patch-2.3.99-pre1 linux/drivers/ide/hd.c

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diff -u --recursive --new-file v2.3.51/linux/drivers/ide/hd.c linux/drivers/ide/hd.c
@@ -0,0 +1,883 @@
+/*
+ *  linux/drivers/block/hd.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+/*
+ * This is the low-level hd interrupt support. It traverses the
+ * request-list, using interrupts to jump between functions. As
+ * all the functions are called within interrupts, we may not
+ * sleep. Special care is recommended.
+ * 
+ *  modified by Drew Eckhardt to check nr of hd's from the CMOS.
+ *
+ *  Thanks to Branko Lankester, lankeste@fwi.uva.nl, who found a bug
+ *  in the early extended-partition checks and added DM partitions
+ *
+ *  IRQ-unmask, drive-id, multiple-mode, support for ">16 heads",
+ *  and general streamlining by Mark Lord.
+ *
+ *  Removed 99% of above. Use Mark's ide driver for those options.
+ *  This is now a lightweight ST-506 driver. (Paul Gortmaker)
+ *
+ *  Modified 1995 Russell King for ARM processor.
+ */
+  
+/* Uncomment the following if you want verbose error reports. */
+/* #define VERBOSE_ERRORS */
+  
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/fs.h>
+#include <linux/devfs_fs_kernel.h>
+#include <linux/kernel.h>
+#include <linux/hdreg.h>
+#include <linux/genhd.h>
+#include <linux/malloc.h>
+#include <linux/string.h>
+#include <linux/ioport.h>
+#include <linux/mc146818rtc.h> /* CMOS defines */
+#include <linux/init.h>
+#include <linux/blkpg.h>
+
+#define REALLY_SLOW_IO
+#include <asm/system.h>
+#include <asm/io.h>
+#include <asm/uaccess.h>
+
+#define MAJOR_NR HD_MAJOR
+#include <linux/blk.h>
+
+#ifdef __arm__
+#undef  HD_IRQ
+#endif
+#include <asm/irq.h>
+#ifdef __arm__
+#define HD_IRQ IRQ_HARDDISK
+#endif
+
+static int revalidate_hddisk(kdev_t, int);
+
+#define	HD_DELAY	0
+
+#define MAX_ERRORS     16	/* Max read/write errors/sector */
+#define RESET_FREQ      8	/* Reset controller every 8th retry */
+#define RECAL_FREQ      4	/* Recalibrate every 4th retry */
+#define MAX_HD		2
+
+#define STAT_OK		(READY_STAT|SEEK_STAT)
+#define OK_STATUS(s)	(((s)&(STAT_OK|(BUSY_STAT|WRERR_STAT|ERR_STAT)))==STAT_OK)
+
+static void recal_intr(void);
+static void bad_rw_intr(void);
+
+static char recalibrate[MAX_HD];
+static char special_op[MAX_HD];
+static int access_count[MAX_HD];
+static char busy[MAX_HD];
+static DECLARE_WAIT_QUEUE_HEAD(busy_wait);
+
+static int reset;
+static int hd_error;
+
+#define SUBSECTOR(block) (CURRENT->current_nr_sectors > 0)
+
+/*
+ *  This struct defines the HD's and their types.
+ */
+struct hd_i_struct {
+	unsigned int head,sect,cyl,wpcom,lzone,ctl;
+};
+	
+#ifdef HD_TYPE
+static struct hd_i_struct hd_info[] = { HD_TYPE };
+static int NR_HD = ((sizeof (hd_info))/(sizeof (struct hd_i_struct)));
+#else
+static struct hd_i_struct hd_info[MAX_HD];
+static int NR_HD;
+#endif
+
+static struct hd_struct hd[MAX_HD<<6];
+static int hd_sizes[MAX_HD<<6];
+static int hd_blocksizes[MAX_HD<<6];
+static int hd_hardsectsizes[MAX_HD<<6];
+
+#if (HD_DELAY > 0)
+unsigned long last_req;
+
+unsigned long read_timer(void)
+{
+	unsigned long t, flags;
+	int i;
+
+	save_flags(flags);
+	cli();
+	t = jiffies * 11932;
+    	outb_p(0, 0x43);
+	i = inb_p(0x40);
+	i |= inb(0x40) << 8;
+	restore_flags(flags);
+	return(t - i);
+}
+#endif
+
+void __init hd_setup(char *str, int *ints)
+{
+	int hdind = 0;
+
+	if (ints[0] != 3)
+		return;
+	if (hd_info[0].head != 0)
+		hdind=1;
+	hd_info[hdind].head = ints[2];
+	hd_info[hdind].sect = ints[3];
+	hd_info[hdind].cyl = ints[1];
+	hd_info[hdind].wpcom = 0;
+	hd_info[hdind].lzone = ints[1];
+	hd_info[hdind].ctl = (ints[2] > 8 ? 8 : 0);
+	NR_HD = hdind+1;
+}
+
+static void dump_status (const char *msg, unsigned int stat)
+{
+	unsigned long flags;
+	char devc;
+
+	devc = !QUEUE_EMPTY ? 'a' + DEVICE_NR(CURRENT->rq_dev) : '?';
+	save_flags (flags);
+	sti();
+#ifdef VERBOSE_ERRORS
+	printk("hd%c: %s: status=0x%02x { ", devc, msg, stat & 0xff);
+	if (stat & BUSY_STAT)	printk("Busy ");
+	if (stat & READY_STAT)	printk("DriveReady ");
+	if (stat & WRERR_STAT)	printk("WriteFault ");
+	if (stat & SEEK_STAT)	printk("SeekComplete ");
+	if (stat & DRQ_STAT)	printk("DataRequest ");
+	if (stat & ECC_STAT)	printk("CorrectedError ");
+	if (stat & INDEX_STAT)	printk("Index ");
+	if (stat & ERR_STAT)	printk("Error ");
+	printk("}\n");
+	if ((stat & ERR_STAT) == 0) {
+		hd_error = 0;
+	} else {
+		hd_error = inb(HD_ERROR);
+		printk("hd%c: %s: error=0x%02x { ", devc, msg, hd_error & 0xff);
+		if (hd_error & BBD_ERR)		printk("BadSector ");
+		if (hd_error & ECC_ERR)		printk("UncorrectableError ");
+		if (hd_error & ID_ERR)		printk("SectorIdNotFound ");
+		if (hd_error & ABRT_ERR)	printk("DriveStatusError ");
+		if (hd_error & TRK0_ERR)	printk("TrackZeroNotFound ");
+		if (hd_error & MARK_ERR)	printk("AddrMarkNotFound ");
+		printk("}");
+		if (hd_error & (BBD_ERR|ECC_ERR|ID_ERR|MARK_ERR)) {
+			printk(", CHS=%d/%d/%d", (inb(HD_HCYL)<<8) + inb(HD_LCYL),
+				inb(HD_CURRENT) & 0xf, inb(HD_SECTOR));
+			if (!QUEUE_EMPTY)
+				printk(", sector=%ld", CURRENT->sector);
+		}
+		printk("\n");
+	}
+#else
+	printk("hd%c: %s: status=0x%02x.\n", devc, msg, stat & 0xff);
+	if ((stat & ERR_STAT) == 0) {
+		hd_error = 0;
+	} else {
+		hd_error = inb(HD_ERROR);
+		printk("hd%c: %s: error=0x%02x.\n", devc, msg, hd_error & 0xff);
+	}
+#endif	/* verbose errors */
+	restore_flags (flags);
+}
+
+void check_status(void)
+{
+	int i = inb_p(HD_STATUS);
+
+	if (!OK_STATUS(i)) {
+		dump_status("check_status", i);
+		bad_rw_intr();
+	}
+}
+
+static int controller_busy(void)
+{
+	int retries = 100000;
+	unsigned char status;
+
+	do {
+		status = inb_p(HD_STATUS);
+	} while ((status & BUSY_STAT) && --retries);
+	return status;
+}
+
+static int status_ok(void)
+{
+	unsigned char status = inb_p(HD_STATUS);
+
+	if (status & BUSY_STAT)
+		return 1;	/* Ancient, but does it make sense??? */
+	if (status & WRERR_STAT)
+		return 0;
+	if (!(status & READY_STAT))
+		return 0;
+	if (!(status & SEEK_STAT))
+		return 0;
+	return 1;
+}
+
+static int controller_ready(unsigned int drive, unsigned int head)
+{
+	int retry = 100;
+
+	do {
+		if (controller_busy() & BUSY_STAT)
+			return 0;
+		outb_p(0xA0 | (drive<<4) | head, HD_CURRENT);
+		if (status_ok())
+			return 1;
+	} while (--retry);
+	return 0;
+}
+
+static void hd_out(unsigned int drive,unsigned int nsect,unsigned int sect,
+		unsigned int head,unsigned int cyl,unsigned int cmd,
+		void (*intr_addr)(void))
+{
+	unsigned short port;
+
+#if (HD_DELAY > 0)
+	while (read_timer() - last_req < HD_DELAY)
+		/* nothing */;
+#endif
+	if (reset)
+		return;
+	if (!controller_ready(drive, head)) {
+		reset = 1;
+		return;
+	}
+	SET_INTR(intr_addr);
+	outb_p(hd_info[drive].ctl,HD_CMD);
+	port=HD_DATA;
+	outb_p(hd_info[drive].wpcom>>2,++port);
+	outb_p(nsect,++port);
+	outb_p(sect,++port);
+	outb_p(cyl,++port);
+	outb_p(cyl>>8,++port);
+	outb_p(0xA0|(drive<<4)|head,++port);
+	outb_p(cmd,++port);
+}
+
+static void hd_request (void);
+
+static int drive_busy(void)
+{
+	unsigned int i;
+	unsigned char c;
+
+	for (i = 0; i < 500000 ; i++) {
+		c = inb_p(HD_STATUS);
+		if ((c & (BUSY_STAT | READY_STAT | SEEK_STAT)) == STAT_OK)
+			return 0;
+	}
+	dump_status("reset timed out", c);
+	return 1;
+}
+
+static void reset_controller(void)
+{
+	int	i;
+
+	outb_p(4,HD_CMD);
+	for(i = 0; i < 1000; i++) barrier();
+	outb_p(hd_info[0].ctl & 0x0f,HD_CMD);
+	for(i = 0; i < 1000; i++) barrier();
+	if (drive_busy())
+		printk("hd: controller still busy\n");
+	else if ((hd_error = inb(HD_ERROR)) != 1)
+		printk("hd: controller reset failed: %02x\n",hd_error);
+}
+
+static void reset_hd(void)
+{
+	static int i;
+
+repeat:
+	if (reset) {
+		reset = 0;
+		i = -1;
+		reset_controller();
+	} else {
+		check_status();
+		if (reset)
+			goto repeat;
+	}
+	if (++i < NR_HD) {
+		special_op[i] = recalibrate[i] = 1;
+		hd_out(i,hd_info[i].sect,hd_info[i].sect,hd_info[i].head-1,
+			hd_info[i].cyl,WIN_SPECIFY,&reset_hd);
+		if (reset)
+			goto repeat;
+	} else
+		hd_request();
+}
+
+/*
+ * Ok, don't know what to do with the unexpected interrupts: on some machines
+ * doing a reset and a retry seems to result in an eternal loop. Right now I
+ * ignore it, and just set the timeout.
+ *
+ * On laptops (and "green" PCs), an unexpected interrupt occurs whenever the
+ * drive enters "idle", "standby", or "sleep" mode, so if the status looks
+ * "good", we just ignore the interrupt completely.
+ */
+void unexpected_hd_interrupt(void)
+{
+	unsigned int stat = inb_p(HD_STATUS);
+
+	if (stat & (BUSY_STAT|DRQ_STAT|ECC_STAT|ERR_STAT)) {
+		dump_status ("unexpected interrupt", stat);
+		SET_TIMER;
+	}
+}
+
+/*
+ * bad_rw_intr() now tries to be a bit smarter and does things
+ * according to the error returned by the controller.
+ * -Mika Liljeberg (liljeber@cs.Helsinki.FI)
+ */
+static void bad_rw_intr(void)
+{
+	int dev;
+
+	if (QUEUE_EMPTY)
+		return;
+	dev = DEVICE_NR(CURRENT->rq_dev);
+	if (++CURRENT->errors >= MAX_ERRORS || (hd_error & BBD_ERR)) {
+		end_request(0);
+		special_op[dev] = recalibrate[dev] = 1;
+	} else if (CURRENT->errors % RESET_FREQ == 0)
+		reset = 1;
+	else if ((hd_error & TRK0_ERR) || CURRENT->errors % RECAL_FREQ == 0)
+		special_op[dev] = recalibrate[dev] = 1;
+	/* Otherwise just retry */
+}
+
+static inline int wait_DRQ(void)
+{
+	int retries = 100000, stat;
+
+	while (--retries > 0)
+		if ((stat = inb_p(HD_STATUS)) & DRQ_STAT)
+			return 0;
+	dump_status("wait_DRQ", stat);
+	return -1;
+}
+
+static void read_intr(void)
+{
+	int i, retries = 100000;
+
+	do {
+		i = (unsigned) inb_p(HD_STATUS);
+		if (i & BUSY_STAT)
+			continue;
+		if (!OK_STATUS(i))
+			break;
+		if (i & DRQ_STAT)
+			goto ok_to_read;
+	} while (--retries > 0);
+	dump_status("read_intr", i);
+	bad_rw_intr();
+	hd_request();
+	return;
+ok_to_read:
+	insw(HD_DATA,CURRENT->buffer,256);
+	CURRENT->sector++;
+	CURRENT->buffer += 512;
+	CURRENT->errors = 0;
+	i = --CURRENT->nr_sectors;
+	--CURRENT->current_nr_sectors;
+#ifdef DEBUG
+	printk("hd%c: read: sector %ld, remaining = %ld, buffer=0x%08lx\n",
+		dev+'a', CURRENT->sector, CURRENT->nr_sectors,
+		(unsigned long) CURRENT->buffer+512));
+#endif
+	if (CURRENT->current_nr_sectors <= 0)
+		end_request(1);
+	if (i > 0) {
+		SET_INTR(&read_intr);
+		return;
+	}
+	(void) inb_p(HD_STATUS);
+#if (HD_DELAY > 0)
+	last_req = read_timer();
+#endif
+	if (!QUEUE_EMPTY)
+		hd_request();
+	return;
+}
+
+static void write_intr(void)
+{
+	int i;
+	int retries = 100000;
+
+	do {
+		i = (unsigned) inb_p(HD_STATUS);
+		if (i & BUSY_STAT)
+			continue;
+		if (!OK_STATUS(i))
+			break;
+		if ((CURRENT->nr_sectors <= 1) || (i & DRQ_STAT))
+			goto ok_to_write;
+	} while (--retries > 0);
+	dump_status("write_intr", i);
+	bad_rw_intr();
+	hd_request();
+	return;
+ok_to_write:
+	CURRENT->sector++;
+	i = --CURRENT->nr_sectors;
+	--CURRENT->current_nr_sectors;
+	CURRENT->buffer += 512;
+	if (!i || (CURRENT->bh && !SUBSECTOR(i)))
+		end_request(1);
+	if (i > 0) {
+		SET_INTR(&write_intr);
+		outsw(HD_DATA,CURRENT->buffer,256);
+		sti();
+	} else {
+#if (HD_DELAY > 0)
+		last_req = read_timer();
+#endif
+		hd_request();
+	}
+	return;
+}
+
+static void recal_intr(void)
+{
+	check_status();
+#if (HD_DELAY > 0)
+	last_req = read_timer();
+#endif
+	hd_request();
+}
+
+/*
+ * This is another of the error-routines I don't know what to do with. The
+ * best idea seems to just set reset, and start all over again.
+ */
+static void hd_times_out(void)
+{
+	unsigned int dev;
+
+	DEVICE_INTR = NULL;
+	if (QUEUE_EMPTY)
+		return;
+	disable_irq(HD_IRQ);
+	sti();
+	reset = 1;
+	dev = DEVICE_NR(CURRENT->rq_dev);
+	printk("hd%c: timeout\n", dev+'a');
+	if (++CURRENT->errors >= MAX_ERRORS) {
+#ifdef DEBUG
+		printk("hd%c: too many errors\n", dev+'a');
+#endif
+		end_request(0);
+	}
+	cli();
+	hd_request();
+	enable_irq(HD_IRQ);
+}
+
+int do_special_op (unsigned int dev)
+{
+	if (recalibrate[dev]) {
+		recalibrate[dev] = 0;
+		hd_out(dev,hd_info[dev].sect,0,0,0,WIN_RESTORE,&recal_intr);
+		return reset;
+	}
+	if (hd_info[dev].head > 16) {
+		printk ("hd%c: cannot handle device with more than 16 heads - giving up\n", dev+'a');
+		end_request(0);
+	}
+	special_op[dev] = 0;
+	return 1;
+}
+
+/*
+ * The driver enables interrupts as much as possible.  In order to do this,
+ * (a) the device-interrupt is disabled before entering hd_request(),
+ * and (b) the timeout-interrupt is disabled before the sti().
+ *
+ * Interrupts are still masked (by default) whenever we are exchanging
+ * data/cmds with a drive, because some drives seem to have very poor
+ * tolerance for latency during I/O. The IDE driver has support to unmask
+ * interrupts for non-broken hardware, so use that driver if required.
+ */
+static void hd_request(void)
+{
+	unsigned int dev, block, nsect, sec, track, head, cyl;
+
+	if (!QUEUE_EMPTY && CURRENT->rq_status == RQ_INACTIVE) return;
+	if (DEVICE_INTR)
+		return;
+repeat:
+	timer_active &= ~(1<<HD_TIMER);
+	sti();
+	INIT_REQUEST;
+	if (reset) {
+		cli();
+		reset_hd();
+		return;
+	}
+	dev = MINOR(CURRENT->rq_dev);
+	block = CURRENT->sector;
+	nsect = CURRENT->nr_sectors;
+	if (dev >= (NR_HD<<6) || block >= hd[dev].nr_sects || ((block+nsect) > hd[dev].nr_sects)) {
+#ifdef DEBUG
+		if (dev >= (NR_HD<<6))
+			printk("hd: bad minor number: device=%s\n",
+			       kdevname(CURRENT->rq_dev));
+		else
+			printk("hd%c: bad access: block=%d, count=%d\n",
+				(MINOR(CURRENT->rq_dev)>>6)+'a', block, nsect);
+#endif
+		end_request(0);
+		goto repeat;
+	}
+	block += hd[dev].start_sect;
+	dev >>= 6;
+	if (special_op[dev]) {
+		if (do_special_op(dev))
+			goto repeat;
+		return;
+	}
+	sec   = block % hd_info[dev].sect + 1;
+	track = block / hd_info[dev].sect;
+	head  = track % hd_info[dev].head;
+	cyl   = track / hd_info[dev].head;
+#ifdef DEBUG
+	printk("hd%c: %sing: CHS=%d/%d/%d, sectors=%d, buffer=0x%08lx\n",
+		dev+'a', (CURRENT->cmd == READ)?"read":"writ",
+		cyl, head, sec, nsect, (unsigned long) CURRENT->buffer);
+#endif
+	if (CURRENT->cmd == READ) {
+		hd_out(dev,nsect,sec,head,cyl,WIN_READ,&read_intr);
+		if (reset)
+			goto repeat;
+		return;
+	}
+	if (CURRENT->cmd == WRITE) {
+		hd_out(dev,nsect,sec,head,cyl,WIN_WRITE,&write_intr);
+		if (reset)
+			goto repeat;
+		if (wait_DRQ()) {
+			bad_rw_intr();
+			goto repeat;
+		}
+		outsw(HD_DATA,CURRENT->buffer,256);
+		return;
+	}
+	panic("unknown hd-command");
+}
+
+static void do_hd_request (request_queue_t * q)
+{
+	disable_irq(HD_IRQ);
+	hd_request();
+	enable_irq(HD_IRQ);
+}
+
+static int hd_ioctl(struct inode * inode, struct file * file,
+	unsigned int cmd, unsigned long arg)
+{
+	struct hd_geometry *loc = (struct hd_geometry *) arg;
+	int dev;
+
+	if ((!inode) || !(inode->i_rdev))
+		return -EINVAL;
+	dev = DEVICE_NR(inode->i_rdev);
+	if (dev >= NR_HD)
+		return -EINVAL;
+	switch (cmd) {
+		case HDIO_GETGEO:
+		{
+			struct hd_geometry g; 
+			if (!loc)  return -EINVAL;
+			g.heads = hd_info[dev].head;
+			g.sectors = hd_info[dev].sect;
+			g.cylinders = hd_info[dev].cyl;
+			g.start = hd[MINOR(inode->i_rdev)].start_sect;
+			return copy_to_user(loc, &g, sizeof g) ? -EFAULT : 0; 
+		}
+
+         	case BLKGETSIZE:   /* Return device size */
+			if (!arg)  return -EINVAL;
+			return put_user(hd[MINOR(inode->i_rdev)].nr_sects, 
+					(long *) arg);
+
+		case BLKRRPART: /* Re-read partition tables */
+			if (!capable(CAP_SYS_ADMIN))
+				return -EACCES;
+			return revalidate_hddisk(inode->i_rdev, 1);
+
+		case BLKROSET:
+		case BLKROGET:
+		case BLKRASET:
+		case BLKRAGET:
+		case BLKFLSBUF:
+		case BLKPG:
+			return blk_ioctl(inode->i_rdev, cmd, arg);
+
+		default:
+			return -EINVAL;
+	}
+}
+
+static int hd_open(struct inode * inode, struct file * filp)
+{
+	int target;
+	target =  DEVICE_NR(inode->i_rdev);
+
+	if (target >= NR_HD)
+		return -ENODEV;
+	while (busy[target])
+		sleep_on(&busy_wait);
+	access_count[target]++;
+	return 0;
+}
+
+/*
+ * Releasing a block device means we sync() it, so that it can safely
+ * be forgotten about...
+ */
+static int hd_release(struct inode * inode, struct file * file)
+{
+        int target =  DEVICE_NR(inode->i_rdev);
+	access_count[target]--;
+	return 0;
+}
+
+extern struct block_device_operations hd_fops;
+
+static struct gendisk hd_gendisk = {
+	MAJOR_NR,	/* Major number */	
+	"hd",		/* Major name */
+	6,		/* Bits to shift to get real from partition */
+	1 << 6,		/* Number of partitions per real */
+	hd,		/* hd struct */
+	hd_sizes,	/* block sizes */
+	0,		/* number */
+	NULL,		/* internal use, not presently used */
+	NULL,		/* next */
+	&hd_fops,       /* file operations */
+};
+	
+static void hd_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+	void (*handler)(void) = DEVICE_INTR;
+
+	DEVICE_INTR = NULL;
+	timer_active &= ~(1<<HD_TIMER);
+	if (!handler)
+		handler = unexpected_hd_interrupt;
+	handler();
+	sti();
+}
+
+static struct block_device_operations hd_fops = {
+	open:		hd_open,
+	release:	hd_release,
+	ioctl:		hd_ioctl,
+};
+
+/*
+ * This is the hard disk IRQ description. The SA_INTERRUPT in sa_flags
+ * means we run the IRQ-handler with interrupts disabled:  this is bad for
+ * interrupt latency, but anything else has led to problems on some
+ * machines.
+ *
+ * We enable interrupts in some of the routines after making sure it's
+ * safe.
+ */
+static void hd_geninit(void)
+{
+	int drive;
+
+	for(drive=0; drive < (MAX_HD << 6); drive++) {
+		hd_blocksizes[drive] = 1024;
+		hd_hardsectsizes[drive] = 512;
+	}
+	blksize_size[MAJOR_NR] = hd_blocksizes;
+	hardsect_size[MAJOR_NR] = hd_hardsectsizes;
+
+#ifdef __i386__
+	if (!NR_HD) {
+		extern struct drive_info drive_info;
+		unsigned char *BIOS = (unsigned char *) &drive_info;
+		int cmos_disks;
+
+		for (drive=0 ; drive<2 ; drive++) {
+			hd_info[drive].cyl = *(unsigned short *) BIOS;
+			hd_info[drive].head = *(2+BIOS);
+			hd_info[drive].wpcom = *(unsigned short *) (5+BIOS);
+			hd_info[drive].ctl = *(8+BIOS);
+			hd_info[drive].lzone = *(unsigned short *) (12+BIOS);
+			hd_info[drive].sect = *(14+BIOS);
+#ifdef does_not_work_for_everybody_with_scsi_but_helps_ibm_vp
+			if (hd_info[drive].cyl && NR_HD == drive)
+				NR_HD++;
+#endif
+			BIOS += 16;
+		}
+
+	/*
+		We query CMOS about hard disks : it could be that 
+		we have a SCSI/ESDI/etc controller that is BIOS
+		compatible with ST-506, and thus showing up in our
+		BIOS table, but not register compatible, and therefore
+		not present in CMOS.
+
+		Furthermore, we will assume that our ST-506 drives
+		<if any> are the primary drives in the system, and 
+		the ones reflected as drive 1 or 2.
+
+		The first drive is stored in the high nibble of CMOS
+		byte 0x12, the second in the low nibble.  This will be
+		either a 4 bit drive type or 0xf indicating use byte 0x19 
+		for an 8 bit type, drive 1, 0x1a for drive 2 in CMOS.
+
+		Needless to say, a non-zero value means we have 
+		an AT controller hard disk for that drive.
+
+		
+	*/
+
+		if ((cmos_disks = CMOS_READ(0x12)) & 0xf0) {
+			if (cmos_disks & 0x0f)
+				NR_HD = 2;
+			else
+				NR_HD = 1;
+		}
+	}
+#endif /* __i386__ */
+#ifdef __arm__
+	if (!NR_HD) {
+		/* We don't know anything about the drive.  This means
+		 * that you *MUST* specify the drive parameters to the
+		 * kernel yourself.
+		 */
+		printk("hd: no drives specified - use hd=cyl,head,sectors"
+			" on kernel command line\n");
+	}
+#endif
+
+	for (drive=0 ; drive < NR_HD ; drive++) {
+		printk ("hd%c: %ldMB, CHS=%d/%d/%d\n", drive+'a',
+			hd[drive<<6].nr_sects / 2048, hd_info[drive].cyl,
+			hd_info[drive].head, hd_info[drive].sect);
+	}
+	if (!NR_HD)
+		return;
+
+	if (request_irq(HD_IRQ, hd_interrupt, SA_INTERRUPT, "hd", NULL)) {
+		printk("hd: unable to get IRQ%d for the hard disk driver\n",
+			HD_IRQ);
+		NR_HD = 0;
+		return;
+	}
+	request_region(HD_DATA, 8, "hd");
+	request_region(HD_CMD, 1, "hd(cmd)");
+
+	hd_gendisk.nr_real = NR_HD;
+
+	for(drive=0; drive < NR_HD; drive++)
+		register_disk(&hd_gendisk, MKDEV(MAJOR_NR,drive<<6), 1<<6,
+			&hd_fops, hd_info[drive].head * hd_info[drive].sect *
+			hd_info[drive].cyl);
+}
+
+int __init hd_init(void)
+{
+	if (devfs_register_blkdev(MAJOR_NR,"hd",&hd_fops)) {
+		printk("hd: unable to get major %d for hard disk\n",MAJOR_NR);
+		return -1;
+	}
+	blk_init_queue(BLK_DEFAULT_QUEUE(MAJOR_NR), DEVICE_REQUEST);
+	read_ahead[MAJOR_NR] = 8;		/* 8 sector (4kB) read-ahead */
+	hd_gendisk.next = gendisk_head;
+	gendisk_head = &hd_gendisk;
+	timer_table[HD_TIMER].fn = hd_times_out;
+	hd_geninit();
+	return 0;
+}
+
+#define DEVICE_BUSY busy[target]
+#define USAGE access_count[target]
+#define CAPACITY (hd_info[target].head*hd_info[target].sect*hd_info[target].cyl)
+/* We assume that the BIOS parameters do not change, so the disk capacity
+   will not change */
+#undef MAYBE_REINIT
+#define GENDISK_STRUCT hd_gendisk
+
+/*
+ * This routine is called to flush all partitions and partition tables
+ * for a changed disk, and then re-read the new partition table.
+ * If we are revalidating a disk because of a media change, then we
+ * enter with usage == 0.  If we are using an ioctl, we automatically have
+ * usage == 1 (we need an open channel to use an ioctl :-), so this
+ * is our limit.
+ */
+static int revalidate_hddisk(kdev_t dev, int maxusage)
+{
+	int target;
+	struct gendisk * gdev;
+	int max_p;
+	int start;
+	int i;
+	long flags;
+
+	target = DEVICE_NR(dev);
+	gdev = &GENDISK_STRUCT;
+
+	save_flags(flags);
+	cli();
+	if (DEVICE_BUSY || USAGE > maxusage) {
+		restore_flags(flags);
+		return -EBUSY;
+	}
+	DEVICE_BUSY = 1;
+	restore_flags(flags);
+
+	max_p = gdev->max_p;
+	start = target << gdev->minor_shift;
+
+	for (i=max_p - 1; i >=0 ; i--) {
+		int minor = start + i;
+		kdev_t devi = MKDEV(MAJOR_NR, minor);
+		struct super_block *sb = get_super(devi); 
+
+		sync_dev(devi);
+		if (sb)
+			invalidate_inodes(sb);
+		invalidate_buffers(devi);
+		gdev->part[minor].start_sect = 0;
+		gdev->part[minor].nr_sects = 0;
+	}
+
+#ifdef MAYBE_REINIT
+	MAYBE_REINIT;
+#endif
+
+	grok_partitions(gdev, target, 1<<6, CAPACITY);
+
+	DEVICE_BUSY = 0;
+	wake_up(&busy_wait);
+	return 0;
+}
+
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)