drivers/scsi/scsicam.c

Source file repositories/reference/linux-study-clean/drivers/scsi/scsicam.c

File Facts

System
Linux kernel
Corpus path
drivers/scsi/scsicam.c
Extension
.c
Size
7728 bytes
Lines
258
Domain
Driver Families
Bucket
drivers/scsi
Inferred role
Driver Families: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

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.

Annotation

Implementation Notes