i8237.c

底层驱动开发

/*
 * i8237.c: 8237A DMA controller suspend functions.
 *
 * Written by Pierre Ossman, 2005.
 */

#include <linux/init.h>
#include <linux/sysdev.h>

#include <asm/dma.h>

/*
 * This module just handles suspend/resume issues with the
 * 8237A DMA controller (used for ISA and LPC).
 * Allocation is handled in kernel/dma.c and normal usage is
 * in asm/dma.h.
 */

static int i8237A_resume(struct sys_device *dev)
{
	unsigned long flags;
	int i;

	flags = claim_dma_lock();

	dma_outb(DMA1_RESET_REG, 0);
	dma_outb(DMA2_RESET_REG, 0);

	for (i = 0;i < 8;i++) {
		set_dma_addr(i, 0x000000);
		/* DMA count is a bit weird so this is not 0 */
		set_dma_count(i, 1);
	}

	/* Enable cascade DMA or channel 0-3 won't work */
	enable_dma(4);

	release_dma_lock(flags);

	return 0;
}

static int i8237A_suspend(struct sys_device *dev, pm_message_t state)
{
	return 0;
}

static struct sysdev_class i8237_sysdev_class = {
	set_kset_name("i8237"),
	.suspend = i8237A_suspend,
	.resume = i8237A_resume,
};

static struct sys_device device_i8237A = {
	.id	= 0,
	.cls	= &i8237_sysdev_class,
};

static int __init i8237A_init_sysfs(void)
{
	int error = sysdev_class_register(&i8237_sysdev_class);
	if (!error)
		error = sysdev_register(&device_i8237A);
	return error;
}

device_initcall(i8237A_init_sysfs);