AT91RM9200-ide.rar_9200 usb_IDE接口_at91rm9200_at91rm9200 ide_ide

/* * linux/drivers/ide/ide-tape.c Version 1.17a Jan, 2001 * * Copyright (C) 1995 - 1999 Gadi Oxman <gadio@netvision.net.il> * * $Header$ * * This driver was constructed as a student project in the software laboratory * of the faculty of electrical engineering in the Technion - Israel's * Institute Of Technology, with the guide of Avner Lottem and Dr. Ilana David. * * It is hereby placed under the terms of the GNU general public license. * (See linux/COPYING). */ /* * IDE ATAPI streaming tape driver. * * This driver is a part of the Linux ide driver and works in co-operation * with linux/drivers/block/ide.c. * * The driver, in co-operation with ide.c, basically traverses the * request-list for the block device interface. The character device * interface, on the other hand, creates new requests, adds them * to the request-list of the block device, and waits for their completion. * * Pipelined operation mode is now supported on both reads and writes. * * The block device major and minor numbers are determined from the * tape's relative position in the ide interfaces, as explained in ide.c. * * The character device interface consists of the following devices: * * ht0 major 37, minor 0 first IDE tape, rewind on close. * ht1 major 37, minor 1 second IDE tape, rewind on close. * ... * nht0 major 37, minor 128 first IDE tape, no rewind on close. * nht1 major 37, minor 129 second IDE tape, no rewind on close. * ... * * Run linux/scripts/MAKEDEV.ide to create the above entries. * * The general magnetic tape commands compatible interface, as defined by * include/linux/mtio.h, is accessible through the character device. * * General ide driver configuration options, such as the interrupt-unmask * flag, can be configured by issuing an ioctl to the block device interface, * as any other ide device. * * Our own ide-tape ioctl's can be issued to either the block device or * the character device interface. * * Maximal throughput with minimal bus load will usually be achieved in the * following scenario: * * 1. ide-tape is operating in the pipelined operation mode. * 2. No buffering is performed by the user backup program. * * Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive. * * Ver 0.1 Nov 1 95 Pre-working code :-) * Ver 0.2 Nov 23 95 A short backup (few megabytes) and restore procedure * was successful ! (Using tar cvf ... on the block * device interface). * A longer backup resulted in major swapping, bad * overall Linux performance and eventually failed as * we received non serial read-ahead requests from the * buffer cache. * Ver 0.3 Nov 28 95 Long backups are now possible, thanks to the * character device interface. Linux's responsiveness * and performance doesn't seem to be much affected * from the background backup procedure. * Some general mtio.h magnetic tape operations are * now supported by our character device. As a result, * popular tape utilities are starting to work with * ide tapes :-) * The following configurations were tested: * 1. An IDE ATAPI TAPE shares the same interface * and irq with an IDE ATAPI CDROM. * 2. An IDE ATAPI TAPE shares the same interface * and irq with a normal IDE disk. * Both configurations seemed to work just fine ! * However, to be on the safe side, it is meanwhile * recommended to give the IDE TAPE its own interface * and irq. * The one thing which needs to be done here is to * add a "request postpone" feature to ide.c, * so that we won't have to wait for the tape to finish * performing a long media access (DSC) request (such * as a rewind) before we can access the other device * on the same interface. This effect doesn't disturb * normal operation most of the time because read/write * requests are relatively fast, and once we are * performing one tape r/w request, a lot of requests * from the other device can be queued and ide.c will * service all of them after this single tape request. * Ver 1.0 Dec 11 95 Integrated into Linux 1.3.46 development tree. * On each read / write request, we now ask the drive * if we can transfer a constant number of bytes * (a parameter of the drive) only to its buffers, * without causing actual media access. If we can't, * we just wait until we can by polling the DSC bit. * This ensures that while we are not transferring * more bytes than the constant referred to above, the * interrupt latency will not become too high and * we won't cause an interrupt timeout, as happened * occasionally in the previous version. * While polling for DSC, the current request is * postponed and ide.c is free to handle requests from * the other device. This is handled transparently to * ide.c. The hwgroup locking method which was used * in the previous version was removed. * Use of new general features which are provided by * ide.c for use with atapi devices. * (Programming done by Mark Lord) * Few potential bug fixes (Again, suggested by Mark) * Single character device data transfers are now * not limited in size, as they were before. * We are asking the tape about its recommended * transfer unit and send a larger data transfer * as several transfers of the above size. * For best results, use an integral number of this * basic unit (which is shown during driver * initialization). I will soon add an ioctl to get * this important parameter. * Our data transfer buffer is allocated on startup, * rather than before each data transfer. This should * ensure that we will indeed have a data buffer. * Ver 1.1 Dec 14 95 Fixed random problems which occurred when the tape * shared an interface with another device. * (poll_for_dsc was a complete mess). * Removed some old (non-active) code which had * to do with supporting buffer cache originated * requests. * The block device interface can now be opened, so * that general ide driver features like the unmask * interrupts flag can be selected with an ioctl. * This is the only use of the block device interface. * New fast pipelined operation mode (currently only on * writes). When using the pipelined mode, the * throughput can potentially reach the maximum * tape supporte