[Xen-devel] [PATCH] make blktap find it's major through sysfs

[Steven Rostedt <srostedt@xxxxxxxxxx>]

This patch makes blktap find it's major number by searching sysfs 
instead of reading /proc/devices.
-- Steve

Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>

diff -r f4ec8ed65c15 tools/blktap/drivers/blktapctrl.c
--- a/tools/blktap/drivers/blktapctrl.c Thu Sep 28 21:41:44 2006 -0400
+++ b/tools/blktap/drivers/blktapctrl.c Thu Sep 28 21:54:10 2006 -0400
@@ -636,28 +636,56 @@ static void print_drivers(void)
                DPRINTF("Found driver: [%s]\n",dtypes[i]->name);
 } 
 
+#define MTAB "/proc/mounts"
+#define BLKTAP_SYSFS_PATH "/class/xen/blktap0/dev"
+
+#define MAX_PATH 255
+#define _STR(x) #x
+#define STR(x) _STR(x)
+
+static char sysfsdir[MAX_PATH + 1];
+
+static int find_sysfsdir(void)
+{
+    FILE *fp;
+    char type[MAX_PATH + 1];
+
+    if ((fp = fopen(MTAB, "r")) == NULL)
+        return -1;
+
+    while (fscanf(fp, "%*s %"
+                  STR(MAX_PATH)
+                  "s %"
+                  STR(MAX_PATH)
+                  "s %*s %*d %*d\n",
+                  sysfsdir, type) == 2) {
+        if (strncmp(type, "sysfs", 5) == 0)
+            break;
+    }
+    fclose(fp);
+
+    return strncmp(type, "sysfs", 5) == 0 ? 0 : -1;
+}
+
 static int find_blktap_major(void)
 {
-       FILE *fp;
-       int major;
-       char device[256];
-
-       if ((fp = fopen("/proc/devices", "r")) == NULL)
-               return -1;
-
-       /* Skip title */
-       fscanf(fp,"%*s %*s\n");
-       while (fscanf(fp, "%d %255s\n", &major, device) == 2) {
-               if (strncmp("blktap", device, 6) == 0)
-                       break;
-       }
-
-       fclose(fp);
-
-       if (strncmp("blktap", device, 6) == 0)
-               return major;
-
-       return -1;
+    FILE *fp;
+    int major;
+    int minor;
+
+    if (find_sysfsdir() < 0)
+           return -1;
+    
+    strncat(sysfsdir, BLKTAP_SYSFS_PATH, MAX_PATH);
+    
+    if ((fp = fopen(sysfsdir, "r")) == NULL)
+           return -1;
+    
+    fscanf(fp,"%d:%d",&major, &minor);
+    
+    fclose(fp);
+    
+    return major;
 }
 
 int main(int argc, char *argv[])

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