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259 lines
7.6 KiB
259 lines
7.6 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc. |
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* |
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* Copyright 1993, 1994 Drew Eckhardt |
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* Visionary Computing |
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* (Unix and Linux consulting and custom programming) |
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* [email protected] |
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* +1 (303) 786-7975 |
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* |
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* For more information, please consult the SCSI-CAM draft. |
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*/ |
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#include <linux/module.h> |
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#include <linux/slab.h> |
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#include <linux/fs.h> |
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#include <linux/genhd.h> |
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#include <linux/kernel.h> |
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#include <linux/blkdev.h> |
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#include <linux/pagemap.h> |
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#include <linux/msdos_partition.h> |
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#include <asm/unaligned.h> |
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#include <scsi/scsicam.h> |
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/** |
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* scsi_bios_ptable - Read PC partition table out of first sector of device. |
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* @dev: from this device |
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* |
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* Description: Reads the first sector from the device and returns %0x42 bytes |
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* starting at offset %0x1be. |
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* Returns: partition table in kmalloc(GFP_KERNEL) memory, or NULL on error. |
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*/ |
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unsigned char *scsi_bios_ptable(struct block_device *dev) |
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{ |
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struct address_space *mapping = bdev_whole(dev)->bd_inode->i_mapping; |
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unsigned char *res = NULL; |
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struct page *page; |
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page = read_mapping_page(mapping, 0, NULL); |
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if (IS_ERR(page)) |
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return NULL; |
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if (!PageError(page)) |
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res = kmemdup(page_address(page) + 0x1be, 66, GFP_KERNEL); |
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put_page(page); |
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return res; |
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} |
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EXPORT_SYMBOL(scsi_bios_ptable); |
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/** |
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* scsi_partsize - Parse cylinders/heads/sectors from PC partition table |
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* @bdev: block device to parse |
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* @capacity: size of the disk in sectors |
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* @geom: output in form of [hds, cylinders, sectors] |
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* |
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* Determine the BIOS mapping/geometry used to create the partition |
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* table, storing the results in @geom. |
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* |
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* Returns: %false on failure, %true on success. |
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*/ |
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bool scsi_partsize(struct block_device *bdev, sector_t capacity, int geom[3]) |
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{ |
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int cyl, ext_cyl, end_head, end_cyl, end_sector; |
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unsigned int logical_end, physical_end, ext_physical_end; |
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struct msdos_partition *p, *largest = NULL; |
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void *buf; |
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int ret = false; |
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buf = scsi_bios_ptable(bdev); |
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if (!buf) |
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return false; |
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if (*(unsigned short *) (buf + 64) == 0xAA55) { |
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int largest_cyl = -1, i; |
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for (i = 0, p = buf; i < 4; i++, p++) { |
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if (!p->sys_ind) |
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continue; |
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#ifdef DEBUG |
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printk("scsicam_bios_param : partition %d has system \n", |
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i); |
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#endif |
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cyl = p->cyl + ((p->sector & 0xc0) << 2); |
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if (cyl > largest_cyl) { |
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largest_cyl = cyl; |
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largest = p; |
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} |
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} |
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} |
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if (largest) { |
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end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2); |
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end_head = largest->end_head; |
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end_sector = largest->end_sector & 0x3f; |
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if (end_head + 1 == 0 || end_sector == 0) |
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goto out_free_buf; |
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#ifdef DEBUG |
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printk("scsicam_bios_param : end at h = %d, c = %d, s = %d\n", |
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end_head, end_cyl, end_sector); |
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#endif |
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physical_end = end_cyl * (end_head + 1) * end_sector + |
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end_head * end_sector + end_sector; |
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/* This is the actual _sector_ number at the end */ |
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logical_end = get_unaligned_le32(&largest->start_sect) |
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+ get_unaligned_le32(&largest->nr_sects); |
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/* This is for >1023 cylinders */ |
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ext_cyl = (logical_end - (end_head * end_sector + end_sector)) |
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/ (end_head + 1) / end_sector; |
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ext_physical_end = ext_cyl * (end_head + 1) * end_sector + |
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end_head * end_sector + end_sector; |
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#ifdef DEBUG |
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printk("scsicam_bios_param : logical_end=%d physical_end=%d ext_physical_end=%d ext_cyl=%d\n" |
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,logical_end, physical_end, ext_physical_end, ext_cyl); |
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#endif |
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if (logical_end == physical_end || |
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(end_cyl == 1023 && ext_physical_end == logical_end)) { |
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geom[0] = end_head + 1; |
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geom[1] = end_sector; |
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geom[2] = (unsigned long)capacity / |
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((end_head + 1) * end_sector); |
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ret = true; |
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goto out_free_buf; |
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} |
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#ifdef DEBUG |
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printk("scsicam_bios_param : logical (%u) != physical (%u)\n", |
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logical_end, physical_end); |
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#endif |
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} |
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out_free_buf: |
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kfree(buf); |
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return ret; |
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} |
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EXPORT_SYMBOL(scsi_partsize); |
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/* |
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* Function : static int setsize(unsigned long capacity,unsigned int *cyls, |
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* unsigned int *hds, unsigned int *secs); |
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* |
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* Purpose : to determine a near-optimal int 0x13 mapping for a |
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* SCSI disk in terms of lost space of size capacity, storing |
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* the results in *cyls, *hds, and *secs. |
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* |
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* Returns : -1 on failure, 0 on success. |
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* |
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* Extracted from |
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* |
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* WORKING X3T9.2 |
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* DRAFT 792D |
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* see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf |
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* |
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* Revision 6 |
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* 10-MAR-94 |
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* Information technology - |
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* SCSI-2 Common access method |
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* transport and SCSI interface module |
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* |
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* ANNEX A : |
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* |
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* setsize() converts a read capacity value to int 13h |
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* head-cylinder-sector requirements. It minimizes the value for |
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* number of heads and maximizes the number of cylinders. This |
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* will support rather large disks before the number of heads |
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* will not fit in 4 bits (or 6 bits). This algorithm also |
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* minimizes the number of sectors that will be unused at the end |
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* of the disk while allowing for very large disks to be |
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* accommodated. This algorithm does not use physical geometry. |
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*/ |
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static int setsize(unsigned long capacity, unsigned int *cyls, unsigned int *hds, |
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unsigned int *secs) |
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{ |
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unsigned int rv = 0; |
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unsigned long heads, sectors, cylinders, temp; |
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cylinders = 1024L; /* Set number of cylinders to max */ |
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sectors = 62L; /* Maximize sectors per track */ |
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temp = cylinders * sectors; /* Compute divisor for heads */ |
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heads = capacity / temp; /* Compute value for number of heads */ |
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if (capacity % temp) { /* If no remainder, done! */ |
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heads++; /* Else, increment number of heads */ |
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temp = cylinders * heads; /* Compute divisor for sectors */ |
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sectors = capacity / temp; /* Compute value for sectors per |
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track */ |
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if (capacity % temp) { /* If no remainder, done! */ |
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sectors++; /* Else, increment number of sectors */ |
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temp = heads * sectors; /* Compute divisor for cylinders */ |
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cylinders = capacity / temp; /* Compute number of cylinders */ |
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} |
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} |
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if (cylinders == 0) |
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rv = (unsigned) -1; /* Give error if 0 cylinders */ |
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*cyls = (unsigned int) cylinders; /* Stuff return values */ |
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*secs = (unsigned int) sectors; |
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*hds = (unsigned int) heads; |
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return (rv); |
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} |
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/** |
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* scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors. |
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* @bdev: which device |
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* @capacity: size of the disk in sectors |
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* @ip: return value: ip[0]=heads, ip[1]=sectors, ip[2]=cylinders |
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* |
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* Description : determine the BIOS mapping/geometry used for a drive in a |
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* SCSI-CAM system, storing the results in ip as required |
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* by the HDIO_GETGEO ioctl(). |
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* |
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* Returns : -1 on failure, 0 on success. |
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*/ |
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int scsicam_bios_param(struct block_device *bdev, sector_t capacity, int *ip) |
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{ |
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u64 capacity64 = capacity; /* Suppress gcc warning */ |
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int ret = 0; |
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/* try to infer mapping from partition table */ |
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if (scsi_partsize(bdev, capacity, ip)) |
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return 0; |
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if (capacity64 < (1ULL << 32)) { |
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/* |
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* Pick some standard mapping with at most 1024 cylinders, and |
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* at most 62 sectors per track - this works up to 7905 MB. |
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*/ |
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ret = setsize((unsigned long)capacity, (unsigned int *)ip + 2, |
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(unsigned int *)ip + 0, (unsigned int *)ip + 1); |
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} |
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/* |
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* If something went wrong, then apparently we have to return a geometry |
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* with more than 1024 cylinders. |
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*/ |
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if (ret || ip[0] > 255 || ip[1] > 63) { |
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if ((capacity >> 11) > 65534) { |
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ip[0] = 255; |
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ip[1] = 63; |
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} else { |
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ip[0] = 64; |
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ip[1] = 32; |
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} |
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if (capacity > 65535*63*255) |
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ip[2] = 65535; |
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else |
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ip[2] = (unsigned long)capacity / (ip[0] * ip[1]); |
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} |
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return 0; |
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} |
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EXPORT_SYMBOL(scsicam_bios_param);
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