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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [kernel/] [dma.c] - Blame information for rev 1779

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/* $Id: dma.c,v 1.1.1.1 2004-04-15 02:30:21 phoenix Exp $
 * 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/kernel.h>
#include <linux/errno.h>
#include <linux/spinlock.h>
#include <linux/string.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.
 */
 
 
spinlock_t dma_spin_lock = SPIN_LOCK_UNLOCKED;
 
/*
 *      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] = {
        { 0, 0 },
        { 0, 0 },
        { 0, 0 },
        { 0, 0 },
        { 1, "cascade" },
        { 0, 0 },
        { 0, 0 },
        { 0, 0 }
};
 
int get_dma_list(char *buf)
{
        int i, len = 0;
 
        for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) {
                if (dma_chan_busy[i].lock) {
                    len += sprintf(buf+len, "%2d: %s\n",
                                   i,
                                   dma_chan_busy[i].device_id);
                }
        }
        return len;
} /* get_dma_list */
 
 
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("Trying to free DMA%d\n", dmanr);
                return;
        }
 
        if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) {
                printk("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)
{
}
 
int get_dma_list(char *buf)
{
        strcpy(buf, "No DMA\n");
        return 7;
}
#endif

Line No.	Rev	Author	Line
1	1275	phoenix	`/* $Id: dma.c,v 1.1.1.1 2004-04-15 02:30:21 phoenix Exp $`
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
13			`#include <linux/kernel.h>`
14			`#include <linux/errno.h>`
15			`#include <linux/spinlock.h>`
16			`#include <linux/string.h>`
17			`#include <asm/dma.h>`
18			`#include <asm/system.h>`
19
20
21
22			`/* A note on resource allocation:`
23			`*`
24			`* All drivers needing DMA channels, should allocate and release them`
25			* through the public routines `request_dma()' and `free_dma()'.
26			`*`
27			`* In order to avoid problems, all processes should allocate resources in`
28			`* the same sequence and release them in the reverse order.`
29			`*`
30			`* So, when allocating DMAs and IRQs, first allocate the IRQ, then the DMA.`
31			`* When releasing them, first release the DMA, then release the IRQ.`
32			`* If you don't, you may cause allocation requests to fail unnecessarily.`
33			`* This doesn't really matter now, but it will once we get real semaphores`
34			`* in the kernel.`
35			`*/`
36
37
38			`spinlock_t dma_spin_lock = SPIN_LOCK_UNLOCKED;`
39
40			`/*`
41			`* If our port doesn't define this it has no PC like DMA`
42			`*/`
43
44			`#ifdef MAX_DMA_CHANNELS`
45
46
47			`/* Channel n is busy iff dma_chan_busy[n].lock != 0.`
48			`* DMA0 used to be reserved for DRAM refresh, but apparently not any more...`
49			`* DMA4 is reserved for cascading.`
50			`*/`
51
52			`struct dma_chan {`
53			`int lock;`
54			`const char *device_id;`
55			`};`
56
57			`static struct dma_chan dma_chan_busy[MAX_DMA_CHANNELS] = {`
58			`{ 0, 0 },`
59			`{ 0, 0 },`
60			`{ 0, 0 },`
61			`{ 0, 0 },`
62			`{ 1, "cascade" },`
63			`{ 0, 0 },`
64			`{ 0, 0 },`
65			`{ 0, 0 }`
66			`};`
67
68			`int get_dma_list(char *buf)`
69			`{`
70			`int i, len = 0;`
71
72			`for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) {`
73			`if (dma_chan_busy[i].lock) {`
74			`len += sprintf(buf+len, "%2d: %s\n",`
75			`i,`
76			`dma_chan_busy[i].device_id);`
77			`}`
78			`}`
79			`return len;`
80			`} /* get_dma_list */`
81
82
83			`int request_dma(unsigned int dmanr, const char * device_id)`
84			`{`
85			`if (dmanr >= MAX_DMA_CHANNELS)`
86			`return -EINVAL;`
87
88			`if (xchg(&dma_chan_busy[dmanr].lock, 1) != 0)`
89			`return -EBUSY;`
90
91			`dma_chan_busy[dmanr].device_id = device_id;`
92
93			`/* old flag was 0, now contains 1 to indicate busy */`
94			`return 0;`
95			`} /* request_dma */`
96
97
98			`void free_dma(unsigned int dmanr)`
99			`{`
100			`if (dmanr >= MAX_DMA_CHANNELS) {`
101			`printk("Trying to free DMA%d\n", dmanr);`
102			`return;`
103			`}`
104
105			`if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) {`
106			`printk("Trying to free free DMA%d\n", dmanr);`
107			`return;`
108			`}`
109
110			`} /* free_dma */`
111
112			`#else`
113
114			`int request_dma(unsigned int dmanr, const char *device_id)`
115			`{`
116			`return -EINVAL;`
117			`}`
118
119			`void free_dma(unsigned int dmanr)`
120			`{`
121			`}`
122
123			`int get_dma_list(char *buf)`
124			`{`
125			`strcpy(buf, "No DMA\n");`
126			`return 7;`
127			`}`
128			`#endif`

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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [kernel/] [dma.c] - Blame information for rev 1779