[block] Replace gPXE block-device API with an iPXE asynchronous interface

The block device interface used in gPXE predates the invention of even
the old gPXE data-transfer interface, let alone the current iPXE
generic asynchronous interface mechanism.  Bring this old code up to
date, with the following benefits:

 o  Block device commands can be cancelled by the requestor.  The INT 13
    layer uses this to provide a global timeout on all INT 13 calls,
    with the result that an unexpected passive failure mode (such as
    an iSCSI target ACKing the request but never sending a response)
    will lead to a timeout that gets reported back to the INT 13 user,
    rather than simply freezing the system.

 o  INT 13,00 (reset drive) is now able to reset the underlying block
    device.  INT 13 users, such as DOS, that use INT 13,00 as a method
    for error recovery now have a chance of recovering.

 o  All block device commands are tagged, with a numerical tag that
    will show up in debugging output and in packet captures; this will
    allow easier interpretation of bug reports that include both
    sources of information.

 o  The extremely ugly hacks used to generate the boot firmware tables
    have been eradicated and replaced with a generic acpi_describe()
    method (exploiting the ability of iPXE interfaces to pass through
    methods to an underlying interface).  The ACPI tables are now
    built in a shared data block within .bss16, rather than each
    requiring dedicated space in .data16.

 o  The architecture-independent concept of a SAN device has been
    exposed to the iPXE core through the sanboot API, which provides
    calls to hook, unhook, boot, and describe SAN devices.  This
    allows for much more flexible usage patterns (such as hooking an
    empty SAN device and then running an OS installer via TFTP).

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/include/int13.h

@@ -13,8 +13,6 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <ipxe/list.h>
 #include <realmode.h>
 
-struct block_device;
-
 /**
  * @defgroup int13ops INT 13 operation codes
  * @{
@@ -56,6 +54,8 @@ struct block_device;
 #define INT13_STATUS_INVALID		0x01
 /** Read error */
 #define INT13_STATUS_READ_ERROR		0x04
+/** Reset failed */
+#define INT13_STATUS_RESET_FAILED	0x05
 /** Write error */
 #define INT13_STATUS_WRITE_ERROR	0xcc
 
@@ -64,57 +64,6 @@ struct block_device;
 /** Block size for non-extended INT 13 calls */
 #define INT13_BLKSIZE 512
 
-/** An INT 13 emulated drive */
-struct int13_drive {
-	/** List of all registered drives */
-	struct list_head list;
-
-	/** Underlying block device */
-	struct block_device *blockdev;
-
-	/** BIOS in-use drive number (0x80-0xff) */
-	unsigned int drive;
-	/** BIOS natural drive number (0x80-0xff)
-	 *
-	 * This is the drive number that would have been assigned by
-	 * 'naturally' appending the drive to the end of the BIOS
-	 * drive list.
-	 *
-	 * If the emulated drive replaces a preexisting drive, this is
-	 * the drive number that the preexisting drive gets remapped
-	 * to.
-	 */
-	unsigned int natural_drive;
-
-	/** Number of cylinders
-	 *
-	 * The cylinder number field in an INT 13 call is ten bits
-	 * wide, giving a maximum of 1024 cylinders.  Conventionally,
-	 * when the 7.8GB limit of a CHS address is exceeded, it is
-	 * the number of cylinders that is increased beyond the
-	 * addressable limit.
-	 */
-	unsigned int cylinders;
-	/** Number of heads
-	 *
-	 * The head number field in an INT 13 call is eight bits wide,
-	 * giving a maximum of 256 heads.  However, apparently all
-	 * versions of MS-DOS up to and including Win95 fail with 256
-	 * heads, so the maximum encountered in practice is 255.
-	 */
-	unsigned int heads;
-	/** Number of sectors per track
-	 *
-	 * The sector number field in an INT 13 call is six bits wide,
-	 * giving a maximum of 63 sectors, since sector numbering
-	 * (unlike head and cylinder numbering) starts at 1, not 0.
-	 */
-	unsigned int sectors_per_track;
-
-	/** Status of last operation */
-	int last_status;
-};
-
 /** An INT 13 disk address packet */
 struct int13_disk_address {
 	/** Size of the packet, in bytes */
@@ -147,7 +96,6 @@ struct int13_disk_parameters {
 	uint64_t sectors;
 	/** Bytes per sector */
 	uint16_t sector_size;
-	
 } __attribute__ (( packed ));
 
 /**
@@ -285,8 +233,7 @@ struct master_boot_record {
 	uint16_t signature;
 } __attribute__ (( packed ));
 
-extern void register_int13_drive ( struct int13_drive *drive );
-extern void unregister_int13_drive ( struct int13_drive *drive );
-extern int int13_boot ( unsigned int drive );
+/** Use natural BIOS drive number */
+#define INT13_USE_NATURAL_DRIVE 0xff
 
 #endif /* INT13_H */