[PATCH] cdrom: support Beurer GL50 evo CD-on-a-chip devices.

["Diego Elio Pettenò" <flameeyes@flameeyes.com>]

The Beurer GL50 evo uses a Cygnal/Cypress-manufactured CD-on-a-chip that
only accepts a subset of SCSI commands.

Most of the not-implemented commands are fine to fail, but a few,
particularly around the MMC or Audio commands, will put the device into an
unrecoverable state, so they need to be avoided at all costs.

In addition to adding a new vendor entry to sr_vendor, this required gating
a few functions in the cdrom driver to not even try sending the command
when the capability is not present.

Cc: linux-scsi@vger.kernel.org
Signed-off-by: Diego Elio Pettenò <flameeyes@flameeyes.com>
---
 drivers/cdrom/cdrom.c    | 13 ++++++++++++-
 drivers/scsi/sr_vendor.c | 18 ++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index ac42ae4651ce..2391b5dd36a9 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -996,6 +996,12 @@ static void cdrom_count_tracks(struct cdrom_device_info *cdi, tracktype *tracks)
 	tracks->xa = 0;
 	tracks->error = 0;
 	cd_dbg(CD_COUNT_TRACKS, "entering cdrom_count_tracks\n");
+
+	if (!CDROM_CAN(CDC_PLAY_AUDIO)) {
+		tracks->error = CDS_NO_INFO;
+		return;
+	}
+
 	/* Grab the TOC header so we can see how many tracks there are */
 	ret = cdi->ops->audio_ioctl(cdi, CDROMREADTOCHDR, &header);
 	if (ret) {
@@ -1162,7 +1168,9 @@ int cdrom_open(struct cdrom_device_info *cdi, struct block_device *bdev,
 		ret = open_for_data(cdi);
 		if (ret)
 			goto err;
-		cdrom_mmc3_profile(cdi);
+		if (CDROM_CAN(CDC_GENERIC_PACKET)) {
+			cdrom_mmc3_profile(cdi);
+		}
 		if (mode & FMODE_WRITE) {
 			ret = -EROFS;
 			if (cdrom_open_write(cdi))
@@ -2882,6 +2890,9 @@ int cdrom_get_last_written(struct cdrom_device_info *cdi, long *last_written)
 	   it doesn't give enough information or fails. then we return
 	   the toc contents. */
 use_toc:
+	if (!CDROM_CAN(CDC_PLAY_AUDIO))
+		return -ENOSYS;
+
 	toc.cdte_format = CDROM_MSF;
 	toc.cdte_track = CDROM_LEADOUT;
 	if ((ret = cdi->ops->audio_ioctl(cdi, CDROMREADTOCENTRY, &toc)))
diff --git a/drivers/scsi/sr_vendor.c b/drivers/scsi/sr_vendor.c
index e3b0ce25162b..b5e76869d473 100644
--- a/drivers/scsi/sr_vendor.c
+++ b/drivers/scsi/sr_vendor.c
@@ -61,6 +61,7 @@
 #define VENDOR_NEC             2
 #define VENDOR_TOSHIBA         3
 #define VENDOR_WRITER          4	/* pre-scsi3 writers */
+#define VENDOR_CYGNAL_85ED     5	/* CD-on-a-chip */
 
 #define VENDOR_TIMEOUT	30*HZ
 
@@ -99,6 +100,23 @@ void sr_vendor_init(Scsi_CD *cd)
 	} else if (!strncmp(vendor, "TOSHIBA", 7)) {
 		cd->vendor = VENDOR_TOSHIBA;
 
+	} else if (!strncmp(vendor, "Beurer", 6) &&
+		   !strncmp(model, "Gluco Memory", 12)) {
+		/* The Beurer GL50 evo uses a Cygnal/Cypress-manufactured
+		   CD-on-a-chip that only accepts a subset of SCSI commands.
+		   Most of the not-implemented commands are fine to fail, but a
+		   few, particularly around the MMC or Audio commands, will put
+		   the device into an unrecoverable state, so they need to be
+		   avoided at all costs.
+		*/
+		cd->vendor = VENDOR_CYGNAL_85ED;
+		cd->cdi.mask |= (
+			CDC_MULTI_SESSION |
+			CDC_CLOSE_TRAY | CDC_OPEN_TRAY |
+			CDC_LOCK |
+			CDC_GENERIC_PACKET |
+			CDC_PLAY_AUDIO
+			);
 	}
 #endif
 }
-- 
2.23.0