share.c

Linux内核源代码 为压缩文件 是<<Linux内核>>一书中的源代码

/* $Id: parport_share.c,v 1.15 1998/01/11 12:06:17 philip Exp $
 * Parallel-port resource manager code.
 * 
 * Authors: David Campbell <[e-mail]>
 *          Tim Waugh <[e-mail]>
 *          Jose Renau <[e-mail]>
 *          Philip Blundell <[e-mail]>
 *	    Andrea Arcangeli
 *
 * based on work by Grant Guenther <[e-mail]>
 *          and Philip Blundell
 *
 * Any part of this program may be used in documents licensed under
 * the GNU Free Documentation License, Version 1.1 or any later version
 * published by the Free Software Foundation.
 */

#undef PARPORT_DEBUG_SHARING		/* undef for production */

#include <linux/config.h>
#include <linux/string.h>
#include <linux/threads.h>
#include <linux/parport.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/malloc.h>
#include <linux/sched.h>
#include <linux/kmod.h>

#include <linux/spinlock.h>
#include <asm/irq.h>

#undef PARPORT_PARANOID

#define PARPORT_DEFAULT_TIMESLICE	(HZ/5)

unsigned long parport_default_timeslice = PARPORT_DEFAULT_TIMESLICE;
int parport_default_spintime =  DEFAULT_SPIN_TIME;

static struct parport *portlist = NULL, *portlist_tail = NULL;
spinlock_t parportlist_lock = SPIN_LOCK_UNLOCKED;

static struct parport_driver *driver_chain = NULL;
spinlock_t driverlist_lock = SPIN_LOCK_UNLOCKED;

/* What you can do to a port that's gone away.. */
static void dead_write_lines (struct parport *p, unsigned char b){}
static unsigned char dead_read_lines (struct parport *p) { return 0; }
static unsigned char dead_frob_lines (struct parport *p, unsigned char b,
			     unsigned char c) { return 0; }
static void dead_onearg (struct parport *p){}
static void dead_initstate (struct pardevice *d, struct parport_state *s) { }
static void dead_state (struct parport *p, struct parport_state *s) { }
static void dead_noargs (void) { }
static size_t dead_write (struct parport *p, const void *b, size_t l, int f)
{ return 0; }
static size_t dead_read (struct parport *p, void *b, size_t l, int f)
{ return 0; }
static struct parport_operations dead_ops = {
	dead_write_lines,	/* data */
	dead_read_lines,
	dead_write_lines,	/* control */
	dead_read_lines,
	dead_frob_lines,
	dead_read_lines,	/* status */
	dead_onearg,		/* enable_irq */
	dead_onearg,		/* disable_irq */
	dead_onearg,		/* data_forward */
	dead_onearg,		/* data_reverse */
	dead_initstate,		/* init_state */
	dead_state,
	dead_state,
	dead_noargs,		/* xxx_use_count */
	dead_noargs,
	dead_write,		/* epp */
	dead_read,
	dead_write,
	dead_read,
	dead_write,		/* ecp */
	dead_read,
	dead_write,
	dead_write,		/* compat */
	dead_read,		/* nibble */
	dead_read		/* byte */
};

/* Call attach(port) for each registered driver. */
static void attach_driver_chain(struct parport *port)
{
	struct parport_driver *drv;
	void (**attach) (struct parport *);
	int count = 0, i;

	/* This is complicated because attach() must be able to block,
	 * but we can't let it do that while we're holding a
	 * spinlock. */

	spin_lock (&driverlist_lock);
	for (drv = driver_chain; drv; drv = drv->next)
		count++;
	spin_unlock (&driverlist_lock);

	/* Drivers can unregister here; that's okay.  If they register
	 * they'll be given an attach during parport_register_driver,
	 * so that's okay too.  The only worry is that someone might
	 * get given an attach twice if they registered just before
	 * this function gets called. */

	/* Hmm, this could be fixed with a generation number..
	 * FIXME */

	attach = kmalloc (sizeof (void(*)(struct parport *)) * count,
			  GFP_KERNEL);
	if (!attach) {
		printk (KERN_WARNING "parport: not enough memory to attach\n");
		return;
	}

	spin_lock (&driverlist_lock);
	for (i = 0, drv = driver_chain; drv && i < count; drv = drv->next)
		attach[i++] = drv->attach;
	spin_unlock (&driverlist_lock);

	for (count = 0; count < i; count++)
		(*attach[count]) (port);

	kfree (attach);
}

/* Call detach(port) for each registered driver. */
static void detach_driver_chain(struct parport *port)
{
	struct parport_driver *drv;

	spin_lock (&driverlist_lock);
	for (drv = driver_chain; drv; drv = drv->next)
		drv->detach (port);
	spin_unlock (&driverlist_lock);
}

/* Ask kmod for some lowlevel drivers. */
static void get_lowlevel_driver (void)
{
	/* There is no actual module called this: you should set
	 * up an alias for modutils. */
	request_module ("parport_lowlevel");
}

/**
 *	parport_register_driver - register a parallel port device driver
 *	@drv: structure describing the driver
 *
 *	This can be called by a parallel port device driver in order
 *	to receive notifications about ports being found in the
 *	system, as well as ports no longer available.
 *
 *	The @drv structure is allocated by the caller and must not be
 *	deallocated until after calling parport_unregister_driver().
 *
 *	The driver's attach() function may block.  The port that
 *	attach() is given will be valid for the duration of the
 *	callback, but if the driver wants to take a copy of the
 *	pointer it must call parport_get_port() to do so.  Calling
 *	parport_register_device() on that port will do this for you.
 *
 *	The driver's detach() function may not block.  The port that
 *	detach() is given will be valid for the duration of the
 *	callback, but if the driver wants to take a copy of the
 *	pointer it must call parport_get_port() to do so.
 *
 *	Returns 0 on success.  Currently it always succeeds.
 **/

int parport_register_driver (struct parport_driver *drv)
{
	struct parport *port;
	struct parport **ports;
	int count = 0, i;

	if (!portlist)
		get_lowlevel_driver ();

	/* We have to take the portlist lock for this to be sure
	 * that port is valid for the duration of the callback. */

	/* This is complicated by the fact that attach must be allowed
	 * to block, so we can't be holding any spinlocks when we call
	 * it.  But we need to hold a spinlock to iterate over the
	 * list of ports.. */

	spin_lock (&parportlist_lock);
	for (port = portlist; port; port = port->next)
		count++;
	spin_unlock (&parportlist_lock);

	ports = kmalloc (sizeof (struct parport *) * count, GFP_KERNEL);
	if (!ports)
		printk (KERN_WARNING "parport: not enough memory to attach\n");
	else {
		spin_lock (&parportlist_lock);
		for (i = 0, port = portlist; port && i < count;
		     port = port->next)
			ports[i++] = port;
		spin_unlock (&parportlist_lock);

		for (count = 0; count < i; count++)
			drv->attach (ports[count]);

		kfree (ports);
	}

	spin_lock (&driverlist_lock);
	drv->next = driver_chain;
	driver_chain = drv;
	spin_unlock (&driverlist_lock);

	return 0;
}

/**
 *	parport_unregister_driver - deregister a parallel port device driver
 *	@arg: structure describing the driver that was given to
 *	      parport_register_driver()
 *
 *	This should be called by a parallel port device driver that
 *	has registered itself using parport_register_driver() when it
 *	is about to be unloaded.
 *
 *	When it returns, the driver's attach() routine will no longer
 *	be called, and for each port that attach() was called for, the
 *	detach() routine will have been called.
 *
 *	If the caller's attach() function can block, it is their
 *	responsibility to make sure to wait for it to exit before
 *	unloading.
 *
 *	All the driver's detach() calls are guaranteed to have
 *	finished by the time this function returns.
 *
 *	The driver's detach() call is not allowed to block.
 **/

void parport_unregister_driver (struct parport_driver *arg)
{
	struct parport_driver *drv = driver_chain, *olddrv = NULL;

	while (drv) {
		if (drv == arg) {
			struct parport *port;

			spin_lock (&driverlist_lock);
			if (olddrv)
				olddrv->next = drv->next;
			else
				driver_chain = drv->next;
			spin_unlock (&driverlist_lock);

			/* Call the driver's detach routine for each
			 * port to clean up any resources that the
			 * attach routine acquired. */
			spin_lock (&parportlist_lock);
			for (port = portlist; port; port = port->next)
				drv->detach (port);
			spin_unlock (&parportlist_lock);

			return;
		}
		olddrv = drv;
		drv = drv->next;
	}
}

static void free_port (struct parport *port)
{
	int d;
	for (d = 0; d < 5; d++) {
		if (port->probe_info[d].class_name)
			kfree (port->probe_info[d].class_name);
		if (port->probe_info[d].mfr)
			kfree (port->probe_info[d].mfr);
		if (port->probe_info[d].model)
			kfree (port->probe_info[d].model);
		if (port->probe_info[d].cmdset)
			kfree (port->probe_info[d].cmdset);
		if (port->probe_info[d].description)
			kfree (port->probe_info[d].description);
	}

	kfree(port->name);
	kfree(port);
}

/**
 *	parport_get_port - increment a port's reference count
 *	@port: the port
 *
 *	This ensure's that a struct parport pointer remains valid
 *	until the matching parport_put_port() call.
 **/

struct parport *parport_get_port (struct parport *port)
{
	atomic_inc (&port->ref_count);
	return port;
}

/**
 *	parport_put_port - decrement a port's reference count
 *	@port: the port
 *
 *	This should be called once for each call to parport_get_port(),
 *	once the port is no longer needed.
 **/

void parport_put_port (struct parport *port)
{
	if (atomic_dec_and_test (&port->ref_count))
		/* Can destroy it now. */
		free_port (port);

	return;
}

/**
 *	parport_enumerate - return a list of the system's parallel ports
 *
 *	This returns the head of the list of parallel ports in the
 *	system, as a &struct parport.  The structure that is returned
 *	describes the first port in the list, and its 'next' member
 *	points to the next port, or %NULL if it's the last port.
 *
 *	If there are no parallel ports in the system,
 *	parport_enumerate() will return %NULL.
 **/

struct parport *parport_enumerate(void)
{
	/* Don't use this: use parport_register_driver instead. */

	if (!portlist)
		get_lowlevel_driver ();

	return portlist;
}

/**
 *	parport_register_port - register a parallel port
 *	@base: base I/O address
 *	@irq: IRQ line
 *	@dma: DMA channel
 *	@ops: pointer to the port driver's port operations structure
 *
 *	When a parallel port (lowlevel) driver finds a port that
 *	should be made available to parallel port device drivers, it
 *	should call parport_register_port().  The @base, @irq, and
 *	@dma parameters are for the convenience of port drivers, and
 *	for ports where they aren't meaningful needn't be set to
 *	anything special.  They can be altered afterwards by adjusting
 *	the relevant members of the parport structure that is returned
 *	and represents the port.  They should not be tampered with
 *	after calling parport_announce_port, however.
 *
 *	If there are parallel port device drivers in the system that
 *	have registered themselves using parport_register_driver(),
 *	they are not told about the port at this time; that is done by
 *	parport_announce_port().
 *
 *	The @ops structure is allocated by the caller, and must not be
 *	deallocated before calling parport_unregister_port().
 *