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From: Andries.Brouwer@cwi.nl
Date: Sun, 10 Feb 2002 01:20:22 GMT
Message-Id: <UTC200202100120.BAA52437.aeb@cwi.nl>
To: alan@lxorguk.ukuu.org.uk, andre@linuxdiskcert.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] tiny IDE fixes
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org

In order to use all of my 160 GB disk, I booted linux-2.4.18-pre7-ac3
and was told that it had geometry 317632/255/63, a disk of terabyte size.
Moving the assignment to cyls two lines this becomes 19929/255/63,
as expected.

The deleted part in the first hunk is dead code.

As remarked earlier, all addr++ should be done only when
something was assigned to addr. Maybe there are more such places.

Apart from such tiny flaws, everything works beautifully.

Andre, in this geometry stuff more than half of the code can be
deleted. For example, drive->CHS is used when talking CHS with
the drive; no use assigning very large values to drive->C; nobody
will ever use such values. Then again, bios_CHS is what the BIOS
tells us, which is to be used by fdisk and lilo.
Again, no use assigning very large values to bios_cyl.
fdisk has only 10 bits to write these values in,
lilo cannot use more than 16 bits.
In particular, the ioctl HDIO_GETGEO_BIG is superfluous.

I said it before and I repeat: I really hope that you remove
all occurrences of HDIO_GETGEO_BIG. The values returned by it
are not used by fdisk, or by lilo, or by the kernel, or by
the disk drive, they are just nonsense numbers.

The convention for the use of HDIO_GETGEO is:
Get heads and sectors from HDIO_GETGEO. In case one wants
cylinders, ask for total size with BLKGETSIZE and divide by
heads*sectors. Consider the cyls field of the struct returned
by HDIO_GETGEO to be undefined.

Andries


diff -u --recursive --new-file ../linux-2.4.18-pre7-ac3/linux/drivers/ide/ide-disk.c ./linux/drivers/ide/ide-disk.c
--- ../linux-2.4.18-pre7-ac3/linux/drivers/ide/ide-disk.c	Mon Feb 11 02:53:28 2002
+++ ./linux/drivers/ide/ide-disk.c	Mon Feb 11 02:28:09 2002
@@ -111,11 +111,6 @@
 {
 	unsigned long lba_sects, chs_sects, head, tail;
 
-	if ((id->command_set_2 & 0x0400) && (id->cfs_enable_2 & 0x0400)) {
-		printk("48-bit Drive: %llu \n", id->lba_capacity_2);
-		return 1;
-	}
-
 	/*
 	 * The ATA spec tells large drives to return
 	 * C/H/S = 16383/16/63 independent of their size.
@@ -789,8 +784,8 @@
 		     | ((args.tfRegister[  IDE_HCYL_OFFSET]       ) << 16)
 		     | ((args.tfRegister[  IDE_LCYL_OFFSET]       ) <<  8)
 		     | ((args.tfRegister[IDE_SECTOR_OFFSET]       ));
+		addr++;	/* since the return value is (maxlba - 1), we add 1 */
 	}
-	addr++;	/* since the return value is (maxlba - 1), we add 1 */
 	return addr;
 }
 
@@ -818,8 +813,8 @@
 			   ((args.tfRegister[IDE_LCYL_OFFSET])<<8) |
 			    (args.tfRegister[IDE_SECTOR_OFFSET]);
 		addr = ((__u64)high << 24) | low;
+		addr++;	/* since the return value is (maxlba - 1), we add 1 */
 	}
-	addr++;	/* since the return value is (maxlba - 1), we add 1 */
 	return addr;
 }
 
@@ -850,8 +845,8 @@
 			 | ((args.tfRegister[  IDE_HCYL_OFFSET]       ) << 16)
 			 | ((args.tfRegister[  IDE_LCYL_OFFSET]       ) <<  8)
 			 | ((args.tfRegister[IDE_SECTOR_OFFSET]       ));
+		addr_set++;
 	}
-	addr_set++;
 	return addr_set;
 }
 
@@ -929,9 +924,9 @@
 
 	if (id->cfs_enable_2 & 0x0400) {
 		capacity_2 = id->lba_capacity_2;
-		drive->cyl = (unsigned int) capacity_2 / (drive->head * drive->sect);
 		drive->head		= drive->bios_head = 255;
 		drive->sect		= drive->bios_sect = 63;
+		drive->cyl = (unsigned int) capacity_2 / (drive->head * drive->sect);
 		drive->select.b.lba	= 1;
 		set_max_ext = idedisk_read_native_max_address_ext(drive);
 		if (set_max_ext > capacity_2) {
-
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