_device_info * cdi);
 static int check_for_audio_disc(struct cdrom_device_info * cdi,
 			 struct cdrom_device_ops * cdo);
@@ -381,6 +382,8 @@
 	cdinfo(CD_REG_UNREG, "drive \"/dev/%s\" registered\n", cdi->name);
 	cdi->next = topCdromPtr; 	
 	topCdromPtr = cdi;
+
+	cdrom_get_cdc(cdi);
 	return 0;
 }
 #undef ENSURE
@@ -408,6 +411,14 @@
 	return 0;
 }
 
+static void cdrom_get_cdc(struct cdrom_device_info *cdi)
+{
+	if (CDROM_CAN(CDC_WR) && !CDROM_CAN(CDC_DVD_RAM)) {
+		cdinfo(CD_REG_UNREG, "might not write well\n");
+		cdi->mask |= CDC_WR;
+	}
+}
+
 /* We use the open-option O_NONBLOCK to indicate that the
  * purpose of opening is only for subsequent ioctl() calls; no device
  * integrity checks are performed.
@@ -426,7 +437,7 @@
 	if ((fp->f_flags & O_NONBLOCK) && (cdi->options & CDO_USE_FFLAGS))
 		ret = cdi->ops->open(cdi, 1);
 	else {
-		if ((fp->f_mode & FMODE_WRITE) && !CDROM_CAN(CDC_DVD_RAM))
+		if ((fp->f_mode & FMODE_WRITE) && !CDROM_CAN(CDC_WR))
 			return -EROFS;
 
 		ret = open_for_data(cdi);
@@ -2406,6 +2417,10 @@
 	for (cdi=topCdromPtr;cdi!=NULL;cdi=cdi->next)
 	    pos += sprintf(info+pos, "\t%d", CDROM_CAN(CDC_DVD_RAM) != 0);
 
+	pos += sprintf(info+pos, "\nTolerates random write:");
+	for (cdi=topCdromPtr;cdi!=NULL;cdi=cdi->next)
+	    pos += sprintf(info+pos, "\t%d", CDROM_CAN(CDC_WR) != 0);
+
 	strcpy(info+pos,"\n\n");
 		
         return proc_dostring(ctl, write, filp, buffer, lenp);
diff -Nur linux-2.6.0-test9/include/linux/cdrom.h linux/include/linux/cdrom.h
--- linux-2.6.0-test9/include/linux/cdrom.h	2003-10-25 12:42:47.000000000 -0600
+++ linux/include/linux/cdrom.h	2003-11-10 08:28:59.000000000 -0700
@@ -388,6 +388,7 @@
 #define CDC_DVD_R		0x10000	/* drive can write DVD-R */
 #define CDC_DVD_RAM		0x20000	/* drive can write DVD-RAM */
 #define CDC_MO_DRIVE		0x40000 /* drive is an MO device */
+#define CDC_WR			0x80000	/* drive tolerates random write */
 
 /* drive status possibilities returned by CDROM_DRIVE_STATUS ioctl */
 #define CDS_NO_INFO		0	/* if not implemented */
diff -Nur linux-2.6.0-test9/drivers/ide/ide-cd.c linux/drivers/ide/ide-cd.c
--- linux-2.6.0-test9/drivers/ide/ide-cd.c	2003-10-25 12:43:32.000000000 -0600
+++ linux/drivers/ide/ide-cd.c	2003-11-10 08:41:52.000000000 -0700
@@ -2822,7 +2822,7 @@
 				CDC_MEDIA_CHANGED | CDC_PLAY_AUDIO | CDC_RESET |
 				CDC_IOCTLS | CDC_DRIVE_STATUS | CDC_CD_R |
 				CDC_CD_RW | CDC_DVD | CDC_DVD_R| CDC_DVD_RAM |
-				CDC_GENERIC_PACKET | CDC_MO_DRIVE,
+				CDC_GENERIC_PACKET | CDC_MO_DRIVE | CDC_WR,
 	.generic_packet		= ide_cdrom_packet,
 };
 
diff -Nur linux-2.6.0-test9/drivers/scsi/sr.c linux/drivers/scsi/sr.c
--- linux-2.6.0-test9/drivers/scsi/sr.c	2003-10-25 12:43:12.000000000 -0600
+++ linux/drivers/scsi/sr.c	2003-11-10 08:46:04.000000000 -0700
@@ -67,7 +67,8 @@
 	(CDC_CLOSE_TRAY|CDC_OPEN_TRAY|CDC_LOCK|CDC_SELECT_SPEED| \
 	 CDC_SELECT_DISC|CDC_MULTI_SESSION|CDC_MCN|CDC_MEDIA_CHANGED| \
 	 CDC_PLAY_AUDIO|CDC_RESET|CDC_IOCTLS|CDC_DRIVE_STATUS| \
-	 CDC_CD_R|CDC_CD_RW|CDC_DVD|CDC_DVD_R|CDC_DVD_RAM|CDC_GENERIC_PACKET)
+	 CDC_CD_R|CDC_CD_RW|CDC_DVD|CDC_DVD_R|CDC_DVD_RAM|CDC_GENERIC_PACKET| \
+	 CDC_WR)
 
 static int sr_probe(struct device *);
 static int sr_remove(struct device *);
@@ -327,8 +328,9 @@
 	}
 
 	if (rq_data_dir(SCpnt->request) == WRITE) {
-		if (!cd->device->writeable)
+		if ((cd->cdi.mask & CDC_WR) != 0) {
 			return 0;
+		}
 		SCpnt->cmnd[0] = WRITE_10;
 		SCpnt->sc_data_direction = SCSI_DATA_WRITE;
 	} else if (rq_data_dir(SCpnt->request) == READ) {
@@ -557,6 +559,7 @@
 	sdev->sector_size = 2048;	/* A guess, just in case */
 
 	/* FIXME: need to handle a get_capabilities failure properly ?? */
+	cd->device->writeable = 1; /* = ((cd->cdi.mask & CDC_WR) == 0); */
 	get_capabilities(cd);
 	sr_vendor_init(cd);
 
@@ -564,6 +567,7 @@
 			"%s/cd", sdev->devfs_name);
 	disk->driverfs_dev = &sdev->sdev_gendev;
 	register_cdrom(&cd->cdi);
+	cd->device->writeable = ((cd->cdi.mask & CDC_WR) == 0);
 	set_capacity(disk, cd->capacity);
 	disk->private_data = &cd->driver;
 	disk->queue = sdev->request_queue;
@@ -788,8 +792,6 @@
 	if ((buffer[n + 3] & 0x20) == 0) {
 		/* can't write DVD-RAM media */
 		cd->cdi.mask |= CDC_DVD_RAM;
-	} else {
-		cd->device->writeable = 1;
 	}
 	if ((buffer[n + 3] & 0x10) == 0)
 		/* can't write DVD-R media */

Re: [PATCH] CDC_WR

[Pat LaVarre]

> final wrong step forward deleted.  In this patch we do Not fetch the
> mmc drive-with-disc "profile" that we Now know so often appears not
> "currently active".
> 
> ... relevant rumours ... 1) ... 2) ... 3) ...

Slanderous or not, also I hear:

4) "Feature" x0020 RandomWritable appears present, though not "current",
in the op x46 Get Configuration data which Windows fetches to begin life
after plug in.

5) Feature x0020 appears neither present nor current in drives that
accept only the "not-so-very rewritable-in-place DVD+RW discs", rather
than "truly rewritable dvd discs such as dvd-ram".

Pat LaVarre

Re: [PATCH] CDC_WR

[Pat LaVarre]

> Slanderous or not, also I hear:

6) We may have good precedent for our idea of (a) fetch header, (b)
interpret additional length, then (c) fetch all available op x46 Get
Configuration data.

Specifically we have one sample of Windows XP SP1 starting life after
plug in with that politically correct speech:

http://marc.theaimsgroup.com/?l=linux-scsi&m=106858800007411

List: linux-scsi
Subject: Re: usb storage traces
Date: 2003-11-11 21:59:22

7) Fetching all the device configuration this way lets us see the
"profile list".  Testing whetrher the profile list contains one or more
writable profiles, none of which are DVD+RW, might be our best mmc way
of guessing if open of device should fail via EROFS or no.

Pat LaVarre

Re: [PATCH] CDC_WR

[Pat LaVarre]

Calling all MMC gurus ...

> > Slanderous or not, also I hear:
> ...
> 7) Fetching all the device configuration this way lets us see the
> "profile list".  Testing whetrher the profile list contains one or more
> writable profiles, none of which are DVD+RW, might be our best mmc way
> of guessing if open of device should fail via EROFS or no.

Ouch, not so good.

The DVD-ROM drive in my cube reports profiles 0010 000A 0009 0008 0002 =
DVD-ROM, CD-RW, CD-R, CD-ROM, Removable Disk.

I think next I will try saying the current-or-not presence of any
non-standard profile, or of any MMC profile that does not require
feature x0020 Random Writable, implies not-writable, but the
current-or-not presence of feature x0020 Random Wruitable implies
yes-writable.

Pat LaVarre

Re: [PATCH] CDC_WR

[Pat LaVarre]

Calling all MMC gurus ...

> > > Slanderous or not, also I hear:

8)

In Japanese we have:

http://pc.watch.impress.co.jp/docs/2003/0401/hitachi.htm

I'm told this says LG-Hitachi makes a drive that supports all three of
the dominant three kinds of discs: DVD-RAM and DVD-RW and DVD+RW.

In 2.6.0-test9 cdrom.ko, that drive will appear writable via mode page
x2A Capabilities by saying DVD-RAM disc could appear, no matter if the
inserted disc is DVD+RW i.e. not very rewritable-in-place.

Ouch.

Pat LaVarre

Re: [PATCH] CDC_WR

[Pat LaVarre]

The inline patch of this post sketches how we might choose to teach
cdrom.ko to interpret MMC features ... after we decide what
interpretation we like.

As is, this code clearly still needs work e.g. it says more cdrom.ko
devices are writable then we mean to consider writable, and it goes
badly wrong if ever a device reports more than xFFFF bytes of features
available.

Meanwhile, for the sake of development, as yet this patch conveniently
spits out a dump of all the "feature code"s and "profile"s.

For example, the dmesg I saw from a device that mixes not-current
profile x0002 "Removable Disk" together with not-current feature code
"x0020 "Random Writable" ... despite not actually supporting much
rewrite in place was:

hdc: ATAPI 48X DVD-ROM CD-R/RW drive, 2048kB Cache, UDMA(33)
cdrom: entering register_cdrom
Uniform CD-ROM driver Revision: 3.12
cdrom: drive "/dev/hdc" registered
cdrom: may be writable
cdrom: feature code x0000
cdrom: profile x0010
cdrom: profile x000A
cdrom: profile x0009
cdrom: profile x0008
cdrom: profile x0002 // Removable Disk
cdrom: feature code x0001
cdrom: feature code x0002
cdrom: feature code x0003
cdrom: feature code x0010
cdrom: feature code x001D
cdrom: feature code x001E
cdrom: feature code x001F
cdrom: feature code x0020 // Random Writable
cdrom: feature code x0021
cdrom: feature code x0023
cdrom: feature code x0024
cdrom: feature code x0026
cdrom: feature code x0027
cdrom: feature code x0028
cdrom: feature code x002A
cdrom: feature code x002B
cdrom: feature code x002D
cdrom: feature code x002E
cdrom: feature code x0100
cdrom: feature code x0101
cdrom: feature code x0103
cdrom: feature code x0104
cdrom: feature code x0105
cdrom: feature code x0106
cdrom: feature code x0107
cdrom: entering cdrom_open
...

Pat LaVarre

diff -Nur linux-2.6.0-test9/drivers/cdrom/cdrom.c linux/drivers/cdrom/cdrom.c
--- linux-2.6.0-test9/drivers/cdrom/cdrom.c	2003-10-25 12:43:01.000000000 -0600
+++ linux/drivers/cdrom/cdrom.c	2003-11-13 15:50:38.000000000 -0700
@@ -251,6 +251,9 @@
 /* #define ERRLOGMASK (CD_WARNING|CD_OPEN|CD_COUNT_TRACKS|CD_CLOSE) */
 /* #define ERRLOGMASK (CD_WARNING|CD_REG_UNREG|CD_DO_IOCTL|CD_OPEN|CD_CLOSE|CD_COUNT_TRACKS) */
 
+#undef ERRLOGMASK
+#define ERRLOGMASK (CD_WARNING|CD_REG_UNREG|CD_DO_IOCTL|CD_OPEN|CD_CLOSE|CD_COUNT_TRACKS)
+
 #include <linux/config.h>
 #include <linux/module.h>
 #include <linux/fs.h>
@@ -313,6 +316,7 @@
 #define CHECKAUDIO if ((ret=check_for_audio_disc(cdi, cdo))) return ret
 
 /* Not-exported routines. */
+static void cdrom_get_cdc(struct cdrom_device_info *cdi);
 static int open_for_data(struct cdrom_device_info * cdi);
 static int check_for_audio_disc(struct cdrom_device_info * cdi,
 			 struct cdrom_device_ops * cdo);
@@ -381,6 +385,8 @@
 	cdinfo(CD_REG_UNREG, "drive \"/dev/%s\" registered\n", cdi->name);
 	cdi->next = topCdromPtr; 	
 	topCdromPtr = cdi;
+
+	cdrom_get_cdc(cdi);
 	return 0;
 }
 #undef ENSURE
@@ -408,6 +414,114 @@
 	return 0;
 }
 
+/* Interpret the MMC feature x0000 "Profile List". */
+
+static int cdrom_profile_list(struct cdrom_device_info *cdi,
+	u_char * buf, int len)
+{
+	int offset;
+	for (offset = 4; (offset + 4) <= len; offset += 4) {
+		int profile = buf[offset] << 8 | buf[offset + 1];
+		cdinfo(CD_REG_UNREG, "profile x%04X\n", profile);
+		switch (profile) {
+			case 0x0001: /* Non-Removable Disk */
+			case 0x0002: /* Removable Disk */
+			case 0x0003: /* Magneto-Optical Erasable */
+			case 0x0005: /* AS-MO */
+			case 0x0012: /* DVD-RAM */
+			case 0x0022: /* DDCD-RW */
+				break;
+			case 0x001A: /* DVD+RW = not much rewrite in place */
+			default:
+				cdi->mask |= CDC_WR;
+				break;
+		}
+	}
+	return 0;
+}
+
+/* Interpret an MMC feature. */
+
+static int cdrom_feature(struct cdrom_device_info *cdi,
+	u_char * buf, int len)
+{
+	int feature_code = buf[0] << 8 | buf[1];
+	cdinfo(CD_REG_UNREG, "feature code x%04X\n", feature_code);
+	switch (feature_code) {
+		case 0x0000: /* "Profile List" */
+			cdrom_profile_list(cdi, buf, len);
+			break;
+		case 0x0020: /* "Random Writable" */
+			cdi->mask &= ~CDC_WR;
+			break;
+		default:
+			break;
+	}
+	return 0;
+}
+
+/* Interpret each MMC feature in order per mmc4r02f.pdf. */
+
+static int cdrom_each_feature(struct cdrom_device_info *cdi,
+	u_char * buf, int len)
+{
+	int ret = 0;
+	int offset;
+	int step;
+	for (offset = 8; (offset + 4) <= len; offset += step) {
+		step = (3 + 1 + buf[offset + 3]);
+		if ((offset + step) <= len) {
+			ret |= cdrom_feature(cdi, &buf[offset], step);
+		}
+	}
+	return ret;
+}
+
+/* Fetch the first few available MMC "feature"s. */
+
+static int cdrom_get_configuration(struct cdrom_device_info *cdi)
+{
+	struct cdrom_generic_command cgc;
+	struct cdrom_device_ops *cdo = cdi->ops;
+	u_char part[8];
+	int ret;
+	init_cdrom_command(&cgc, part, 8, CGC_DATA_READ);
+	cgc.cmd[0] = GPCMD_GET_CONFIGURATION; /* 0x46 */
+	cgc.cmd[7] = cgc.buflen >> 8;
+	cgc.cmd[8] = cgc.buflen & 0xff;
+	ret = cdo->generic_packet(cdi, &cgc);
+	if (!ret) {
+		int len = (4 + 0 + (part[0] << 24 | part[1] << 16 |
+			part[2] << 8 | part[3]));
+		u_char * whole = kmalloc(len, GFP_KERNEL);
+		if (!whole)
+			return -ENOMEM;
+		init_cdrom_command(&cgc, whole, len, CGC_DATA_READ);
+		cgc.cmd[0] = GPCMD_GET_CONFIGURATION; /* 0x46 */
+		cgc.cmd[7] = cgc.buflen >> 8;
+		cgc.cmd[8] = cgc.buflen & 0xff;
+		ret = cdo->generic_packet(cdi, &cgc);
+		if (!ret) {
+			ret = cdrom_each_feature(cdi, whole, len);
+		}
+		kfree(whole);
+	}
+	return ret;
+}
+
+/* Tweak cdi->mask to agree with MMC "feature" descriptors. */
+
+static void cdrom_get_cdc(struct cdrom_device_info *cdi)
+{
+	if (CDROM_CAN(CDC_WR) && !CDROM_CAN(CDC_DVD_RAM)) {
+		cdinfo(CD_REG_UNREG, "may be writable\n");
+		cdi->mask |= CDC_WR; /* guess not */
+		if (cdrom_get_configuration(cdi)) {
+			cdinfo(CD_REG_UNREG, "indeterminate features\n");
+		}
+	}
+}
+
 /* We use the open-option O_NONBLOCK to indicate that the
  * purpose of opening is only for subsequent ioctl() calls; no device
  * integrity checks are performed.
@@ -426,7 +540,7 @@
 	if ((fp->f_flags & O_NONBLOCK) && (cdi->options & CDO_USE_FFLAGS))
 		ret = cdi->ops->open(cdi, 1);
 	else {
-		if ((fp->f_mode & FMODE_WRITE) && !CDROM_CAN(CDC_DVD_RAM))
+		if ((fp->f_mode & FMODE_WRITE) && !CDROM_CAN(CDC_WR))
 			return -EROFS;
 
 		ret = open_for_data(cdi);
@@ -2406,6 +2520,10 @@
 	for (cdi=topCdromPtr;cdi!=NULL;cdi=cdi->next)
 	    pos += sprintf(info+pos, "\t%d", CDROM_CAN(CDC_DVD_RAM) != 0);
 
+	pos += sprintf(info+pos, "\nTolerates random write:");
+	for (cdi=topCdromPtr;cdi!=NULL;cdi=cdi->next)
+	    pos += sprintf(info+pos, "\t%d", CDROM_CAN(CDC_WR) != 0);
+
 	strcpy(info+pos,"\n\n");
 		
         return proc_dostring(ctl, write, filp, buffer, lenp);
diff -Nur linux-2.6.0-test9/include/linux/cdrom.h linux/include/linux/cdrom.h
--- linux-2.6.0-test9/include/linux/cdrom.h	2003-10-25 12:42:47.000000000 -0600
+++ linux/include/linux/cdrom.h	2003-11-10 08:28:59.000000000 -0700
@@ -388,6 +388,7 @@
 #define CDC_DVD_R		0x10000	/* drive can write DVD-R */
 #define CDC_DVD_RAM		0x20000	/* drive can write DVD-RAM */
 #define CDC_MO_DRIVE		0x40000 /* drive is an MO device */
+#define CDC_WR			0x80000	/* drive tolerates random write */
 
 /* drive status possibilities returned by CDROM_DRIVE_STATUS ioctl */
 #define CDS_NO_INFO		0	/* if not implemented */
diff -Nur linux-2.6.0-test9/drivers/ide/ide-cd.c linux/drivers/ide/ide-cd.c
--- linux-2.6.0-test9/drivers/ide/ide-cd.c	2003-10-25 12:43:32.000000000 -0600
+++ linux/drivers/ide/ide-cd.c	2003-11-10 08:41:52.000000000 -0700
@@ -2822,7 +2822,7 @@
 				CDC_MEDIA_CHANGED | CDC_PLAY_AUDIO | CDC_RESET |
 				CDC_IOCTLS | CDC_DRIVE_STATUS | CDC_CD_R |
 				CDC_CD_RW | CDC_DVD | CDC_DVD_R| CDC_DVD_RAM |
-				CDC_GENERIC_PACKET | CDC_MO_DRIVE,
+				CDC_GENERIC_PACKET | CDC_MO_DRIVE | CDC_WR,
 	.generic_packet		= ide_cdrom_packet,
 };
 
diff -Nur linux-2.6.0-test9/drivers/scsi/sr.c linux/drivers/scsi/sr.c
--- linux-2.6.0-test9/drivers/scsi/sr.c	2003-10-25 12:43:12.000000000 -0600
+++ linux/drivers/scsi/sr.c	2003-11-10 08:46:04.000000000 -0700
@@ -67,7 +67,8 @@
 	(CDC_CLOSE_TRAY|CDC_OPEN_TRAY|CDC_LOCK|CDC_SELECT_SPEED| \
 	 CDC_SELECT_DISC|CDC_MULTI_SESSION|CDC_MCN|CDC_MEDIA_CHANGED| \
 	 CDC_PLAY_AUDIO|CDC_RESET|CDC_IOCTLS|CDC_DRIVE_STATUS| \
-	 CDC_CD_R|CDC_CD_RW|CDC_DVD|CDC_DVD_R|CDC_DVD_RAM|CDC_GENERIC_PACKET)
+	 CDC_CD_R|CDC_CD_RW|CDC_DVD|CDC_DVD_R|CDC_DVD_RAM|CDC_GENERIC_PACKET| \
+	 CDC_WR)
 
 static int sr_probe(struct device *);
 static int sr_remove(struct device *);
@@ -327,8 +328,9 @@
 	}
 
 	if (rq_data_dir(SCpnt->request) == WRITE) {
-		if (!cd->device->writeable)
+		if ((cd->cdi.mask & CDC_WR) != 0) {
 			return 0;
+		}
 		SCpnt->cmnd[0] = WRITE_10;
 		SCpnt->sc_data_direction = SCSI_DATA_WRITE;
 	} else if (rq_data_dir(SCpnt->request) == READ) {
@@ -557,6 +559,7 @@
 	sdev->sector_size = 2048;	/* A guess, just in case */
 
 	/* FIXME: need to handle a get_capabilities failure properly ?? */
+	cd->device->writeable = 1; /* = ((cd->cdi.mask & CDC_WR) == 0); */
 	get_capabilities(cd);
 	sr_vendor_init(cd);
 
@@ -564,6 +567,7 @@
 			"%s/cd", sdev->devfs_name);
 	disk->driverfs_dev = &sdev->sdev_gendev;
 	register_cdrom(&cd->cdi);
+	cd->device->writeable = ((cd->cdi.mask & CDC_WR) == 0);
 	set_capacity(disk, cd->capacity);
 	disk->private_data = &cd->driver;
 	disk->queue = sdev->request_queue;
@@ -788,8 +792,6 @@
 	if ((buffer[n + 3] & 0x20) == 0) {
 		/* can't write DVD-RAM media */
 		cd->cdi.mask |= CDC_DVD_RAM;
-	} else {
-		cd->device->writeable = 1;
 	}
 	if ((buffer[n + 3] & 0x10) == 0)
 		/* can't write DVD-R media */