Re: export of SEQNUM to userspace

[Kay Sievers <kay.sievers@vrfy.org>]

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On Fri, Sep 03, 2004 at 11:22:03AM +0200, Kay Sievers wrote:
> On Fri, Sep 03, 2004 at 11:04:02AM +0200, Greg KH wrote:
> > On Fri, Sep 03, 2004 at 02:21:06AM +0200, Kay Sievers wrote:
> > > Something like this?
> > > 
> > > o /sys/kernel/hotplug_seqnum exports the current number
> > > o lib/kobject.c's  sequence_num is renamed to hotplug_seqnum and
> > >   exported by include/linux/kobject.h
> > > o the source file ksysfs.c in kernel/ creates on init the
> > >   sybsystem "/sys/kernel/" in sysfs
> > 
> > Nice, I like it.  How about this, smaller version instead.  I just
> > changed your code to use the __ATTR* macros and named a few variables a
> > bit better, no "g" variables for me :)
> > 
> > Is this ok with you?
> 
> Sure, looks perfect.

Oops, too fast. New patch. Forgot the unusal CONFIG_* combinations.

!CONFIG_SYSFS goes with:
  obj-$(CONFIG_SYSFS) += ksysfs.o

and
!CONFIG_HOTPLUG needs the ifdef's in ksysfs.c and kobject.h or is
there any better way?

Tested compilation of all four combinations and booted with:
CONFIG_SYSFS + !CONFIG_HOTPLUG.

Kay

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Add /sys/kernel subsystem to sysfs and export current hotplug SEQUNUM

o /sys/kernel/hotplug_seqnum exports the current number¶
o lib/kobject.c's  sequence_num is renamed to hotplug_seqnum and¶
  exported by include/linux/kobject.h¶
o the source file ksysfs.c in kernel/ creates on init the¶
  sybsystem "/sys/kernel/" in sysfs¶

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>

diff -Nru a/include/linux/kobject.h b/include/linux/kobject.h
--- a/include/linux/kobject.h	2004-09-03 15:12:57 +02:00
+++ b/include/linux/kobject.h	2004-09-03 15:12:57 +02:00
@@ -26,6 +26,11 @@
 
 #define KOBJ_NAME_LEN	20
 
+#ifdef CONFIG_HOTPLUG
+/* counter to tag the hotplug event, read only except for the kobject core */
+extern unsigned long hotplug_seqnum;
+#endif
+
 struct kobject {
 	char			* k_name;
 	char			name[KOBJ_NAME_LEN];
diff -Nru a/kernel/Makefile b/kernel/Makefile
--- a/kernel/Makefile	2004-09-03 15:12:57 +02:00
+++ b/kernel/Makefile	2004-09-03 15:12:57 +02:00
@@ -24,6 +24,7 @@
 obj-$(CONFIG_AUDIT) += audit.o
 obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
 obj-$(CONFIG_KPROBES) += kprobes.o
+obj-$(CONFIG_SYSFS) += ksysfs.o
 
 ifneq ($(CONFIG_IA64),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff -Nru a/kernel/ksysfs.c b/kernel/ksysfs.c
--- /dev/null	Wed Dec 31 16:00:00 196900
+++ b/kernel/ksysfs.c	2004-09-03 15:12:57 +02:00
@@ -0,0 +1,55 @@
+/*
+ * kernel/ksysfs.c - sysfs attributes in /sys/kernel, which
+ * 		     are not related to any other subsystem
+ *
+ * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
+ * 
+ * This file is released under the GPLv2
+ *
+ */
+
+#include <linux/config.h>
+#include <linux/kobject.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+#define KERNEL_ATTR_RO(_name) \
+static struct subsys_attribute _name##_attr = __ATTR_RO(_name)
+
+#define KERNEL_ATTR_RW(_name) \
+static struct subsys_attribute _name##_attr = \
+	__ATTR(_name, 0644, _name##_show, _name##_store)
+
+#ifdef CONFIG_HOTPLUG
+static ssize_t hotplug_seqnum_show(struct subsystem *subsys, char *page)
+{
+	return sprintf(page, "%lu\n", hotplug_seqnum);
+}
+KERNEL_ATTR_RO(hotplug_seqnum);
+#endif
+
+static decl_subsys(kernel, NULL, NULL);
+
+static struct attribute * kernel_attrs[] = {
+#ifdef CONFIG_HOTPLUG
+	&hotplug_seqnum_attr.attr,
+#endif
+	NULL
+};
+
+static struct attribute_group kernel_attr_group = {
+	.attrs = kernel_attrs,
+};
+
+static int __init ksysfs_init(void)
+{
+	int error = subsystem_register(&kernel_subsys);
+	if (!error)
+		error = sysfs_create_group(&kernel_subsys.kset.kobj, &kernel_attr_group);
+
+	return error;
+}
+
+core_initcall(ksysfs_init);
diff -Nru a/lib/kobject.c b/lib/kobject.c
--- a/lib/kobject.c	2004-09-03 15:12:57 +02:00
+++ b/lib/kobject.c	2004-09-03 15:12:57 +02:00
@@ -122,7 +122,7 @@
 
 #define BUFFER_SIZE	1024	/* should be enough memory for the env */
 #define NUM_ENVP	32	/* number of env pointers */
-static unsigned long sequence_num;
+unsigned long hotplug_seqnum;
 static spinlock_t sequence_lock = SPIN_LOCK_UNLOCKED;
 
 static void kset_hotplug(const char *action, struct kset *kset,
@@ -178,7 +178,7 @@
 	scratch += sprintf(scratch, "ACTION=%s", action) + 1;
 
 	spin_lock(&sequence_lock);
-	seq = sequence_num++;
+	seq = hotplug_seqnum++;
 	spin_unlock(&sequence_lock);
 
 	envp [i++] = scratch;