1 // SPDX-License-Identifier: GPL-2.0
3  * scsicam.c - SCSI CAM support functions, use for HDIO_GETGEO, etc.
7  *      (Unix and Linux consulting and custom programming)
9  *      +1 (303) 786-7975
11  * For more information, please consult the SCSI-CAM draft.
26  * scsi_bios_ptable - Read PC partition table out of first sector of device.
35 	struct address_space *mapping = dev->bd_contains->bd_inode->i_mapping;  in scsi_bios_ptable()
51  * scsi_partsize - Parse cylinders/heads/sectors from PC partition table
74 		int largest_cyl = -1, i;  in scsi_partsize()
77 			if (!p->sys_ind)  in scsi_partsize()
83 			cyl = p->cyl + ((p->sector & 0xc0) << 2);  in scsi_partsize()
91 		end_cyl = largest->end_cyl + ((largest->end_sector & 0xc0) << 2);  in scsi_partsize()
92 		end_head = largest->end_head;  in scsi_partsize()
93 		end_sector = largest->end_sector & 0x3f;  in scsi_partsize()
107 		logical_end = get_unaligned_le32(&largest->start_sect)  in scsi_partsize()
108 		    + get_unaligned_le32(&largest->nr_sects);  in scsi_partsize()
111 		ext_cyl = (logical_end - (end_head * end_sector + end_sector))  in scsi_partsize()
146  * Purpose : to determine a near-optimal int 0x13 mapping for a
150  * Returns : -1 on failure, 0 on success.
156  * see http://www.t10.org/ftp/t10/drafts/cam/cam-r12b.pdf
159  *                                                         10-MAR-94
160  * Information technology -
161  * SCSI-2 Common access method
167  * head-cylinder-sector requirements. It minimizes the value for
180 	unsigned long heads, sectors, cylinders, temp;  in setsize()  local
185 	temp = cylinders * sectors;	/* Compute divisor for heads */  in setsize()
186 	heads = capacity / temp;	/* Compute value for number of heads */  in setsize()
187 	if (capacity % temp) {	/* If no remainder, done! */  in setsize()
189 		temp = cylinders * heads;	/* Compute divisor for sectors */  in setsize()
190 		sectors = capacity / temp;	/* Compute value for sectors per  in setsize()
192 		if (capacity % temp) {	/* If no remainder, done! */  in setsize()
194 			temp = heads * sectors;		/* Compute divisor for cylinders */  in setsize()
195 			cylinders = capacity / temp;	/* Compute number of cylinders */  in setsize()
199 		rv = (unsigned) -1;	/* Give error if 0 cylinders */  in setsize()
208  * scsicam_bios_param - Determine geometry of a disk in cylinders/heads/sectors.
214  *      SCSI-CAM system, storing the results in ip as required
217  * Returns : -1 on failure, 0 on success.
231 		 * at most 62 sectors per track - this works up to 7905 MB.  in scsicam_bios_param()