kernel26-2.6.12-alx-r9/kernel/dma.c

/* $Id: dma.c,v 1.7 1994/12/28 03:35:33 root Exp root $
 * linux/kernel/dma.c: A DMA channel allocator. Inspired by linux/kernel/irq.c.
 *
 * Written by Hennus Bergman, 1992.
 *
 * 1994/12/26: Changes by Alex Nash to fix a minor bug in /proc/dma.
 *   In the previous version the reported device could end up being wrong,
 *   if a device requested a DMA channel that was already in use.
 *   [It also happened to remove the sizeof(char *) == sizeof(int)
 *   assumption introduced because of those /proc/dma patches. -- Hennus]
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <asm/dma.h>
#include <asm/system.h>

 
/* A note on resource allocation:
 *
 * All drivers needing DMA channels, should allocate and release them
 * through the public routines `request_dma()' and `free_dma()'.
 *
 * In order to avoid problems, all processes should allocate resources in
 * the same sequence and release them in the reverse order.
 *
 * So, when allocating DMAs and IRQs, first allocate the IRQ, then the DMA.
 * When releasing them, first release the DMA, then release the IRQ.
 * If you don't, you may cause allocation requests to fail unnecessarily.
 * This doesn't really matter now, but it will once we get real semaphores
 * in the kernel.
 */


DEFINE_SPINLOCK(dma_spin_lock);

/*
 *	If our port doesn't define this it has no PC like DMA
 */

#ifdef MAX_DMA_CHANNELS


/* Channel n is busy iff dma_chan_busy[n].lock != 0.
 * DMA0 used to be reserved for DRAM refresh, but apparently not any more...
 * DMA4 is reserved for cascading.
 */

struct dma_chan {
	int  lock;
	const char *device_id;
};

static struct dma_chan dma_chan_busy[MAX_DMA_CHANNELS] = {
	[4] = { 1, "cascade" },
};


int request_dma(unsigned int dmanr, const char * device_id)
{
	if (dmanr >= MAX_DMA_CHANNELS)
		return -EINVAL;

	if (xchg(&dma_chan_busy[dmanr].lock, 1) != 0)
		return -EBUSY;

	dma_chan_busy[dmanr].device_id = device_id;

	/* old flag was 0, now contains 1 to indicate busy */
	return 0;
} /* request_dma */


void free_dma(unsigned int dmanr)
{
	if (dmanr >= MAX_DMA_CHANNELS) {
		printk(KERN_WARNING "Trying to free DMA%d\n", dmanr);
		return;
	}

	if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) {
		printk(KERN_WARNING "Trying to free free DMA%d\n", dmanr);
		return;
	}	

} /* free_dma */

#else

int request_dma(unsigned int dmanr, const char *device_id)
{
	return -EINVAL;
}

void free_dma(unsigned int dmanr)
{
}

#endif

#ifdef CONFIG_PROC_FS

#ifdef MAX_DMA_CHANNELS
static int proc_dma_show(struct seq_file *m, void *v)
{
	int i;

	for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) {
		if (dma_chan_busy[i].lock) {
		    seq_printf(m, "%2d: %s\n", i,
			       dma_chan_busy[i].device_id);
		}
	}
	return 0;
}
#else
static int proc_dma_show(struct seq_file *m, void *v)
{
	seq_puts(m, "No DMA\n");
	return 0;
}
#endif /* MAX_DMA_CHANNELS */

static int proc_dma_open(struct inode *inode, struct file *file)
{
	return single_open(file, proc_dma_show, NULL);
}

static struct file_operations proc_dma_operations = {
	.open		= proc_dma_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int __init proc_dma_init(void)
{
	struct proc_dir_entry *e;

	e = create_proc_entry("dma", 0, NULL);
	if (e)
		e->proc_fops = &proc_dma_operations;

	return 0;
}

__initcall(proc_dma_init);
#endif

EXPORT_SYMBOL(request_dma);
EXPORT_SYMBOL(free_dma);
EXPORT_SYMBOL(dma_spin_lock);
1	/* $Id: dma.c,v 1.7 1994/12/28 03:35:33 root Exp root $
2	* linux/kernel/dma.c: A DMA channel allocator. Inspired by linux/kernel/irq.c.
3	*
4	* Written by Hennus Bergman, 1992.
5	*
6	* 1994/12/26: Changes by Alex Nash to fix a minor bug in /proc/dma.
7	* In the previous version the reported device could end up being wrong,
8	* if a device requested a DMA channel that was already in use.
9	* [It also happened to remove the sizeof(char *) == sizeof(int)
10	* assumption introduced because of those /proc/dma patches. -- Hennus]
11	*/
12	#include <linux/module.h>
13	#include <linux/kernel.h>
14	#include <linux/errno.h>
15	#include <linux/spinlock.h>
16	#include <linux/string.h>
17	#include <linux/seq_file.h>
18	#include <linux/proc_fs.h>
19	#include <linux/init.h>
20	#include <asm/dma.h>
21	#include <asm/system.h>
22
23
24
25	/* A note on resource allocation:
26	*
27	* All drivers needing DMA channels, should allocate and release them
28	* through the public routines `request_dma()' and `free_dma()'.
29	*
30	* In order to avoid problems, all processes should allocate resources in
31	* the same sequence and release them in the reverse order.
32	*
33	* So, when allocating DMAs and IRQs, first allocate the IRQ, then the DMA.
34	* When releasing them, first release the DMA, then release the IRQ.
35	* If you don't, you may cause allocation requests to fail unnecessarily.
36	* This doesn't really matter now, but it will once we get real semaphores
37	* in the kernel.
38	*/
39
40
41	DEFINE_SPINLOCK(dma_spin_lock);
42
43	/*
44	* If our port doesn't define this it has no PC like DMA
45	*/
46
47	#ifdef MAX_DMA_CHANNELS
48
49
50	/* Channel n is busy iff dma_chan_busy[n].lock != 0.
51	* DMA0 used to be reserved for DRAM refresh, but apparently not any more...
52	* DMA4 is reserved for cascading.
53	*/
54
55	struct dma_chan {
56	int lock;
57	const char *device_id;
58	};
59
60	static struct dma_chan dma_chan_busy[MAX_DMA_CHANNELS] = {
61	[4] = { 1, "cascade" },
62	};
63
64
65	int request_dma(unsigned int dmanr, const char * device_id)
66	{
67	if (dmanr >= MAX_DMA_CHANNELS)
68	return -EINVAL;
69
70	if (xchg(&dma_chan_busy[dmanr].lock, 1) != 0)
71	return -EBUSY;
72
73	dma_chan_busy[dmanr].device_id = device_id;
74
75	/* old flag was 0, now contains 1 to indicate busy */
76	return 0;
77	} /* request_dma */
78
79
80	void free_dma(unsigned int dmanr)
81	{
82	if (dmanr >= MAX_DMA_CHANNELS) {
83	printk(KERN_WARNING "Trying to free DMA%d\n", dmanr);
84	return;
85	}
86
87	if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) {
88	printk(KERN_WARNING "Trying to free free DMA%d\n", dmanr);
89	return;
90	}
91
92	} /* free_dma */
93
94	#else
95
96	int request_dma(unsigned int dmanr, const char *device_id)
97	{
98	return -EINVAL;
99	}
100
101	void free_dma(unsigned int dmanr)
102	{
103	}
104
105	#endif
106
107	#ifdef CONFIG_PROC_FS
108
109	#ifdef MAX_DMA_CHANNELS
110	static int proc_dma_show(struct seq_file m, void v)
111	{
112	int i;
113
114	for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) {
115	if (dma_chan_busy[i].lock) {
116	seq_printf(m, "%2d: %s\n", i,
117	dma_chan_busy[i].device_id);
118	}
119	}
120	return 0;
121	}
122	#else
123	static int proc_dma_show(struct seq_file m, void v)
124	{
125	seq_puts(m, "No DMA\n");
126	return 0;
127	}
128	#endif /* MAX_DMA_CHANNELS */
129
130	static int proc_dma_open(struct inode inode, struct file file)
131	{
132	return single_open(file, proc_dma_show, NULL);
133	}
134
135	static struct file_operations proc_dma_operations = {
136	.open = proc_dma_open,
137	.read = seq_read,
138	.llseek = seq_lseek,
139	.release = single_release,
140	};
141
142	static int __init proc_dma_init(void)
143	{
144	struct proc_dir_entry *e;
145
146	e = create_proc_entry("dma", 0, NULL);
147	if (e)
148	e->proc_fops = &proc_dma_operations;
149
150	return 0;
151	}
152
153	__initcall(proc_dma_init);
154	#endif
155
156	EXPORT_SYMBOL(request_dma);
157	EXPORT_SYMBOL(free_dma);
158	EXPORT_SYMBOL(dma_spin_lock);