diff options
Diffstat (limited to 'drivers/scsi/scsicam.c')
| -rw-r--r-- | drivers/scsi/scsicam.c | 257 |
1 files changed, 257 insertions, 0 deletions
diff --git a/drivers/scsi/scsicam.c b/drivers/scsi/scsicam.c new file mode 100644 index 000000000..e2c7d8ef2 --- /dev/null +++ b/drivers/scsi/scsicam.c @@ -0,0 +1,257 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * 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/kernel.h> +#include <linux/blkdev.h> +#include <linux/pagemap.h> +#include <linux/msdos_partition.h> +#include <asm/unaligned.h> + +#include <scsi/scsicam.h> + +/** + * 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) +{ + struct address_space *mapping = bdev_whole(dev)->bd_inode->i_mapping; + unsigned char *res = NULL; + struct folio *folio; + + folio = read_mapping_folio(mapping, 0, NULL); + if (IS_ERR(folio)) + return NULL; + + res = kmemdup(folio_address(folio) + 0x1be, 66, GFP_KERNEL); + folio_put(folio); + return res; +} +EXPORT_SYMBOL(scsi_bios_ptable); + +/** + * scsi_partsize - Parse cylinders/heads/sectors from PC partition table + * @bdev: block device to parse + * @capacity: size of the disk in sectors + * @geom: output in form of [hds, cylinders, sectors] + * + * Determine the BIOS mapping/geometry used to create the partition + * table, storing the results in @geom. + * + * Returns: %false on failure, %true on success. + */ +bool scsi_partsize(struct block_device *bdev, sector_t capacity, int geom[3]) +{ + int cyl, ext_cyl, end_head, end_cyl, end_sector; + unsigned int logical_end, physical_end, ext_physical_end; + struct msdos_partition *p, *largest = NULL; + void *buf; + int ret = false; + + buf = scsi_bios_ptable(bdev); + if (!buf) + return false; + + if (*(unsigned short *) (buf + 64) == 0xAA55) { + int largest_cyl = -1, i; + + for (i = 0, p = buf; 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) + goto out_free_buf; + +#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)) { + geom[0] = end_head + 1; + geom[1] = end_sector; + geom[2] = (unsigned long)capacity / + ((end_head + 1) * end_sector); + ret = true; + goto out_free_buf; + } +#ifdef DEBUG + printk("scsicam_bios_param : logical (%u) != physical (%u)\n", + logical_end, physical_end); +#endif + } + +out_free_buf: + kfree(buf); + return ret; +} +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); +} + +/** + * 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) +{ + u64 capacity64 = capacity; /* Suppress gcc warning */ + int ret = 0; + + /* try to infer mapping from partition table */ + if (scsi_partsize(bdev, capacity, ip)) + return 0; + + if (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); |