Name: Driverfs CPU Controls
Author: Rusty Russell
Status: Experimental
Depends: 
Depends: 
Depends: 

D: This adds an online element into the cpu driverfs entries, which
D: allows them to be brought on and offline.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .3214-linux-2.5.46/drivers/base/cpu.c .3214-linux-2.5.46.updated/drivers/base/cpu.c
--- .3214-linux-2.5.46/drivers/base/cpu.c	2002-11-05 10:54:25.000000000 +1100
+++ .3214-linux-2.5.46.updated/drivers/base/cpu.c	2002-11-05 16:34:11.000000000 +1100
@@ -26,6 +26,50 @@ struct device_driver cpu_driver = {
 	.devclass	= &cpu_devclass,
 };
 
+static ssize_t show_online(struct device *dev,
+			   char *buf,
+			   size_t count,
+			   loff_t off)
+{
+	char out[3];
+	struct cpu *cpu = container_of(container_of(dev,struct sys_device,dev),
+				       struct cpu, sysdev);
+
+	sprintf(out, "%i\n", !!cpu_online(cpu->sysdev.id));
+	if (off >= strlen(out)) return 0;
+	if (off + count > strlen(out)) count = strlen(out) - off;
+	memcpy(buf, out+off, count);
+	return (ssize_t)count;
+}
+
+static ssize_t store_online(struct device *dev,
+			    const char *buf,
+			    size_t count,
+			    loff_t off)
+{
+	struct cpu *cpu = container_of(container_of(dev,struct sys_device,dev),
+				       struct cpu, sysdev);
+	ssize_t ret;
+
+	if (off != 0)
+		return -EINVAL;
+	switch (buf[0]) {
+	case '0':
+		ret = cpu_down(cpu->sysdev.id);
+		break;
+	case '1':
+		ret = cpu_up(cpu->sysdev.id);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	if (ret == 0)
+		ret = count;
+	return ret;
+}
+
+static DEVICE_ATTR(online, 0600, show_online, store_online);
 
 /*
  * register_cpu - Setup a driverfs device for a CPU.
@@ -35,6 +79,8 @@ struct device_driver cpu_driver = {
  */
 int __init register_cpu(struct cpu *cpu, int num, struct node *root)
 {
+	int ret;
+
 	cpu->node_id = __cpu_to_node(num);
 	cpu->sysdev.name = "cpu";
 	cpu->sysdev.id = num;
@@ -42,7 +88,13 @@ int __init register_cpu(struct cpu *cpu,
 		cpu->sysdev.root = &root->sysroot;
 	snprintf(cpu->sysdev.dev.name, DEVICE_NAME_SIZE, "CPU %u", num);
 	cpu->sysdev.dev.driver = &cpu_driver;
-	return sys_device_register(&cpu->sysdev);
+	ret = sys_device_register(&cpu->sysdev);
+	if (ret < 0)
+		return ret;
+	ret = device_create_file(&cpu->sysdev.dev, &dev_attr_online);
+	if (ret < 0)
+		sys_device_unregister(&cpu->sysdev);
+	return ret;
 }
 
 
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .3214-linux-2.5.46/include/linux/cpu.h .3214-linux-2.5.46.updated/include/linux/cpu.h
--- .3214-linux-2.5.46/include/linux/cpu.h	2002-11-05 10:54:28.000000000 +1100
+++ .3214-linux-2.5.46.updated/include/linux/cpu.h	2002-11-05 16:32:32.000000000 +1100
@@ -21,6 +21,7 @@
 
 #include <linux/device.h>
 #include <linux/node.h>
+#include <asm/semaphore.h>
 
 struct cpu {
 	int node_id;		/* The node which contains the CPU */
@@ -29,4 +30,9 @@ struct cpu {
 
 extern int register_cpu(struct cpu *, int, struct node *);
 
+/* Bring a CPU up and take it down: grab semaphore to stop it. */
+extern struct semaphore cpucontrol;
+int cpu_up(unsigned int cpu);
+int cpu_down(unsigned int cpu);
+
 #endif /* _LINUX_CPU_H_ */
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .3214-linux-2.5.46/include/linux/smp.h .3214-linux-2.5.46.updated/include/linux/smp.h
--- .3214-linux-2.5.46/include/linux/smp.h	2002-10-15 15:19:44.000000000 +1000
+++ .3214-linux-2.5.46.updated/include/linux/smp.h	2002-11-05 16:32:32.000000000 +1100
@@ -76,8 +76,6 @@ struct notifier_block;
 /* Need to know about CPUs going up/down? */
 extern int register_cpu_notifier(struct notifier_block *nb);
 extern void unregister_cpu_notifier(struct notifier_block *nb);
-
-int cpu_up(unsigned int cpu);
 #else /* !SMP */
 
 /*
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .3214-linux-2.5.46/init/main.c .3214-linux-2.5.46.updated/init/main.c
--- .3214-linux-2.5.46/init/main.c	2002-11-05 10:54:28.000000000 +1100
+++ .3214-linux-2.5.46.updated/init/main.c	2002-11-05 16:32:32.000000000 +1100
@@ -33,6 +33,7 @@
 #include <linux/workqueue.h>
 #include <linux/profile.h>
 #include <linux/rcupdate.h>
+#include <linux/cpu.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .3214-linux-2.5.46/kernel/cpu.c .3214-linux-2.5.46.updated/kernel/cpu.c
--- .3214-linux-2.5.46/kernel/cpu.c	2002-10-31 12:37:04.000000000 +1100
+++ .3214-linux-2.5.46.updated/kernel/cpu.c	2002-11-05 16:32:32.000000000 +1100
@@ -8,7 +8,7 @@
 #include <linux/notifier.h>
 #include <linux/sched.h>
 #include <linux/unistd.h>
-#include <asm/semaphore.h>
+#include <linux/cpu.h>
 
 /* This protects CPUs going up and down... */
 DECLARE_MUTEX(cpucontrol);
@@ -26,7 +26,7 @@ void unregister_cpu_notifier(struct noti
 	notifier_chain_unregister(&cpu_chain,nb);
 }
 
-int __devinit cpu_up(unsigned int cpu)
+int cpu_up(unsigned int cpu)
 {
 	int ret;
 	void *hcpu = (void *)(long)cpu;
@@ -64,3 +64,9 @@ out:
 	up(&cpucontrol);
 	return ret;
 }
+
+int cpu_down(unsigned int cpu)
+{
+	/* Not Yet Implemented. */
+	return -ENOSYS;
+}