As promised long ago, here is a patch to make sysfs optional. Note that
this will result in an un-bootable system if you're booting from a hard
drive. However, for *really* embedded systems, it will save a significant
amount of memory during runtime. And, it saves 4k from the built kernel
image for me.

	Pat

===== fs/Kconfig 1.39 vs edited =====


---

 fs/Kconfig            |   24 ++++++++++++++
 fs/Makefile           |    2 -
 fs/namespace.c        |    8 ++++
 include/linux/sysfs.h |   83 +++++++++++++++++++++++++++++++++++++++++++++-----
 4 files changed, 108 insertions(+), 9 deletions(-)

diff -puN fs/Kconfig~CONFIG_SYSFS fs/Kconfig
--- 25/fs/Kconfig~CONFIG_SYSFS	2004-02-09 18:45:59.000000000 -0800
+++ 25-akpm/fs/Kconfig	2004-02-09 18:45:59.000000000 -0800
@@ -780,6 +780,30 @@ config PROC_KCORE
 	bool
 	default y if !ARM
 
+config SYSFS
+	bool "sysfs file system support" if EMBEDDED
+	default y
+	help
+	The sysfs filesystem is a virtual filesystem that the kernel uses to export
+	internal kernel objects, their attributes, and their relationships to one
+	another.
+
+	Users can use sysfs to ascertain useful information about the running kernel,
+	such as the devices the kernel has discovered on each bus and which driver
+	each is bound to. sysfs can also be used to tune devices and other kernel
+	subsystems.
+
+	Some system agents rely on the information in sysfs to operate. /sbin/hotplug
+	uses device and object attributes in sysfs to assist in delegating policy
+	decisions, like persistantly naming devices.
+
+	sysfs is currently needed by the block subsystem to mount the root partition.
+	Therefore, you MUST say Y if you're booting from a hard drive. If you use any
+	type of hotpluggable device, you'll also need sysfs for /sbin/hotplug support.
+
+	However, designers of embedded systems may want to say N here to conserve
+	space.
+
 config DEVFS_FS
 	bool "/dev file system support (OBSOLETE)"
 	depends on EXPERIMENTAL
diff -puN fs/Makefile~CONFIG_SYSFS fs/Makefile
--- 25/fs/Makefile~CONFIG_SYSFS	2004-02-09 18:45:59.000000000 -0800
+++ 25-akpm/fs/Makefile	2004-02-09 18:45:59.000000000 -0800
@@ -39,7 +39,7 @@ obj-$(CONFIG_QUOTACTL)		+= quota.o
 
 obj-$(CONFIG_PROC_FS)		+= proc/
 obj-y				+= partitions/
-obj-y				+= sysfs/
+obj-$(CONFIG_SYSFS)		+= sysfs/
 obj-y				+= devpts/
 
 obj-$(CONFIG_PROFILING)		+= dcookies.o
diff -puN fs/namespace.c~CONFIG_SYSFS fs/namespace.c
--- 25/fs/namespace.c~CONFIG_SYSFS	2004-02-09 18:45:59.000000000 -0800
+++ 25-akpm/fs/namespace.c	2004-02-09 18:45:59.000000000 -0800
@@ -24,7 +24,15 @@
 #include <asm/uaccess.h>
 
 extern int __init init_rootfs(void);
+
+#ifdef CONFIG_SYSFS
 extern int __init sysfs_init(void);
+#else
+static inline int sysfs_init(void)
+{
+	return 0;
+}
+#endif
 
 /* spinlock for vfsmount related operations, inplace of dcache_lock */
 spinlock_t vfsmount_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
diff -puN include/linux/sysfs.h~CONFIG_SYSFS include/linux/sysfs.h
--- 25/include/linux/sysfs.h~CONFIG_SYSFS	2004-02-09 18:45:59.000000000 -0800
+++ 25-akpm/include/linux/sysfs.h	2004-02-09 18:45:59.000000000 -0800
@@ -18,6 +18,12 @@ struct attribute {
 	mode_t			mode;
 };
 
+struct attribute_group {
+	char			* name;
+	struct attribute	** attrs;
+};
+
+
 struct bin_attribute {
 	struct attribute	attr;
 	size_t			size;
@@ -25,14 +31,13 @@ struct bin_attribute {
 	ssize_t (*write)(struct kobject *, char *, loff_t, size_t);
 };
 
-int sysfs_create_bin_file(struct kobject * kobj, struct bin_attribute * attr);
-int sysfs_remove_bin_file(struct kobject * kobj, struct bin_attribute * attr);
-
 struct sysfs_ops {
 	ssize_t	(*show)(struct kobject *, struct attribute *,char *);
 	ssize_t	(*store)(struct kobject *,struct attribute *,const char *, size_t);
 };
 
+#ifdef CONFIG_SYSFS
+
 extern int
 sysfs_create_dir(struct kobject *);
 
@@ -57,13 +62,75 @@ sysfs_create_link(struct kobject * kobj,
 extern void
 sysfs_remove_link(struct kobject *, char * name);
 
-
-struct attribute_group {
-	char			* name;
-	struct attribute	** attrs;
-};
+int sysfs_create_bin_file(struct kobject * kobj, struct bin_attribute * attr);
+int sysfs_remove_bin_file(struct kobject * kobj, struct bin_attribute * attr);
 
 int sysfs_create_group(struct kobject *, const struct attribute_group *);
 void sysfs_remove_group(struct kobject *, const struct attribute_group *);
 
+#else /* CONFIG_SYSFS */
+
+static inline int sysfs_create_dir(struct kobject * k)
+{
+	return 0;
+}
+
+static inline void sysfs_remove_dir(struct kobject * k)
+{
+	;
+}
+
+static inline void sysfs_rename_dir(struct kobject * k, const char *new_name)
+{
+	;
+}
+
+static inline int sysfs_create_file(struct kobject * k, const struct attribute * a)
+{
+	return 0;
+}
+
+static inline int sysfs_update_file(struct kobject * k, const struct attribute * a)
+{
+	return 0;
+}
+
+static inline void sysfs_remove_file(struct kobject * k, const struct attribute * a)
+{
+	;
+}
+
+static inline int sysfs_create_link(struct kobject * k, struct kobject * t, char * n)
+{
+	return 0;
+}
+
+static inline void sysfs_remove_link(struct kobject * k, char * name)
+{
+	;
+}
+
+
+static inline int sysfs_create_bin_file(struct kobject * k, struct bin_attribute * a)
+{
+	return 0;
+}
+
+static inline int sysfs_remove_bin_file(struct kobject * k, struct bin_attribute * a)
+{
+	return 0;
+}
+
+static inline int sysfs_create_group(struct kobject * k, const struct attribute_group *g)
+{
+	return 0;
+}
+
+static inline void sysfs_remove_group(struct kobject * k, const struct attribute_group * g)
+{
+	;
+}
+
+#endif /* CONFIG_SYSFS */
+
 #endif /* _SYSFS_H_ */

_