mirror of
https://github.com/torvalds/linux.git
synced 2024-11-08 21:21:47 +00:00
9ffc93f203
Remove all #inclusions of asm/system.h preparatory to splitting and killing it. Performed with the following command: perl -p -i -e 's!^#\s*include\s*<asm/system[.]h>.*\n!!' `grep -Irl '^#\s*include\s*<asm/system[.]h>' *` Signed-off-by: David Howells <dhowells@redhat.com>
161 lines
3.6 KiB
C
161 lines
3.6 KiB
C
/*
|
|
* 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/export.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>
|
|
|
|
|
|
|
|
/* 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" },
|
|
};
|
|
|
|
|
|
/**
|
|
* request_dma - request and reserve a system DMA channel
|
|
* @dmanr: DMA channel number
|
|
* @device_id: reserving device ID string, used in /proc/dma
|
|
*/
|
|
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 */
|
|
|
|
/**
|
|
* free_dma - free a reserved system DMA channel
|
|
* @dmanr: DMA channel number
|
|
*/
|
|
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 const 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)
|
|
{
|
|
proc_create("dma", 0, NULL, &proc_dma_operations);
|
|
return 0;
|
|
}
|
|
|
|
__initcall(proc_dma_init);
|
|
#endif
|
|
|
|
EXPORT_SYMBOL(request_dma);
|
|
EXPORT_SYMBOL(free_dma);
|
|
EXPORT_SYMBOL(dma_spin_lock);
|