1 files changed, 109 insertions, 0 deletions
diff --git a/linux/dev/kernel/dma.c b/linux/dev/kernel/dma.c
new file mode 100644
index 0000000..4b56978
--- /dev/null
+++ b/linux/dev/kernel/dma.c
@@ -0,0 +1,109 @@
+/* $Id: dma.c,v 1.1 1999/04/26 05:49:35 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]
+ */
+
+#define MACH_INCLUDE
+#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 }
+};
+
+#ifndef MACH
+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 += linux_sprintf (buf+len, "%2d: %s\n",
+				i,
+				dma_chan_busy[i].device_id);
+	}
+    }
+  return len;
+} /* get_dma_list */
+#endif
+
+int
+request_dma (unsigned int dmanr, const char *device_id)
+{
+  if (dmanr >= MAX_DMA_CHANNELS)
+    return -LINUX_EINVAL;
+  
+  if (xchg (&dma_chan_busy[dmanr].lock, 1) != 0)
+    return -LINUX_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 */