scsi.c

讲述linux的初始化过程

/*
 *  scsi.c Copyright (C) 1992 Drew Eckhardt
 *         Copyright (C) 1993, 1994, 1995, 1999 Eric Youngdale
 *
 *  generic mid-level SCSI driver
 *      Initial versions: Drew Eckhardt
 *      Subsequent revisions: Eric Youngdale
 *
 *  <[e-mail]>
 *
 *  Bug correction thanks go to :
 *      Rik Faith <[e-mail]>
 *      Tommy Thorn <tthorn>
 *      Thomas Wuensche <[e-mail]>
 *
 *  Modified by Eric Youngdale [e-mail] or [e-mail] to
 *  add scatter-gather, multiple outstanding request, and other
 *  enhancements.
 *
 *  Native multichannel, wide scsi, /proc/scsi and hot plugging
 *  support added by Michael Neuffer <[e-mail]>
 *
 *  Added request_module("scsi_hostadapter") for kerneld:
 *  (Put an "alias scsi_hostadapter your_hostadapter" in /etc/modules.conf)
 *  Bjorn Ekwall  <[e-mail]>
 *  (changed to kmod)
 *
 *  Major improvements to the timeout, abort, and reset processing,
 *  as well as performance modifications for large queue depths by
 *  Leonard N. Zubkoff <[e-mail]>
 *
 *  Converted cli() code to spinlocks, Ingo Molnar
 *
 *  Jiffies wrap fixes (host->resetting), 3 Dec 1998 Andrea Arcangeli
 *
 *  out_of_space hacks, D. Gilbert (dpg) 990608
 */

#define REVISION	"Revision: 1.00"
#define VERSION		"Id: scsi.c 1.00 2000/09/26"

#include <linux/config.h>
#include <linux/module.h>

#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/malloc.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/stat.h>
#include <linux/blk.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/init.h>

#define __KERNEL_SYSCALLS__

#include <linux/unistd.h>
#include <linux/spinlock.h>

#include <asm/system.h>
#include <asm/irq.h>
#include <asm/dma.h>
#include <asm/uaccess.h>

#include "scsi.h"
#include "hosts.h"
#include "constants.h"

#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif

#undef USE_STATIC_SCSI_MEMORY

struct proc_dir_entry *proc_scsi;

#ifdef CONFIG_PROC_FS
static int scsi_proc_info(char *buffer, char **start, off_t offset, int length);
static void scsi_dump_status(int level);
#endif

/*
   static const char RCSid[] = "$Header: /vger/u4/cvs/linux/drivers/scsi/scsi.c,v 1.38 1997/01/19 23:07:18 davem Exp $";
 */

/*
 * Definitions and constants.
 */

#define MIN_RESET_DELAY (2*HZ)

/* Do not call reset on error if we just did a reset within 15 sec. */
#define MIN_RESET_PERIOD (15*HZ)


/*
 * Data declarations.
 */
unsigned long scsi_pid;
Scsi_Cmnd *last_cmnd;
/* Command groups 3 and 4 are reserved and should never be used.  */
const unsigned char scsi_command_size[8] =
{
	6, 10, 10, 12,
	12, 12, 10, 10
};
static unsigned long serial_number;
static Scsi_Cmnd *scsi_bh_queue_head;
static Scsi_Cmnd *scsi_bh_queue_tail;

/*
 * Note - the initial logging level can be set here to log events at boot time.
 * After the system is up, you may enable logging via the /proc interface.
 */
unsigned int scsi_logging_level;

const char *const scsi_device_types[MAX_SCSI_DEVICE_CODE] =
{
	"Direct-Access    ",
	"Sequential-Access",
	"Printer          ",
	"Processor        ",
	"WORM             ",
	"CD-ROM           ",
	"Scanner          ",
	"Optical Device   ",
	"Medium Changer   ",
	"Communications   ",
	"Unknown          ",
	"Unknown          ",
	"Unknown          ",
	"Enclosure        ",
};

/* 
 * Function prototypes.
 */
extern void scsi_times_out(Scsi_Cmnd * SCpnt);
void scsi_build_commandblocks(Scsi_Device * SDpnt);

/*
 * These are the interface to the old error handling code.  It should go away
 * someday soon.
 */
extern void scsi_old_done(Scsi_Cmnd * SCpnt);
extern void scsi_old_times_out(Scsi_Cmnd * SCpnt);


/*
 * Function:    scsi_initialize_queue()
 *
 * Purpose:     Selects queue handler function for a device.
 *
 * Arguments:   SDpnt   - device for which we need a handler function.
 *
 * Returns:     Nothing
 *
 * Lock status: No locking assumed or required.
 *
 * Notes:       Most devices will end up using scsi_request_fn for the
 *              handler function (at least as things are done now).
 *              The "block" feature basically ensures that only one of
 *              the blocked hosts is active at one time, mainly to work around
 *              buggy DMA chipsets where the memory gets starved.
 *              For this case, we have a special handler function, which
 *              does some checks and ultimately calls scsi_request_fn.
 *
 *              The single_lun feature is a similar special case.
 *
 *              We handle these things by stacking the handlers.  The
 *              special case handlers simply check a few conditions,
 *              and return if they are not supposed to do anything.
 *              In the event that things are OK, then they call the next
 *              handler in the list - ultimately they call scsi_request_fn
 *              to do the dirty deed.
 */
void  scsi_initialize_queue(Scsi_Device * SDpnt, struct Scsi_Host * SHpnt) {
	blk_init_queue(&SDpnt->request_queue, scsi_request_fn);
        blk_queue_headactive(&SDpnt->request_queue, 0);
        SDpnt->request_queue.queuedata = (void *) SDpnt;
}

#ifdef MODULE
MODULE_PARM(scsi_logging_level, "i");
MODULE_PARM_DESC(scsi_logging_level, "SCSI logging level; should be zero or nonzero");

#else

static int __init scsi_logging_setup(char *str)
{
	int tmp;

	if (get_option(&str, &tmp) == 1) {
		scsi_logging_level = (tmp ? ~0 : 0);
		return 1;
	} else {
		printk(KERN_INFO "scsi_logging_setup : usage scsi_logging_level=n "
		       "(n should be 0 or non-zero)\n");
		return 0;
	}
}

__setup("scsi_logging=", scsi_logging_setup);

#endif

/*
 *	Issue a command and wait for it to complete
 */
 
static void scsi_wait_done(Scsi_Cmnd * SCpnt)
{
	struct request *req;

	req = &SCpnt->request;
	req->rq_status = RQ_SCSI_DONE;	/* Busy, but indicate request done */

	if (req->sem != NULL) {
		up(req->sem);
	}
}

/*
 * This lock protects the freelist for all devices on the system.
 * We could make this finer grained by having a single lock per
 * device if it is ever found that there is excessive contention
 * on this lock.
 */
static spinlock_t device_request_lock = SPIN_LOCK_UNLOCKED;

/*
 * Used to protect insertion into and removal from the queue of
 * commands to be processed by the bottom half handler.
 */
static spinlock_t scsi_bhqueue_lock = SPIN_LOCK_UNLOCKED;

/*
 * Function:    scsi_allocate_request
 *
 * Purpose:     Allocate a request descriptor.
 *
 * Arguments:   device    - device for which we want a request
 *
 * Lock status: No locks assumed to be held.  This function is SMP-safe.
 *
 * Returns:     Pointer to request block.
 *
 * Notes:       With the new queueing code, it becomes important
 *              to track the difference between a command and a
 *              request.  A request is a pending item in the queue that
 *              has not yet reached the top of the queue.
 */

Scsi_Request *scsi_allocate_request(Scsi_Device * device)
{
  	Scsi_Request *SRpnt = NULL;
  
  	if (!device)
  		panic("No device passed to scsi_allocate_request().\n");
  
	SRpnt = (Scsi_Request *) kmalloc(sizeof(Scsi_Request), GFP_ATOMIC);
	if( SRpnt == NULL )
	{
		return NULL;
	}

	memset(SRpnt, 0, sizeof(Scsi_Request));
	SRpnt->sr_device = device;
	SRpnt->sr_host = device->host;
	SRpnt->sr_magic = SCSI_REQ_MAGIC;
	SRpnt->sr_data_direction = SCSI_DATA_UNKNOWN;

	return SRpnt;
}

/*
 * Function:    scsi_release_request
 *
 * Purpose:     Release a request descriptor.
 *
 * Arguments:   device    - device for which we want a request
 *
 * Lock status: No locks assumed to be held.  This function is SMP-safe.
 *
 * Returns:     Pointer to request block.
 *
 * Notes:       With the new queueing code, it becomes important
 *              to track the difference between a command and a
 *              request.  A request is a pending item in the queue that
 *              has not yet reached the top of the queue.  We still need
 *              to free a request when we are done with it, of course.
 */
void scsi_release_request(Scsi_Request * req)
{
	if( req->sr_command != NULL )
	{
		scsi_release_command(req->sr_command);
		req->sr_command = NULL;
	}

	kfree(req);
}

/*
 * Function:    scsi_allocate_device
 *
 * Purpose:     Allocate a command descriptor.
 *
 * Arguments:   device    - device for which we want a command descriptor
 *              wait      - 1 if we should wait in the event that none
 *                          are available.
 *              interruptible - 1 if we should unblock and return NULL
 *                          in the event that we must wait, and a signal
 *                          arrives.
 *
 * Lock status: No locks assumed to be held.  This function is SMP-safe.
 *
 * Returns:     Pointer to command descriptor.
 *
 * Notes:       Prior to the new queue code, this function was not SMP-safe.
 *
 *              If the wait flag is true, and we are waiting for a free
 *              command block, this function will interrupt and return
 *              NULL in the event that a signal arrives that needs to
 *              be handled.
 *
 *              This function is deprecated, and drivers should be
 *              rewritten to use Scsi_Request instead of Scsi_Cmnd.
 */

Scsi_Cmnd *scsi_allocate_device(Scsi_Device * device, int wait, 
                                int interruptable)
{
 	struct Scsi_Host *host;
  	Scsi_Cmnd *SCpnt = NULL;
	Scsi_Device *SDpnt;
	unsigned long flags;
  
  	if (!device)
  		panic("No device passed to scsi_allocate_device().\n");
  
  	host = device->host;
  
	spin_lock_irqsave(&device_request_lock, flags);
 
	while (1 == 1) {
		SCpnt = NULL;
		if (!device->device_blocked) {
			if (device->single_lun) {
				/*
				 * FIXME(eric) - this is not at all optimal.  Given that
				 * single lun devices are rare and usually slow
				 * (i.e. CD changers), this is good enough for now, but
				 * we may want to come back and optimize this later.
				 *
				 * Scan through all of the devices attached to this
				 * host, and see if any are active or not.  If so,
				 * we need to defer this command.
				 *
				 * We really need a busy counter per device.  This would
				 * allow us to more easily figure out whether we should
				 * do anything here or not.
				 */
				for (SDpnt = host->host_queue;
				     SDpnt;
				     SDpnt = SDpnt->next) {
					/*
					 * Only look for other devices on the same bus
					 * with the same target ID.
					 */
					if (SDpnt->channel != device->channel
					    || SDpnt->id != device->id
					    || SDpnt == device) {
 						continue;
					}
                                        if( atomic_read(&SDpnt->device_active) != 0)
                                        {
                                                break;
                                        }
				}
				if (SDpnt) {
					/*
					 * Some other device in this cluster is busy.
					 * If asked to wait, we need to wait, otherwise
					 * return NULL.
					 */
					SCpnt = NULL;
					goto busy;
				}
			}
			/*
			 * Now we can check for a free command block for this device.
			 */
			for (SCpnt = device->device_queue; SCpnt; SCpnt = SCpnt->next) {
				if (SCpnt->request.rq_status == RQ_INACTIVE)
					break;
			}
		}
		/*
		 * If we couldn't find a free command block, and we have been
		 * asked to wait, then do so.
		 */
		if (SCpnt) {
			break;
		}
      busy:
		/*
		 * If we have been asked to wait for a free block, then
		 * wait here.
		 */
		if (wait) {
                        DECLARE_WAITQUEUE(wait, current);

                        /*
                         * We need to wait for a free commandblock.  We need to
                         * insert ourselves into the list before we release the
                         * lock.  This way if a block were released the same
                         * microsecond that we released the lock, the call
                         * to schedule() wouldn't block (well, it might switch,
                         * but the current task will still be schedulable.
                         */
                        add_wait_queue(&device->scpnt_wait, &wait);
                        if( interruptable ) {
                                set_current_state(TASK_INTERRUPTIBLE);
                        } else {
                                set_current_state(TASK_UNINTERRUPTIBLE);
                        }

                        spin_unlock_irqrestore(&device_request_lock, flags);

			/*
			 * This should block until a device command block