VxWorks 下PCI 驱动编程

/* dosPartLibAta.c - show & mount ATA HDD MSDOS partitions */ /* modification history -------------------- 01c,15sep97,jkf removed LCHS support. Only useful for MSDOS versions before 3.3, not likely anyone needs LCHS support. Added support for big endian arches and arches without dynamic bus sizing, which involved byte swapping macro and reading sector data with macro offsets. Now supports 80x86, 68k, SPARC, MIPS, PPC, i960, etc.) Revised docs. 01b,01sep97,jkf fixed check for LBA support in dosPartRdLbaAta(). fixed stdlib.h filename case for Unix. fixed args to ataDevCreate in example comments. fixed cosmetics in sector and show routines. 01a,01sep97,jkf written. */ /* DESCRIPTION: This library is provided by Wind River Systems Customer Support strictly as an educational example. This code supports both mounting and displaying partition tables written by MSDOS FDISK.exe or by any other MSDOS FDISK.exe compatible partitioning software. The first partition table is contained within a hard drives Master Boot Record (MBR) sector, which is defined as sector one, cylinder zero, head zero or logical block address zero. The mounting and displaying routines within this code will first parse the MBR partition tables entries (defined below) and also recursively parse any "extended" partition tables, which may reside within another Cylinder, Head, and Sector (CHS) combination further into the hard disk. (Also known as extended partition tables chained from the MBR's partition table. MSDOS file systems within extended partitions are known to those familiar with the MSDOS FDISK.exe utility as "Logical drives within the extended partition". Since MSDOS file systems have a fixed number of clusters, 64Kb, and clusters are the minimum allocation unit at the file system level, using partitions can help optimize cluster size for a given hard disk, improving performance and resource usage. For example, a 1-gigabyte hard disk with a single MSDOS file system has the following minimum allocation unit at the dosFsLib open/read/write level interface: 1GB/64KB = Minimum allocation unit. This may produce a minimum allocation unit that is larger than what the developer desires (for cluster boundary buffer alignment, or other buffering, ect). One solution is to sub-divide the disk into smaller partitions or "logical disks" on the single physical disk and format file systems over each of the partitions. (Then using this code you may mount them.) If you used four equal sized partitions, then this method produces: 256MB/64KB = Minimum allocation unit. 256MB/64KB = Minimum allocation unit. 256MB/64KB = Minimum allocation unit. 256MB/64KB = Minimum allocation unit. This produces a smaller minimum allocation unit and may be better suited for optimal application file system performance. Each partition contains its own unique file system. As far as the file system level is concerned it is on a unique disk. Here is a picture showing the layout of a single disk containing multiple MSDOS file systems: (Note, all ASCII pictures herein are best viewed with an 'equally sized characters' or 'fixed width' style font) +---------------------------------------------------------+ |<---------------------The entire disk------------------->| |M | |B<---C:---> | |R /---- First extended partition--------------\| | E<---D:---><-Rest of the ext part------------>| |P x | |A t E<---E:--->E<Rest of the ext part->| |R x x | |T t t<---------F:---------->| +---------------------------------------------------------+ (Ext == extended partition sector) A MS-DOS partition table resides within one sector on a hard disk. There is always one in the first sector of a hard disk partitioned with FDISK.exe. There first partition table may contain references to "extended" partition tables residing on other sectors if there are multiple partitions. The first sector of the disk is the starting point. Partition tables are of the format: Offset from the beginning of the sector Description ------------- ------------------------- 0x1be Partition 1 table entry (16 bytes) 0x1ce Partition 2 table entry (16 bytes) 0x1de Partition 3 table entry (16 bytes) 0x1ee Partition 4 table entry (16 bytes) 0x1fe Signature (0x55aa, 2 bytes) Individual MSDOS partition table entries are of the format: Offset Size Description ------ ---- ------------------------------ 0x0 8 bits boot type 0x1 8 bits beginning sector head value 0x2 8 bits beginning sector (2 high bits of cylinder#) 0x3 8 bits beginning cylinder# (low order bits of cylinder#) 0x4 8 bits system indicator 0x5 8 bits ending sector head value 0x6 8 bits ending sector (2 high bits of cylinder#) 0x7 8 bits ending cylinder# (low order bits of cylinder#) 0x8 32 bits number of sectors preceding the partition 0xc 32 bits number of sectors in the partition In the partition table entry, the Sector/Cylinder (16bits) (offset 0x2 & 0x3) fields data are stored in the format: |7|6|5|4|3|2|1|0| The first 8 bits of offset 0x2. | | `------------ 6 least significant bit's contain the sector | | offset within cylinder. sector == 6 bits. | | `-`-------------- Two most significant (high order) bits of the cylinder value. |7|6|5|4|3|2|1|0| 2nd 8 bits (cylinder 0x3) `---------------- Eight least significant (low order) bits of the cylinder value. This format restricts partition entries to 10 cylinder bits & 6 sector bits and 8 head bits. This is also the format used by the PC-AT BIOS Int13h functions, which is used by FDISK.exe dosPartLibAta/Scsi.c uses the following method of parsing the CHS values stored in the 0x2 & 0x3 partition table offsets into distinct values: Cyl = ((((dospt_startSec) & 0x00c0) << 2) | (((dospt_startSec) & 0xff00) >> 8)); Hd = pPartTbl->dospt_startHead; Sec = (pPartTbl->dospt_startSec & 0x003f); (see DOS_PART_TBL struct typedef in dosFsLib.h) This produces individual CHS value from the values that are contained within the MSDOS partition table entry. Definitions of CHS terms: CHS - Cylinder/Head/Sector. L-CHS - Logical - CHS (used by INT 13 AxH/FDISK.exe) 256 heads, 1024 cylinders, 63 sectors. max. LCHS allow ~8.4 GB addressable space. P-CHS - Physical CHS (used by physical ATA device) 16 heads, 65535 cylinders, 63 sectors. PCHS allow ~137GB addressable space. (VxWorks ataRawio() uses PCHS) LBA - Logical Block Address. ATA/SCSI absolute sector numbering scheme. LBA sector 0 == addresses the first sector on a device by definition. ATA devices may also support LBA at the device interface. ATA standard says that cylinder 0, head 0, sector 1 == LBA 0. LBA allows (~137GB) on an ATA device. The MSDOS "logical CHS" (LCHS) format combined with the Physical IDE/ATA CHS interface (PCHS) gives MSDOS the following addressing limitation: +------------+----------+----------------+ | BIOS INT13 | IDE/ATA | Combined Limit | +-----------------+------------+----------+----------------+ |Max Sectors/Track| 63 | 255 | 63 | +-----------------+------------+----------+----------------+ |Max Heads | 256 | 16 | 16 | +--