1 files changed, 99 insertions, 0 deletions
diff --git a/linux/src/kernel/dma.c b/linux/src/kernel/dma.c
new file mode 100644
index 0000000..724d8ca
--- /dev/null
+++ b/linux/src/kernel/dma.c
@@ -0,0 +1,99 @@
+/* $Id: dma.c,v 1.1 1999/04/26 05:58:29 tb 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 <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.
+ */
+
+
+
+/* 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 */