1 files changed, 37 insertions, 0 deletions
diff --git a/kernel/graphics/mbox.c b/kernel/graphics/mbox.c
new file mode 100644
index 0000000..0dac497
--- /dev/null
+++ b/kernel/graphics/mbox.c
@@ -0,0 +1,37 @@
+#include <symbols.h>
+
+/* mailbox message buffer */
+volatile unsigned int  __attribute__((aligned(16))) mbox[36];
+
+#define VIDEOCORE_MBOX  (MMIO_BASE+0x0000B880)
+#define MBOX_READ       ((volatile unsigned int*)(VIDEOCORE_MBOX+0x0))
+#define MBOX_POLL       ((volatile unsigned int*)(VIDEOCORE_MBOX+0x10))
+#define MBOX_SENDER     ((volatile unsigned int*)(VIDEOCORE_MBOX+0x14))
+#define MBOX_STATUS     ((volatile unsigned int*)(VIDEOCORE_MBOX+0x18))
+#define MBOX_CONFIG     ((volatile unsigned int*)(VIDEOCORE_MBOX+0x1C))
+#define MBOX_WRITE      ((volatile unsigned int*)(VIDEOCORE_MBOX+0x20))
+#define MBOX_RESPONSE   0x80000000
+#define MBOX_FULL       0x80000000
+#define MBOX_EMPTY      0x40000000
+
+/**
+ * Make a mailbox call. Returns 0 on failure, non-zero on success
+ */
+int mbox_call(unsigned char ch)
+{
+    unsigned int r = (((unsigned int)((unsigned long)&mbox)&~0xF) | (ch&0xF));
+    /* wait until we can write to the mailbox */
+    do{asm volatile("nop");}while(*MBOX_STATUS & MBOX_FULL);
+    /* write the address of our message to the mailbox with channel identifier */
+    *MBOX_WRITE = r;
+    /* now wait for the response */
+    while(1) {
+        /* is there a response? */
+        do{asm volatile("nop");}while(*MBOX_STATUS & MBOX_EMPTY);
+        /* is it a response to our message? */
+        if(r == *MBOX_READ)
+            /* is it a valid successful response? */
+            return mbox[1]==MBOX_RESPONSE;
+    }
+    return 0;
+}