pseudo.h

底层驱动开发

/* 
        pseudo.h    (c) 1997-8  Grant R. Guenther <[e-mail]>
                                Under the terms of the GNU General Public License.

	This is the "pseudo-interrupt" logic for parallel port drivers.

        This module is #included into each driver.  It makes one
        function available:

		ps_set_intr( void (*continuation)(void),
			     int  (*ready)(void),
			     int timeout,
			     int nice )

	Which will arrange for ready() to be evaluated frequently and
	when either it returns true, or timeout jiffies have passed,
	continuation() will be invoked.

	If nice is 1, the test will done approximately once a
	jiffy.  If nice is 0, the test will also be done whenever
	the scheduler runs (by adding it to a task queue).  If
	nice is greater than 1, the test will be done once every
	(nice-1) jiffies. 

*/

/* Changes:

	1.01	1998.05.03	Switched from cli()/sti() to spinlocks
	1.02    1998.12.14      Added support for nice > 1
*/
	
#define PS_VERSION	"1.02"

#include <linux/sched.h>
#include <linux/workqueue.h>

static void ps_tq_int( void *data);

static void (* ps_continuation)(void);
static int (* ps_ready)(void);
static unsigned long ps_timeout;
static int ps_tq_active = 0;
static int ps_nice = 0;

static DEFINE_SPINLOCK(ps_spinlock __attribute__((unused)));

static DECLARE_WORK(ps_tq, ps_tq_int, NULL);

static void ps_set_intr(void (*continuation)(void), 
			int (*ready)(void),
			int timeout, int nice)
{
	unsigned long	flags;

	spin_lock_irqsave(&ps_spinlock,flags);

	ps_continuation = continuation;
	ps_ready = ready;
	ps_timeout = jiffies + timeout;
	ps_nice = nice;

	if (!ps_tq_active) {
		ps_tq_active = 1;
		if (!ps_nice)
			schedule_work(&ps_tq);
		else
			schedule_delayed_work(&ps_tq, ps_nice-1);
	}
	spin_unlock_irqrestore(&ps_spinlock,flags);
}

static void ps_tq_int(void *data)
{
	void (*con)(void);
	unsigned long flags;

	spin_lock_irqsave(&ps_spinlock,flags);

	con = ps_continuation;
	ps_tq_active = 0;

	if (!con) {
		spin_unlock_irqrestore(&ps_spinlock,flags);
		return;
	}
	if (!ps_ready || ps_ready() || time_after_eq(jiffies, ps_timeout)) {
		ps_continuation = NULL;
		spin_unlock_irqrestore(&ps_spinlock,flags);
		con();
		return;
	}
	ps_tq_active = 1;
	if (!ps_nice)
		schedule_work(&ps_tq);
	else
		schedule_delayed_work(&ps_tq, ps_nice-1);
	spin_unlock_irqrestore(&ps_spinlock,flags);
}

/* end of pseudo.h */