Re: [PATCH] DevFS support for /dev/cpu/X/(cpuid|msr)

["Ishan Jayawardena" <ioshadij@hotmail.com>]

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Perhaps this will suit your taste better...

I'd love to extend this work to support Paul Russell's hotplug cpu work, but 
I have absolutely no way at present to test it. (If some kind party would 
like to donate a quad pentium 4 Xeon with hotplug cpu support, I'll be more 
than happy to do so ;)

This is against 2.4.18-pre9-ac4 with devfs v199.9

Relevent comments, advise, improvisations, flames, welcome.

I. O. Jayawardena
.



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--- linux/fs/devfs/base.c	Mon Feb 18 16:07:49 2002
+++ linux-ioj/fs/devfs/base.c	Mon Feb 18 12:45:42 2002
@@ -631,6 +631,7 @@
 #include <linux/init.h>
 #include <linux/devfs_fs.h>
 #include <linux/devfs_fs_kernel.h>
+#include <linux/threads.h>
 #include <linux/smp_lock.h>
 #include <linux/smp.h>
 #include <linux/version.h>
@@ -1624,6 +1625,72 @@ devfs_handle_t devfs_register (devfs_han
 
 
 /**
+ * 	devfs_register_per_cpu - register a device node across all 
+ *		cpu-specific directories.
+ *	@leafname - the name of the device node
+ *
+ *	All other parameters are for devfs_register(). Returns zero on success.
+ */
+
+int devfs_register_per_cpu (const char *leafname, unsigned int flags, 
+			unsigned int major, unsigned int minor_start,
+			umode_t mode, void *ops, void *info)
+{
+    int i;
+    char *name;
+    char tmp[5] = { "0" }; /* FIXME: this string may overflow, but we don't know
+			the sizeof smp_num_cpus until we get it into a string */
+
+    if (smp_num_cpus > 1) sprintf (tmp, "%d", smp_num_cpus - 1);
+    name = kmalloc (strlen (leafname) + strlen (tmp) + sizeof (char) * 6, 
+			GFP_KERNEL);
+    if (!name) return -ENOMEM;
+    for(i = 0; i < smp_num_cpus; i++) {
+	sprintf (name, "cpu/%d/%s", i, leafname);
+	if (!devfs_register (NULL, name, flags, major, minor_start + i, 
+					mode, ops, info)) {
+	    PRINTK ("(): devfs_register() failed.\n");
+	    kfree (name);
+	    return -EAGAIN;
+	}
+    }
+    kfree (name);
+    return 0;
+} /* End function devfs_register_per_cpu */
+
+
+/**
+ *	devfs_unregister_per_cpu - unregister a node across /dev/cpu/
+ *	@leafname - the name of the device node
+ *
+ *	Unregisters a number of nodes (probably registered with
+ *	devfs_register_per_cpu() )
+ */
+
+void devfs_unregister_per_cpu (const char *leafname)
+{
+    int i;
+    char *name;
+    char tmp[5] = { "0" };
+    devfs_handle_t dh;
+
+    if (smp_num_cpus > 1) sprintf (tmp, "%d", smp_num_cpus - 1);
+    name = kmalloc (strlen (leafname) + strlen (tmp) + sizeof (char) * 6,
+			GFP_KERNEL);
+    if (!name) return;
+    for (i = 0; i < smp_num_cpus; i++) {
+	sprintf (name, "cpu/%d/%s", i, leafname);
+	dh = _devfs_walk_path (NULL, name, strlen (name), 0);
+	if (!dh) {
+	    kfree (name);
+	    return;
+	}
+	devfs_unregister (dh);
+    }
+    kfree (name);
+} /* End function devfs_unregister_per_cpu */
+
+/**
  *	_devfs_unhook - Unhook a device entry from its parents list
  *	@de: The entry to unhook.
  *
@@ -2355,7 +2422,9 @@ __setup("devfs=", devfs_setup);
 
 EXPORT_SYMBOL(devfs_put);
 EXPORT_SYMBOL(devfs_register);
+EXPORT_SYMBOL(devfs_register_per_cpu);
 EXPORT_SYMBOL(devfs_unregister);
+EXPORT_SYMBOL(devfs_unregister_per_cpu);
 EXPORT_SYMBOL(devfs_mk_symlink);
 EXPORT_SYMBOL(devfs_mk_dir);
 EXPORT_SYMBOL(devfs_get_handle);
@@ -3172,6 +3241,17 @@ static int devfs_mknod (struct inode *di
 			  inode->i_uid, inode->i_gid, fs_info, 0);
     return 0;
 }   /*  End Function devfs_mknod  */
+
+void devfs_mk_dir_per_cpu (void)
+{
+    int i;
+    char name[7];
+
+    for (i = 0; i < smp_num_cpus; i++) {
+	sprintf (name, "cpu/%d", i);
+	devfs_mk_dir (NULL, name, NULL);
+    }
+}
 
 static int devfs_readlink (struct dentry *dentry, char *buffer, int buflen)
 {
--- linux/include/linux/devfs_fs_kernel.h	Mon Feb 18 16:05:21 2002
+++ linux-ioj/include/linux/devfs_fs_kernel.h	Mon Feb 18 14:08:38 2002
@@ -73,12 +73,17 @@ extern devfs_handle_t devfs_register (de
 				      unsigned int flags,
 				      unsigned int major, unsigned int minor,
 				      umode_t mode, void *ops, void *info);
+extern int devfs_register_per_cpu (const char *leafname, unsigned int flags,
+				   unsigned int major, unsigned int minor_start,
+				   umode_t mode, void *ops, void *info);
 extern void devfs_unregister (devfs_handle_t de);
+extern void devfs_unregister_per_cpu (const char *leafname);
 extern int devfs_mk_symlink (devfs_handle_t dir, const char *name,
 			     unsigned int flags, const char *link,
 			     devfs_handle_t *handle, void *info);
 extern devfs_handle_t devfs_mk_dir (devfs_handle_t dir, const char *name,
 				    void *info);
+extern void devfs_mk_dir_per_cpu (void);
 extern devfs_handle_t devfs_get_handle (devfs_handle_t dir, const char *name,
 					unsigned int major,unsigned int minor,
 					char type, int traverse_symlinks);
@@ -149,9 +154,20 @@ static inline devfs_handle_t devfs_regis
 {
     return NULL;
 }
+static inline int devfs_register_per_cpu (const char *name,
+					  unsigned int flags, 
+					  unsigned int major, 
+					  unsigned int minor_start,
+					  umode_t mode, void *ops, void *info);
+{
+    return NULL;
+}
 static inline void devfs_unregister (devfs_handle_t de)
 {
-    return;
+}
+static inline void devfs_unregister_per_cpu (const char *name)
+{
+    return NULL;
 }
 static inline int devfs_mk_symlink (devfs_handle_t dir, const char *name,
 				    unsigned int flags, const char *link,
@@ -163,6 +179,9 @@ static inline devfs_handle_t devfs_mk_di
 					   const char *name, void *info)
 {
     return NULL;
+}
+static inline void devfs_mk_dir_per_cpu (void)
+{
 }
 static inline devfs_handle_t devfs_get_handle (devfs_handle_t dir,
 					       const char *name,
--- linux/init/main.c	Mon Feb 18 16:07:37 2002
+++ linux-ioj/init/main.c	Sun Feb 17 23:26:43 2002
@@ -497,9 +497,13 @@ unsigned long wait_init_idle;
 static void __init smp_init(void)
 {
 	APIC_init_uniprocessor();
+
+	devfs_mk_dir_per_cpu();
 }
 #else
-#define smp_init()	do { } while (0)
+#define smp_init()	do { \
+		devfs_mk_dir_per_cpu(); \
+	} while (0)
 #endif
 
 #else
@@ -523,6 +527,8 @@ static void __init smp_init(void)
 		barrier();
 	}
 	printk("All processors have done init_idle\n");
+
+	devfs_mk_dir_per_cpu();
 }
 
 #endif
--- linux/arch/i386/kernel/cpuid.c	Thu Oct 11 12:04:57 2001
+++ linux-ioj/arch/i386/kernel/cpuid.c	Mon Feb 18 15:19:32 2002
@@ -32,6 +32,7 @@
 #include <linux/errno.h>
 #include <linux/fcntl.h>
 #include <linux/init.h>
+#include <linux/devfs_fs_kernel.h>
 #include <linux/poll.h>
 #include <linux/smp.h>
 #include <linux/major.h>
@@ -140,24 +141,26 @@ static struct file_operations cpuid_fops
   open:		cpuid_open,
 };
 
-int __init cpuid_init(void)
+static int __init cpuid_init(void)
 {
-  if (register_chrdev(CPUID_MAJOR, "cpu/cpuid", &cpuid_fops)) {
+  if (devfs_register_chrdev(CPUID_MAJOR, "cpu/%d/cpuid", &cpuid_fops)) {
     printk(KERN_ERR "cpuid: unable to get major %d for cpuid\n",
 	   CPUID_MAJOR);
     return -EBUSY;
   }
 
-  return 0;
+  return devfs_register_per_cpu("cpuid", DEVFS_FL_DEFAULT, CPUID_MAJOR, 0,
+		S_IFCHR | S_IRUSR | S_IRGRP, &cpuid_fops, NULL);
 }
 
 void __exit cpuid_exit(void)
 {
-  unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
+  devfs_unregister_chrdev(CPUID_MAJOR, "cpu/%d/cpuid");
+  devfs_unregister_per_cpu("cpuid");
 }
 
 module_init(cpuid_init);
-module_exit(cpuid_exit)
+module_exit(cpuid_exit);
 
 EXPORT_NO_SYMBOLS;
 
--- linux/arch/i386/kernel/msr.c	Thu Oct 11 12:04:57 2001
+++ linux-ioj/arch/i386/kernel/msr.c	Mon Feb 18 15:19:05 2002
@@ -31,6 +31,7 @@
 #include <linux/errno.h>
 #include <linux/fcntl.h>
 #include <linux/init.h>
+#include <linux/devfs_fs_kernel.h>
 #include <linux/poll.h>
 #include <linux/smp.h>
 #include <linux/major.h>
@@ -248,24 +249,26 @@ static struct file_operations msr_fops =
   open:		msr_open,
 };
 
-int __init msr_init(void)
+static int __init msr_init(void)
 {
-  if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
+  if (devfs_register_chrdev(MSR_MAJOR, "cpu/%d/msr", &msr_fops)) {
     printk(KERN_ERR "msr: unable to get major %d for msr\n",
 	   MSR_MAJOR);
     return -EBUSY;
   }
   
-  return 0;
+  return devfs_register_per_cpu("msr", DEVFS_FL_DEFAULT, MSR_MAJOR, 0,
+			S_IFCHR | S_IRUSR | S_IRGRP, &msr_fops, NULL);
 }
 
 void __exit msr_exit(void)
 {
-  unregister_chrdev(MSR_MAJOR, "cpu/msr");
+  devfs_unregister_chrdev(MSR_MAJOR, "cpu/%d/msr");
+  devfs_unregister_per_cpu("msr");
 }
 
 module_init(msr_init);
-module_exit(msr_exit)
+module_exit(msr_exit);
 
 EXPORT_NO_SYMBOLS;