From 1dd236753c1245be97d305ea8cf38807ac62965b Mon Sep 17 00:00:00 2001
From: F5OEO <evaristec@gmail.com>
Date: Fri, 18 Dec 2015 08:43:06 +0000
Subject: [PATCH] Mailbox kernel compatible

---
 src/mailbox.c | 35 +++++++++++++++++++++++------------
 src/mailbox.h |  8 +++++---
 2 files changed, 28 insertions(+), 15 deletions(-)

diff --git a/src/mailbox.c b/src/mailbox.c
index a6efe07..a1d0ad7 100644
--- a/src/mailbox.c
+++ b/src/mailbox.c
@@ -34,6 +34,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <stdint.h>
 #include <sys/mman.h>
 #include <sys/ioctl.h>
+#include <sys/stat.h>
 
 #include "mailbox.h"
 
@@ -246,18 +247,28 @@ unsigned execute_qpu(int file_desc, unsigned num_qpus, unsigned control, unsigne
 int mbox_open() {
    int file_desc;
 
-   // open a char device file used for communicating with kernel mbox driver
-   file_desc = open(VCIO_DEVICE_FILE_NAME, 0);
-   if (file_desc < 0) {
-       printf("Can't open device file: %s\n", CUSTOM_DEVICE_FILE_NAME);
-       printf("Try %s\n", CUSTOM_DEVICE_FILE_NAME);
-	   file_desc = open(CUSTOM_DEVICE_FILE_NAME, 0);
-	   if (file_desc < 0) {
-	      printf("Can't open device file: %s\n", CUSTOM_DEVICE_FILE_NAME);
-	      printf("Try creating a device file with: sudo mknod %s c %d 0\n", CUSTOM_DEVICE_FILE_NAME, MAJOR_NUM);
-	      exit(-1);
-	   }
-   }
+    // Open a char device file used for communicating with kernel mbox driver.
+    file_desc = open(VCIO_DEVICE_FILE_NAME, 0);
+    if(file_desc >= 0) {
+        printf("Using mbox device " VCIO_DEVICE_FILE_NAME ".\n");
+        return file_desc;
+    }
+    
+    // Try to create one
+    unlink(LOCAL_DEVICE_FILE_NAME);
+    if(mknod(LOCAL_DEVICE_FILE_NAME, S_IFCHR|0600, makedev(MAJOR_NUM_A, 0)) >= 0 &&
+        (file_desc = open(LOCAL_DEVICE_FILE_NAME, 0)) >= 0) {
+        printf("Using local mbox device file with major %d.\n", MAJOR_NUM_A);
+        return file_desc;
+    }
+
+    unlink(LOCAL_DEVICE_FILE_NAME);
+    if(mknod(LOCAL_DEVICE_FILE_NAME, S_IFCHR|0600, makedev(MAJOR_NUM_B, 0)) >= 0 &&
+        (file_desc = open(LOCAL_DEVICE_FILE_NAME, 0)) >= 0) {
+        printf("Using local mbox device file with major %d.\n", MAJOR_NUM_B);
+        return file_desc;
+    }
+
 
    return file_desc;
 }
diff --git a/src/mailbox.h b/src/mailbox.h
index 20437f3..e76371a 100644
--- a/src/mailbox.h
+++ b/src/mailbox.h
@@ -26,10 +26,12 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
 #include <linux/ioctl.h>
+// Newer kernels (>= 4.1) use major 249, older ones major 100.
+#define MAJOR_NUM_A 249
+#define MAJOR_NUM_B 100
+#define IOCTL_MBOX_PROPERTY _IOWR(MAJOR_NUM_B, 0, char *)
 
-#define MAJOR_NUM 100
-#define IOCTL_MBOX_PROPERTY _IOWR(MAJOR_NUM, 0, char *)
-#define CUSTOM_DEVICE_FILE_NAME "/dev/rpidatv-mb"
+#define LOCAL_DEVICE_FILE_NAME "/dev/rpidatv-mb"
 #define VCIO_DEVICE_FILE_NAME "/dev/vcio"
 
 int mbox_open();