--- /dev/null
+/*
+ * scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc.
+ *
+ * Copyright 1993, 1994 Drew Eckhardt
+ * Visionary Computing
+ * (Unix and Linux consulting and custom programming)
+ * drew@Colorado.EDU
+ * +1 (303) 786-7975
+ *
+ * For more information, please consult the SCSI-CAM draft.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/genhd.h>
+#include <linux/kernel.h>
+#include <linux/blkdev.h>
+#include <asm/unaligned.h>
+
+#include <scsi/scsicam.h>
+
+
+static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
+ unsigned int *secs);
+
+/**
+ * scsi_bios_ptable - Read PC partition table out of first sector of device.
+ * @dev: from this device
+ *
+ * Description: Reads the first sector from the device and returns %0x42 bytes
+ * starting at offset %0x1be.
+ * Returns: partition table in kmalloc(GFP_KERNEL) memory, or NULL on error.
+ */
+unsigned char *scsi_bios_ptable(struct block_device *dev)
+{
+ unsigned char *res = kmalloc(66, GFP_KERNEL);
+ if (res) {
+ struct block_device *bdev = dev->bd_contains;
+ Sector sect;
+ void *data = read_dev_sector(bdev, 0, §);
+ if (data) {
+ memcpy(res, data + 0x1be, 66);
+ put_dev_sector(sect);
+ } else {
+ kfree(res);
+ res = NULL;
+ }
+ }
+ return res;
+}
+EXPORT_SYMBOL(scsi_bios_ptable);
+
+/**
+ * scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors.
+ * @bdev: which device
+ * @capacity: size of the disk in sectors
+ * @ip: return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders
+ *
+ * Description : determine the BIOS mapping/geometry used for a drive in a
+ * SCSI-CAM system, storing the results in ip as required
+ * by the HDIO_GETGEO ioctl().
+ *
+ * Returns : -1 on failure, 0 on success.
+ */
+
+int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip)
+{
+ unsigned char *p;
+ u64 capacity64 = capacity; /* Suppress gcc warning */
+ int ret;
+
+ p = scsi_bios_ptable(bdev);
+ if (!p)
+ return -1;
+
+ /* try to infer mapping from partition table */
+ ret = scsi_partsize(p, (unsigned long)capacity, (unsigned int *)ip + 2,
+ (unsigned int *)ip + 0, (unsigned int *)ip + 1);
+ kfree(p);
+
+ if (ret == -1 && capacity64 < (1ULL << 32)) {
+ /* pick some standard mapping with at most 1024 cylinders,
+ and at most 62 sectors per track - this works up to
+ 7905 MB */
+ ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2,
+ (unsigned int *)ip + 0, (unsigned int *)ip + 1);
+ }
+
+ /* if something went wrong, then apparently we have to return
+ a geometry with more than 1024 cylinders */
+ if (ret || ip[0] > 255 || ip[1] > 63) {
+ if ((capacity >> 11) > 65534) {
+ ip[0] = 255;
+ ip[1] = 63;
+ } else {
+ ip[0] = 64;
+ ip[1] = 32;
+ }
+
+ if (capacity > 65535*63*255)
+ ip[2] = 65535;
+ else
+ ip[2] = (unsigned long)capacity / (ip[0] * ip[1]);
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(scsicam_bios_param);
+
+/**
+ * scsi_partsize - Parse cylinders/heads/sectors from PC partition table
+ * @buf: partition table, see scsi_bios_ptable()
+ * @capacity: size of the disk in sectors
+ * @cyls: put cylinders here
+ * @hds: put heads here
+ * @secs: put sectors here
+ *
+ * Description: determine the BIOS mapping/geometry used to create the partition
+ * table, storing the results in *cyls, *hds, and *secs
+ *
+ * Returns: -1 on failure, 0 on success.
+ */
+
+int scsi_partsize(unsigned char *buf, unsigned long capacity,
+ unsigned int *cyls, unsigned int *hds, unsigned int *secs)
+{
+ struct partition *p = (struct partition *)buf, *largest = NULL;
+ int i, largest_cyl;
+ int cyl, ext_cyl, end_head, end_cyl, end_sector;
+ unsigned int logical_end, physical_end, ext_physical_end;
+
+
+ if (*(unsigned short *) (buf + 64) == 0xAA55) {
+ for (largest_cyl = -1, i = 0; i < 4; ++i, ++p) {
+ if (!p->sys_ind)
+ continue;
+#ifdef DEBUG
+ printk("scsicam_bios_param : partition %d has system \n",
+ i);
+#endif
+ cyl = p->cyl + ((p->sector & 0xc0) << 2);
+ if (cyl > largest_cyl) {
+ largest_cyl = cyl;
+ largest = p;
+ }
+ }
+ }
+ if (largest) {
+ end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);
+ end_head = largest->end_head;
+ end_sector = largest->end_sector & 0x3f;
+
+ if (end_head + 1 == 0 || end_sector == 0)
+ return -1;
+
+#ifdef DEBUG
+ printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n",
+ end_head, end_cyl, end_sector);
+#endif
+
+ physical_end = end_cyl * (end_head + 1) * end_sector +
+ end_head * end_sector + end_sector;
+
+ /* This is the actual _sector_ number at the end */
+ logical_end = get_unaligned_le32(&largest->start_sect)
+ + get_unaligned_le32(&largest->nr_sects);
+
+ /* This is for >1023 cylinders */
+ ext_cyl = (logical_end - (end_head * end_sector + end_sector))
+ / (end_head + 1) / end_sector;
+ ext_physical_end = ext_cyl * (end_head + 1) * end_sector +
+ end_head * end_sector + end_sector;
+
+#ifdef DEBUG
+ printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n"
+ ,logical_end, physical_end, ext_physical_end, ext_cyl);
+#endif
+
+ if ((logical_end == physical_end) ||
+ (end_cyl == 1023 && ext_physical_end == logical_end)) {
+ *secs = end_sector;
+ *hds = end_head + 1;
+ *cyls = capacity / ((end_head + 1) * end_sector);
+ return 0;
+ }
+#ifdef DEBUG
+ printk("scsicam_bios_param : logical (%u) != physical (%u)\n",
+ logical_end, physical_end);
+#endif
+ }
+ return -1;
+}
+EXPORT_SYMBOL(scsi_partsize);
+
+/*
+ * Function : static int setsize(unsigned long capacity,unsigned int *cyls,
+ * unsigned int *hds, unsigned int *secs);
+ *
+ * Purpose : to determine a near-optimal int 0x13 mapping for a
+ * SCSI disk in terms of lost space of size capacity, storing
+ * the results in *cyls, *hds, and *secs.
+ *
+ * Returns : -1 on failure, 0 on success.
+ *
+ * Extracted from
+ *
+ * WORKING X3T9.2
+ * DRAFT 792D
+ * see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf
+ *
+ * Revision 6
+ * 10-MAR-94
+ * Information technology -
+ * SCSI-2 Common access method
+ * transport and SCSI interface module
+ *
+ * ANNEX A :
+ *
+ * setsize() converts a read capacity value to int 13h
+ * head-cylinder-sector requirements. It minimizes the value for
+ * number of heads and maximizes the number of cylinders. This
+ * will support rather large disks before the number of heads
+ * will not fit in 4 bits (or 6 bits). This algorithm also
+ * minimizes the number of sectors that will be unused at the end
+ * of the disk while allowing for very large disks to be
+ * accommodated. This algorithm does not use physical geometry.
+ */
+
+static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds,
+ unsigned int *secs)
+{
+ unsigned int rv = 0;
+ unsigned long heads, sectors, cylinders, temp;
+
+ cylinders = 1024L; /* Set number of cylinders to max */
+ sectors = 62L; /* Maximize sectors per track */
+
+ temp = cylinders * sectors; /* Compute divisor for heads */
+ heads = capacity / temp; /* Compute value for number of heads */
+ if (capacity % temp) { /* If no remainder, done! */
+ heads++; /* Else, increment number of heads */
+ temp = cylinders * heads; /* Compute divisor for sectors */
+ sectors = capacity / temp; /* Compute value for sectors per
+ track */
+ if (capacity % temp) { /* If no remainder, done! */
+ sectors++; /* Else, increment number of sectors */
+ temp = heads * sectors; /* Compute divisor for cylinders */
+ cylinders = capacity / temp; /* Compute number of cylinders */
+ }
+ }
+ if (cylinders == 0)
+ rv = (unsigned) -1; /* Give error if 0 cylinders */
+
+ *cyls = (unsigned int) cylinders; /* Stuff return values */
+ *secs = (unsigned int) sectors;
+ *hds = (unsigned int) heads;
+ return (rv);
+}
Code Review / kvmfornfv.git / blobdiff