[syslinux] BIOS disk geometry and Linux 2.6
Michael_E_Brown at Dell.com
Michael_E_Brown at Dell.com
Fri Feb 27 13:16:37 PST 2004
Matt,
Some EDD changes. Please see the archives for syslinux mailing list
for discussion. Patrick can provide more commentary on this, but it appears
that EDD is returning the wrong geometry.
Patric,
You should talk directly with Matt about this patch. I'd rather not
be a bottleneck, since I am now in a different group than Matt. Also, please
be aware that Matt is out for a couple of weeks with a new baby, so please
re-ping him if there is no response soon.
--
Michael
-----Original Message-----
From: Patrick J. LoPresti [mailto:patl at users.sourceforge.net]
Sent: Friday, February 27, 2004 2:30 PM
To: Brown, Michael E
Cc: hpa at zytor.com; syslinux at zytor.com
Subject: Re: [syslinux] BIOS disk geometry and Linux 2.6
Michael_E_Brown at Dell.com writes:
> Just do the int13 calls in setup.S and save the results in
> empty-zero-page. Make the data available via sys/proc.
OK, below is my initial attempt at a patch.
It creates new nodes under /sys/firmware/edd/int13_devXX named
legacy_cylinders, legacy_heads, and legacy_sectors. The values within are
the maximum cylinder number, maximum head number, and maximum sector number
as returned by the legacy INT13/AH=08h "get drive parameters" call
(http://www.ctyme.com/intr/rb-0621.htm).
In general, I tried to follow the coding style already present. But I make
no claims about the quality of my code, especially the assembly portion.
It works on my test systems, so I am good to go. Thank you for the help,
Michael and Peter!
Note that these files hold the literal values returned by the BIOS. If I
understand correctly, you have to add 1 to "legacy_heads" before the value
is useful (i.e., before you set it as the bios_head value in
/proc/sys/.../settings). We could do that arithmetic here, but I think it
is cleaner to worry about it in userspace.
Michael, you may want to ask Matt to push this change or something like it
through to the Linux folks.
- Pat
diff -u -r linux-2.6.3-orig/arch/i386/boot/setup.S
linux-2.6.3/arch/i386/boot/setup.S
--- linux-2.6.3-orig/arch/i386/boot/setup.S 2004-02-17
22:58:11.000000000 -0500
+++ linux-2.6.3/arch/i386/boot/setup.S 2004-02-27 14:58:46.000000000 -0500
@@ -650,6 +650,31 @@
int $0x13 # make the call
# Don't check for fail
return
# it doesn't matter.
+edd_get_legacy_chs:
+ xorw %ax, %ax
+ movw %ax, %ds:-8(%si)
+ movw %ax, %ds:-6(%si)
+ # Ralf Brown's Interrupt List says to set ES:DI to
+ # 0000h:0000h "to guard against BIOS bugs"
+ pushw %es
+ movw %ax, %es
+ movw %ax, %di
+ pushw %dx # legacy call clobbers %dl
+ movb $LEGACYGETDEVICEPARAMETERS, %ah # Function 08
+ int $0x13 # make the call
+ popw %es
+ jc edd_legacy_done # failed
+ movb %cl, %al # Low 6 bits are max
+ andb $0x3F, %al # sector number
+ movb %al, %ds:-5(%si) # Record max sect
+ movb %dh, %ds:-6(%si) # Record max head number
+ movb %ch, %al # Low 8 bits of max cyl
+ shr $6, %cl
+ movb %cl, %ah # High 2 bits of max cyl
+ movw %ax, %ds:-8(%si)
+
+edd_legacy_done:
+ popw %dx
movw %si, %ax # increment si
addw $EDDPARMSIZE+EDDEXTSIZE, %ax
movw %ax, %si
diff -u -r linux-2.6.3-orig/arch/i386/kernel/edd.c
linux-2.6.3/arch/i386/kernel/edd.c
--- linux-2.6.3-orig/arch/i386/kernel/edd.c 2004-02-17
22:57:22.000000000 -0500
+++ linux-2.6.3/arch/i386/kernel/edd.c 2004-02-27 14:22:12.000000000 -0500
@@ -321,6 +321,45 @@
}
static ssize_t
+edd_show_legacy_cylinders(struct edd_device *edev, char *buf) {
+ struct edd_info *info = edd_dev_get_info(edev);
+ char *p = buf;
+ if (!edev || !info || !buf) {
+ return -EINVAL;
+ }
+
+ p += snprintf(p, left, "0x%x\n", info->legacy_cylinders);
+ return (p - buf);
+}
+
+static ssize_t
+edd_show_legacy_heads(struct edd_device *edev, char *buf)
+{
+ struct edd_info *info = edd_dev_get_info(edev);
+ char *p = buf;
+ if (!edev || !info || !buf) {
+ return -EINVAL;
+ }
+
+ p += snprintf(p, left, "0x%x\n", info->legacy_heads);
+ return (p - buf);
+}
+
+static ssize_t
+edd_show_legacy_sectors(struct edd_device *edev, char *buf)
+{
+ struct edd_info *info = edd_dev_get_info(edev);
+ char *p = buf;
+ if (!edev || !info || !buf) {
+ return -EINVAL;
+ }
+
+ p += snprintf(p, left, "0x%x\n", info->legacy_sectors);
+ return (p - buf);
+}
+
+static ssize_t
edd_show_default_cylinders(struct edd_device *edev, char *buf) {
struct edd_info *info = edd_dev_get_info(edev);
@@ -384,6 +423,33 @@
*/
static int
+edd_has_legacy_cylinders(struct edd_device *edev)
+{
+ struct edd_info *info = edd_dev_get_info(edev);
+ if (!edev || !info)
+ return -EINVAL;
+ return info->legacy_cylinders > 0;
+}
+
+static int
+edd_has_legacy_heads(struct edd_device *edev)
+{
+ struct edd_info *info = edd_dev_get_info(edev);
+ if (!edev || !info)
+ return -EINVAL;
+ return info->legacy_heads > 0;
+}
+
+static int
+edd_has_legacy_sectors(struct edd_device *edev)
+{
+ struct edd_info *info = edd_dev_get_info(edev);
+ if (!edev || !info)
+ return -EINVAL;
+ return info->legacy_sectors > 0;
+}
+
+static int
edd_has_default_cylinders(struct edd_device *edev)
{
struct edd_info *info = edd_dev_get_info(edev);
@@ -452,6 +518,12 @@
static EDD_DEVICE_ATTR(extensions, 0444, edd_show_extensions, NULL);
static EDD_DEVICE_ATTR(info_flags, 0444, edd_show_info_flags, NULL); static
EDD_DEVICE_ATTR(sectors, 0444, edd_show_sectors, NULL);
+static EDD_DEVICE_ATTR(legacy_cylinders, 0444, edd_show_legacy_cylinders,
+ edd_has_legacy_cylinders);
+static EDD_DEVICE_ATTR(legacy_heads, 0444, edd_show_legacy_heads,
+ edd_has_legacy_heads);
+static EDD_DEVICE_ATTR(legacy_sectors, 0444, edd_show_legacy_sectors,
+ edd_has_legacy_sectors);
static EDD_DEVICE_ATTR(default_cylinders, 0444, edd_show_default_cylinders,
edd_has_default_cylinders);
static EDD_DEVICE_ATTR(default_heads, 0444, edd_show_default_heads, @@
-478,6 +550,9 @@
/* These attributes are conditional and only added for some devices. */
static struct edd_attribute * edd_attrs[] = {
+ &edd_attr_legacy_cylinders,
+ &edd_attr_legacy_heads,
+ &edd_attr_legacy_sectors,
&edd_attr_default_cylinders,
&edd_attr_default_heads,
&edd_attr_default_sectors_per_track,
diff -u -r linux-2.6.3-orig/include/asm-i386/edd.h
linux-2.6.3/include/asm-i386/edd.h
--- linux-2.6.3-orig/include/asm-i386/edd.h 2004-02-17
22:57:12.000000000 -0500
+++ linux-2.6.3/include/asm-i386/edd.h 2004-02-27 14:21:01.000000000 -0500
@@ -34,10 +34,11 @@
in empty_zero_block - treat this as 1
byte */
#define EDDBUF 0x600 /* addr of edd_info structs in
empty_zero_block */
#define EDDMAXNR 6 /* number of edd_info structs starting at
EDDBUF */
-#define EDDEXTSIZE 4 /* change these if you muck with the
structures */
+#define EDDEXTSIZE 8 /* change these if you muck with the
structures */
#define EDDPARMSIZE 74
#define CHECKEXTENSIONSPRESENT 0x41
#define GETDEVICEPARAMETERS 0x48
+#define LEGACYGETDEVICEPARAMETERS 0x08
#define EDDMAGIC1 0x55AA
#define EDDMAGIC2 0xAA55
@@ -162,6 +163,9 @@
} __attribute__ ((packed));
struct edd_info {
+ u16 legacy_cylinders;
+ u8 legacy_heads;
+ u8 legacy_sectors;
u8 device;
u8 version;
u16 interface_support;
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