Release 4.15 kernel/dma.c
// SPDX-License-Identifier: GPL-2.0
/*
* 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;
} Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Linus Torvalds (pre-git) | 58 | 100.00% | 5 | 100.00% |
| Total | 58 | 100.00% | 5 | 100.00% |
/* 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;
}
} Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Linus Torvalds (pre-git) | 52 | 96.30% | 4 | 80.00% |
| Cory Watson | 2 | 3.70% | 1 | 20.00% |
| Total | 54 | 100.00% | 5 | 100.00% |
/* free_dma */
#else
int request_dma(unsigned int dmanr, const char *device_id)
{
return -EINVAL;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Sam Ravnborg | 18 | 100.00% | 1 | 100.00% |
| Total | 18 | 100.00% | 1 | 100.00% |
void free_dma(unsigned int dmanr)
{
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Sam Ravnborg | 8 | 100.00% | 1 | 100.00% |
| Total | 8 | 100.00% | 1 | 100.00% |
#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;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Russell King | 63 | 100.00% | 1 | 100.00% |
| Total | 63 | 100.00% | 1 | 100.00% |
#else
static int proc_dma_show(struct seq_file *m, void *v)
{
seq_puts(m, "No DMA\n");
return 0;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Russell King | 25 | 100.00% | 1 | 100.00% |
| Total | 25 | 100.00% | 1 | 100.00% |
#endif /* MAX_DMA_CHANNELS */
static int proc_dma_open(struct inode *inode, struct file *file)
{
return single_open(file, proc_dma_show, NULL);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Russell King | 24 | 92.31% | 1 | 50.00% |
| Linus Torvalds (pre-git) | 2 | 7.69% | 1 | 50.00% |
| Total | 26 | 100.00% | 2 | 100.00% |
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;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Russell King | 17 | 70.83% | 1 | 33.33% |
| Linus Torvalds (pre-git) | 4 | 16.67% | 1 | 33.33% |
| Denis V. Lunev | 3 | 12.50% | 1 | 33.33% |
| Total | 24 | 100.00% | 3 | 100.00% |
__initcall(proc_dma_init);
#endif
EXPORT_SYMBOL(request_dma);
EXPORT_SYMBOL(free_dma);
EXPORT_SYMBOL(dma_spin_lock);
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Russell King | 181 | 43.30% | 1 | 4.55% |
| Linus Torvalds (pre-git) | 172 | 41.15% | 10 | 45.45% |
| Sam Ravnborg | 37 | 8.85% | 1 | 4.55% |
| Art Haas | 8 | 1.91% | 1 | 4.55% |
| Linus Torvalds | 5 | 1.20% | 1 | 4.55% |
| Thomas Gleixner | 4 | 0.96% | 1 | 4.55% |
| Denis V. Lunev | 3 | 0.72% | 1 | 4.55% |
| Randy Dunlap | 2 | 0.48% | 1 | 4.55% |
| Cory Watson | 2 | 0.48% | 1 | 4.55% |
| Adrian Bunk | 1 | 0.24% | 1 | 4.55% |
| Greg Kroah-Hartman | 1 | 0.24% | 1 | 4.55% |
| Paul Gortmaker | 1 | 0.24% | 1 | 4.55% |
| Helge Deller | 1 | 0.24% | 1 | 4.55% |
| Total | 418 | 100.00% | 22 | 100.00% |
Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.