summaryrefslogtreecommitdiff
path: root/kernel/dma.c
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /kernel/dma.c
downloadlinux-sh-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'kernel/dma.c')
-rw-r--r--kernel/dma.c158
1 files changed, 158 insertions, 0 deletions
diff --git a/kernel/dma.c b/kernel/dma.c
new file mode 100644
index 000000000000..aef0a45b7893
--- /dev/null
+++ b/kernel/dma.c
@@ -0,0 +1,158 @@
+/* $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);