cdrom: support read sub-channel command in LBA format

userspace application can send READ_SUB_CHANNEL command with time bit
enabled and disabled. The time bit allows selection of address reporting
format. If the time bit is disabled the response is in logical block
address(CDROM_LBA) format, represented as a 32-bit integer with ms-byte
first. If the time bit is enabled the response is in time format i.e.,
minutes, second, frame (CDROM_MSF) format.

Signed-off-by: vchannaiah <vanitha.channaiah@in.bosch.com>
Signed-off-by: Mahendran Kuppusamy <mahendran.kuppusamy@in.bosch.com>
[veeraiyan.chidambaram@in.bosch.com: updated Documentation/ioctl/cdrom.txt]
Signed-off-by: Veeraiyan Chidambaram <veeraiyan.chidambaram@in.bosch.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

Documentation/ioctl/cdrom.txt

@@ -340,7 +340,8 @@ CDROMSUBCHNL			Read subchannel data (struct cdrom_subchnl)
 	  EINVAL	format not CDROM_MSF or CDROM_LBA
 
 	notes:
-	  Format is converted to CDROM_MSF on return
+	  Format is converted to CDROM_MSF or CDROM_LBA
+	  as per user request on return
 
 
 

drivers/cdrom/cdrom.c

@@ -2032,7 +2032,7 @@ static int cdrom_read_subchannel(struct cdrom_device_info *cdi,
 
 	init_cdrom_command(&cgc, buffer, 16, CGC_DATA_READ);
 	cgc.cmd[0] = GPCMD_READ_SUBCHANNEL;
-	cgc.cmd[1] = 2;     /* MSF addressing */
+	cgc.cmd[1] = subchnl->cdsc_format;/* MSF or LBA addressing */
 	cgc.cmd[2] = 0x40;  /* request subQ data */
 	cgc.cmd[3] = mcn ? 2 : 1;
 	cgc.cmd[8] = 16;
@@ -2041,17 +2041,27 @@ static int cdrom_read_subchannel(struct cdrom_device_info *cdi,
 		return ret;
 
 	subchnl->cdsc_audiostatus = cgc.buffer[1];
-	subchnl->cdsc_format = CDROM_MSF;
 	subchnl->cdsc_ctrl = cgc.buffer[5] & 0xf;
 	subchnl->cdsc_trk = cgc.buffer[6];
 	subchnl->cdsc_ind = cgc.buffer[7];
 
-	subchnl->cdsc_reladdr.msf.minute = cgc.buffer[13];
-	subchnl->cdsc_reladdr.msf.second = cgc.buffer[14];
-	subchnl->cdsc_reladdr.msf.frame = cgc.buffer[15];
-	subchnl->cdsc_absaddr.msf.minute = cgc.buffer[9];
-	subchnl->cdsc_absaddr.msf.second = cgc.buffer[10];
-	subchnl->cdsc_absaddr.msf.frame = cgc.buffer[11];
+	if (subchnl->cdsc_format == CDROM_LBA) {
+		subchnl->cdsc_absaddr.lba = ((cgc.buffer[8] << 24) |
+						(cgc.buffer[9] << 16) |
+						(cgc.buffer[10] << 8) |
+						(cgc.buffer[11]));
+		subchnl->cdsc_reladdr.lba = ((cgc.buffer[12] << 24) |
+						(cgc.buffer[13] << 16) |
+						(cgc.buffer[14] << 8) |
+						(cgc.buffer[15]));
+	} else {
+		subchnl->cdsc_reladdr.msf.minute = cgc.buffer[13];
+		subchnl->cdsc_reladdr.msf.second = cgc.buffer[14];
+		subchnl->cdsc_reladdr.msf.frame = cgc.buffer[15];
+		subchnl->cdsc_absaddr.msf.minute = cgc.buffer[9];
+		subchnl->cdsc_absaddr.msf.second = cgc.buffer[10];
+		subchnl->cdsc_absaddr.msf.frame = cgc.buffer[11];
+	}
 
 	return 0;
 }
@@ -3022,7 +3032,7 @@ static noinline int mmc_ioctl_cdrom_subchannel(struct cdrom_device_info *cdi,
 	if (!((requested == CDROM_MSF) ||
 	      (requested == CDROM_LBA)))
 		return -EINVAL;
-	q.cdsc_format = CDROM_MSF;
+
 	ret = cdrom_read_subchannel(cdi, &q, 0);
 	if (ret)
 		return ret;