/* * 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 #include #include #include #include #include #include #include #include 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(&largest->start_sect) + get_unaligned(&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); }