Feather-Trace: register devices with sysfs

This patch implements support for Feather-Trace devices to use the sysfs
file system and, consequently, udev support.

This allows us to allocate major/minor numbers for Feather-Trace
devices dynamically, which is desirable because our old static
allocations tend to create conflicts on modern distributions and/or
when there are many cores.

1 files changed, 47 insertions, 18 deletions

diff --git a/litmus/ftdev.c b/litmus/ftdev.c
index 51dafaebf8a6..d68d05c6d7dc 100644
--- a/litmus/ftdev.c
+++ b/litmus/ftdev.c
@@ -4,6 +4,7 @@
 #include <linux/cdev.h>
 #include <asm/uaccess.h>
 #include <linux/module.h>
+#include <linux/device.h>
 
 #include <litmus/litmus.h>
 #include <litmus/feather_trace.h>
@@ -310,10 +311,11 @@ struct file_operations ftdev_fops = {
 };
 
 
-void ftdev_init(struct ftdev* ftdev, struct module* owner)
+void ftdev_init(struct ftdev* ftdev, struct module* owner, const char* name)
 {
-        int i;
+        int i, error;
         cdev_init(&ftdev->cdev, &ftdev_fops);
+        ftdev->name = name;
         ftdev->cdev.owner = owner;
         ftdev->cdev.ops = &ftdev_fops;
         ftdev->minor_cnt  = 0;
@@ -326,35 +328,62 @@ void ftdev_init(struct ftdev* ftdev, struct module* owner)
         ftdev->alloc    = NULL;
         ftdev->free     = NULL;
         ftdev->can_open = NULL;
+
+        ftdev->class = class_create(owner, ftdev->name);
+        if (IS_ERR(ftdev->class)) {
+                error = PTR_ERR(ftdev->class);
+                printk(KERN_WARNING "ftdev(%s): "
+                        "Could not create device class.\n",
+                        name);
+        }
 }
 
-int register_ftdev(struct ftdev* ftdev, const char* name, int major)
+int register_ftdev(struct ftdev* ftdev)
 {
+        struct device **device;
         dev_t   trace_dev;
-        int error = 0;
-
-        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);
-        }
+        int error = 0, major, i;
+
+        error = alloc_chrdev_region(&trace_dev, 0, ftdev->minor_cnt,
+                        ftdev->name);
+        major = MAJOR(trace_dev);
         if (error)
         {
                 printk(KERN_WARNING "ftdev(%s): "
                        "Could not register major/minor number %d/%u\n",
-                       name, major, ftdev->minor_cnt);
-                return error;
+                       ftdev->name, major, ftdev->minor_cnt);
+                goto out;
         }
         error = cdev_add(&ftdev->cdev, trace_dev, ftdev->minor_cnt);
         if (error) {
                 printk(KERN_WARNING "ftdev(%s): "
                        "Could not add cdev for major/minor = %d/%u.\n",
-                       name, major, ftdev->minor_cnt);
-                return error;
+                       ftdev->name, major, ftdev->minor_cnt);
+                goto out;
+        }
+
+        /*
+         * create all the minor devices
+         */
+        for (i = 0; i < ftdev->minor_cnt; ++i)
+        {
+                trace_dev = MKDEV(major, i);
+                device = &(ftdev->minor[i].device);
+
+                *device = device_create(ftdev->class, NULL, trace_dev, NULL,
+                                "%s%d", ftdev->name, i);
+                if (IS_ERR(*device)) {
+                        error = PTR_ERR(*device);
+                        printk(KERN_WARNING "ftdev(%s): "
+                                "Could not create device major/minor number "
+                                "%d/%d\n", ftdev->name, major, i);
+                        printk(KERN_WARNING "ftdev(%s): "
+                                "Will not continue creating devices. Tracing "
+                                "may be in an inconsistent state.\n",
+                                ftdev->name);
+                        goto out;
+                }
         }
+out:
         return error;
 }