[MPlayer-users] linux CDROMREADRAW bug (was: Re: BUG in mplayer!)

[Tobias Diedrich]

Rainer Hantsch wrote:

> From now on I can do whatever I want (I also can software-eject the VCD!), I
> am am not able to mount any normal Data-CDROM any more, while I am still able
> to play VCD's with mplayer. :-/

Summary followup:

As Attila said this is a kernel problem.  Only certain SCSI-drives that
don't support READCD (at least for raw reads) are affected.  The kernel
then falls back to READ10 and setting the blocksize, but does not reset
it to default.  There's even a "FIXME: switch back again..." line in the
code.

Attached are a kernel patch, which I just submitted to linux-kernel, and
a userspace workaround, which does a CDROMREADMODE1 ioctl and causes the
kernel to reset the blocksize on affected drives.

Compile: gcc -o cdromreset cdromreset.c
Usage:   cdromreset < $path_to_cdrom_device

-- 
Tobias						PGP: http://9ac7e0bc.2ya.com
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--- linux-2.4.22/include/linux/cdrom.h	2003-10-28 01:30:34.000000000 +0100
+++ linux/include/linux/cdrom.h	2003-11-09 15:44:20.000000000 +0100
@@ -743,7 +743,8 @@
     	char name[20];                  /* name of the device type */
 /* per-device flags */
         __u8 sanyo_slot		: 2;	/* Sanyo 3 CD changer support */
-        __u8 reserved		: 6;	/* not used yet */
+        __u8 use_read10	: 1;		/* Use READ10 instead of READCD */
+        __u8 reserved		: 5;	/* not used yet */
 	struct cdrom_write_settings write;
 };
 
--- linux-2.4.22/drivers/cdrom/cdrom.c	2003-11-07 23:46:49.000000000 +0100
+++ linux/drivers/cdrom/cdrom.c	2003-11-09 15:52:14.000000000 +0100
@@ -1400,6 +1400,8 @@
 	return 0;
 }
 
+static int cdrom_switch_blocksize(struct cdrom_device_info *cdi, int size);
+
 /*
  * Specific READ_10 interface
  */
@@ -1408,6 +1410,7 @@
 			 int blocksize, int nblocks)
 {
 	struct cdrom_device_ops *cdo = cdi->ops;
+	int ret = 0;
 
 	memset(&cgc->cmd, 0, sizeof(cgc->cmd));
 	cgc->cmd[0] = GPCMD_READ_10;
@@ -1419,7 +1422,22 @@
 	cgc->cmd[7] = (nblocks >>  8) & 0xff;
 	cgc->cmd[8] = nblocks & 0xff;
 	cgc->buflen = blocksize * nblocks;
-	return cdo->generic_packet(cdi, cgc);
+
+	if (blocksize != CD_FRAMESIZE) {
+		ret = cdrom_switch_blocksize(cdi, blocksize);
+		ret |= cdo->generic_packet(cdi, cgc);
+		ret |= cdrom_switch_blocksize(cdi, CD_FRAMESIZE);
+	} else ret = cdo->generic_packet(cdi, cgc);
+
+	/*
+	 * Switch cdrom_read_block back to default behaviour
+	 * if we get an error.
+	 * FIXME: Maybe this should not be done on all errors.
+	 */
+	if (ret != 0)
+		cdi->use_read10 = 0;
+
+	return ret;
 }
 
 /* very generic interface for reading the various types of blocks */
@@ -1428,8 +1446,15 @@
 			    int lba, int nblocks, int format, int blksize)
 {
 	struct cdrom_device_ops *cdo = cdi->ops;
+	int ret;
+
+	if (cdi->use_read10)
+		return cdrom_read_cd(cdi, cgc, lba, blksize, nblocks);
 
 	memset(&cgc->cmd, 0, sizeof(cgc->cmd));
+	/*
+	 * SCSI-II devices are not required to support READ_CD.
+	 */
 	cgc->cmd[0] = GPCMD_READ_CD;
 	/* expected sector size - cdda,mode1,etc. */
 	cgc->cmd[1] = format << 2;
@@ -1452,7 +1477,15 @@
 	default			: cgc->cmd[9] = 0x10;
 	}
 	
-	return cdo->generic_packet(cdi, cgc);
+	ret = cdo->generic_packet(cdi, cgc);
+	if (ret && cgc->sense && cgc->sense->sense_key==0x05 && cgc->sense->asc==0x20 && cgc->sense->ascq==0x00) {
+		ret = cdrom_read_cd(cdi, cgc, lba, blksize, nblocks);
+		if (ret == 0) {
+			cdi->use_read10 = 1;
+			printk(KERN_INFO "cdrom.c: drive does not like READ_CD for blksize=%d, switching to READ_10.\n", blksize);
+		}
+	}
+	return ret;
 }
 
 /* Just about every imaginable ioctl is supported in the Uniform layer
@@ -1956,20 +1989,6 @@
 		cgc.sense = &sense;
 		cgc.data_direction = CGC_DATA_READ;
 		ret = cdrom_read_block(cdi, &cgc, lba, 1, format, blocksize);
-		if (ret && sense.sense_key==0x05 && sense.asc==0x20 && sense.ascq==0x00) {
-			/*
-			 * SCSI-II devices are not required to support
-			 * READ_CD, so let's try switching block size
-			 */
-			/* FIXME: switch back again... */
-			if ((ret = cdrom_switch_blocksize(cdi, blocksize))) {
-				kfree(cgc.buffer);
-				return ret;
-			}
-			cgc.sense = NULL;
-			ret = cdrom_read_cd(cdi, &cgc, lba, blocksize, 1);
-			ret |= cdrom_switch_blocksize(cdi, blocksize);
-		}
 		if (!ret && copy_to_user((char *)arg, cgc.buffer, blocksize))
 			ret = -EFAULT;
 		kfree(cgc.buffer);
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