From: Patrick Mochel <mochel@digitalimplant.org>
Here is a patch to make sysfs optional. Note that with CONFIG_SYSFS=n you
must specify the boot device's major:minor on the kernel boot command line
with
root=03:01
For embedded systems, it will save a significant amount of memory during
runtime. And, it saves 4k from the built kernel image for me.
---
25-akpm/fs/Kconfig | 24 ++++++++++++
25-akpm/fs/Makefile | 2 -
25-akpm/fs/namespace.c | 8 ++++
25-akpm/include/linux/sysfs.h | 83 +++++++++++++++++++++++++++++++++++++-----
25-akpm/init/do_mounts.c | 2 +
5 files changed, 110 insertions(+), 9 deletions(-)
diff -puN fs/Kconfig~CONFIG_SYSFS fs/Kconfig
--- 25/fs/Kconfig~CONFIG_SYSFS 2004-04-10 01:33:29.689986376 -0700
+++ 25-akpm/fs/Kconfig 2004-04-10 01:33:29.699984856 -0700
@@ -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 used by the block subsystem to mount the root
+ partition. If sysfs is disabled you must specify the boot device on
+ the kernel boot command line via its major and minor numbers. For
+ example, "root=03:01" for /dev/hda1.
+
+ Designers of embedded systems may wish 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 2004-04-10 01:33:29.690986224 -0700
+++ 25-akpm/fs/Makefile 2004-04-10 01:33:29.699984856 -0700
@@ -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 2004-04-10 01:33:29.691986072 -0700
+++ 25-akpm/fs/namespace.c 2004-04-10 01:33:29.700984704 -0700
@@ -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 2004-04-10 01:33:29.693985768 -0700
+++ 25-akpm/include/linux/sysfs.h 2004-04-10 01:33:29.701984552 -0700
@@ -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_ */
diff -puN init/do_mounts.c~CONFIG_SYSFS init/do_mounts.c
--- 25/init/do_mounts.c~CONFIG_SYSFS 2004-04-10 01:33:29.694985616 -0700
+++ 25-akpm/init/do_mounts.c 2004-04-10 01:33:29.701984552 -0700
@@ -141,9 +141,11 @@ dev_t __init name_to_dev_t(char *name)
dev_t res = 0;
int part;
+#ifdef CONFIG_SYSFS
sys_mkdir("/sys", 0700);
if (sys_mount("sysfs", "/sys", "sysfs", 0, NULL) < 0)
goto out;
+#endif
if (strncmp(name, "/dev/", 5) != 0) {
unsigned maj, min;
_