Add optional dynamic assignment of tracing devices major nr

Setting FT_TASK_TRACE_MAJOR, LOG_MAJOR, FT_TRACE_MAJOR to 0
allows to have them automatically assigned by the kernel

4 files changed, 24 insertions, 7 deletions

diff --git a/litmus/ftdev.c b/litmus/ftdev.c
index 1c1c241a0a69..8b2d74d816a2 100644
--- a/litmus/ftdev.c
+++ b/litmus/ftdev.c
@@ -332,8 +332,15 @@ int register_ftdev(struct ftdev* ftdev, const char* name, int major)
         dev_t   trace_dev;
         int error = 0;
 
-        trace_dev = MKDEV(major, 0);
-        error     = register_chrdev_region(trace_dev, ftdev->minor_cnt, name);
+        if(major) {
+                trace_dev = MKDEV(major, 0);
+                error = register_chrdev_region(trace_dev, ftdev->minor_cnt,
+                                               name);
+        } else {
+                error = alloc_chrdev_region(&trace_dev, 0, ftdev->minor_cnt,
+                                name);
+                major = MAJOR(trace_dev);
+        }
         if (error)
         {
                 printk(KERN_WARNING "ftdev(%s): "
diff --git a/litmus/sched_task_trace.c b/litmus/sched_task_trace.c
index b7ea6d4e6e57..b59105110d7f 100644
--- a/litmus/sched_task_trace.c
+++ b/litmus/sched_task_trace.c
@@ -15,6 +15,8 @@
 #include <litmus/feather_trace.h>
 #include <litmus/ftdev.h>
 
+
+/* set MAJOR to 0 to have it dynamically assigned */
 #define FT_TASK_TRACE_MAJOR     253
 #define NO_EVENTS               4096 /* this is a buffer of 12 4k pages per CPU */
 
diff --git a/litmus/sched_trace.c b/litmus/sched_trace.c
index b2a71c4c6215..fcf6f44b0899 100644
--- a/litmus/sched_trace.c
+++ b/litmus/sched_trace.c
@@ -28,6 +28,8 @@
 /*
  * Major number for the tracing char device.
  * the major numbes are from the unassigned/local use block
+ *
+ * set MAJOR to 0 to have it dynamically assigned
  */
 #define LOG_MAJOR       251
 
@@ -328,14 +330,19 @@ static int __init register_buffer_dev(const char* name,
                                       struct file_operations* fops,
                                       int major, int count)
 {
-        dev_t  trace_dev;
+        dev_t trace_dev;
         struct cdev *cdev;
         int error = 0;
 
-        trace_dev = MKDEV(major, 0);
-        error = register_chrdev_region(trace_dev, count, name);
-        if (error)
-        {
+        if(major) {
+                trace_dev = MKDEV(major, 0);
+                error = register_chrdev_region(trace_dev, count, name);
+        } else {
+                /* dynamically allocate major number */
+                error = alloc_chrdev_region(&trace_dev, 0, count, name);
+                major = MAJOR(trace_dev);
+        }
+        if (error) {
                 printk(KERN_WARNING "sched trace: "
                        "Could not register major/minor number %d\n", major);
                 return error;
diff --git a/litmus/trace.c b/litmus/trace.c
index 5735d28f5e30..440376998dc9 100644
--- a/litmus/trace.c
+++ b/litmus/trace.c
@@ -70,6 +70,7 @@ feather_callback void save_timestamp_cpu(unsigned long event,
  */
 #define NO_TIMESTAMPS (2 << 11)
 
+/* set MAJOR to 0 to have it dynamically assigned */
 #define FT_TRACE_MAJOR  252
 
 static int alloc_timestamp_buffer(struct ftdev* ftdev, unsigned int idx)