diff options
author | Dan Williams <dan.j.williams@intel.com> | 2008-04-21 10:51:07 -0700 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2008-07-21 21:54:40 -0700 |
commit | e105b8bfc769b0545b6f0f395179d1e43cbee822 (patch) | |
tree | 23a1f0839547829c4ca6e89cd40adf285eb9feb6 /drivers/base/core.c | |
parent | 93ded9b8fd42abe2c3607097963d8de6ad9117eb (diff) | |
download | op-kernel-dev-e105b8bfc769b0545b6f0f395179d1e43cbee822.zip op-kernel-dev-e105b8bfc769b0545b6f0f395179d1e43cbee822.tar.gz |
sysfs: add /sys/dev/{char,block} to lookup sysfs path by major:minor
Why?:
There are occasions where userspace would like to access sysfs
attributes for a device but it may not know how sysfs has named the
device or the path. For example what is the sysfs path for
/dev/disk/by-id/ata-ST3160827AS_5MT004CK? With this change a call to
stat(2) returns the major:minor then userspace can see that
/sys/dev/block/8:32 links to /sys/block/sdc.
What are the alternatives?:
1/ Add an ioctl to return the path: Doable, but sysfs is meant to reduce
the need to proliferate ioctl interfaces into the kernel, so this
seems counter productive.
2/ Use udev to create these symlinks: Also doable, but it adds a
udev dependency to utilities that might be running in a limited
environment like an initramfs.
3/ Do a full-tree search of sysfs.
[kay.sievers@vrfy.org: fix duplicate registrations]
[kay.sievers@vrfy.org: cleanup suggestions]
Cc: Neil Brown <neilb@suse.de>
Cc: Tejun Heo <htejun@gmail.com>
Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Reviewed-by: SL Baur <steve@xemacs.org>
Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Acked-by: Mark Lord <lkml@rtr.ca>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/base/core.c')
-rw-r--r-- | drivers/base/core.c | 83 |
1 files changed, 82 insertions, 1 deletions
diff --git a/drivers/base/core.c b/drivers/base/core.c index ee0a51a..be9aba4 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -27,6 +27,9 @@ int (*platform_notify)(struct device *dev) = NULL; int (*platform_notify_remove)(struct device *dev) = NULL; +static struct kobject *dev_kobj; +struct kobject *sysfs_dev_char_kobj; +struct kobject *sysfs_dev_block_kobj; #ifdef CONFIG_BLOCK static inline int device_is_not_partition(struct device *dev) @@ -776,6 +779,54 @@ int dev_set_name(struct device *dev, const char *fmt, ...) EXPORT_SYMBOL_GPL(dev_set_name); /** + * device_to_dev_kobj - select a /sys/dev/ directory for the device + * @dev: device + * + * By default we select char/ for new entries. Setting class->dev_obj + * to NULL prevents an entry from being created. class->dev_kobj must + * be set (or cleared) before any devices are registered to the class + * otherwise device_create_sys_dev_entry() and + * device_remove_sys_dev_entry() will disagree about the the presence + * of the link. + */ +static struct kobject *device_to_dev_kobj(struct device *dev) +{ + struct kobject *kobj; + + if (dev->class) + kobj = dev->class->dev_kobj; + else + kobj = sysfs_dev_char_kobj; + + return kobj; +} + +static int device_create_sys_dev_entry(struct device *dev) +{ + struct kobject *kobj = device_to_dev_kobj(dev); + int error = 0; + char devt_str[15]; + + if (kobj) { + format_dev_t(devt_str, dev->devt); + error = sysfs_create_link(kobj, &dev->kobj, devt_str); + } + + return error; +} + +static void device_remove_sys_dev_entry(struct device *dev) +{ + struct kobject *kobj = device_to_dev_kobj(dev); + char devt_str[15]; + + if (kobj) { + format_dev_t(devt_str, dev->devt); + sysfs_remove_link(kobj, devt_str); + } +} + +/** * device_add - add device to device hierarchy. * @dev: device. * @@ -829,6 +880,10 @@ int device_add(struct device *dev) error = device_create_file(dev, &devt_attr); if (error) goto ueventattrError; + + error = device_create_sys_dev_entry(dev); + if (error) + goto devtattrError; } error = device_add_class_symlinks(dev); @@ -873,6 +928,9 @@ int device_add(struct device *dev) device_remove_class_symlinks(dev); SymlinkError: if (MAJOR(dev->devt)) + device_remove_sys_dev_entry(dev); + devtattrError: + if (MAJOR(dev->devt)) device_remove_file(dev, &devt_attr); ueventattrError: device_remove_file(dev, &uevent_attr); @@ -948,8 +1006,10 @@ void device_del(struct device *dev) device_pm_remove(dev); if (parent) klist_del(&dev->knode_parent); - if (MAJOR(dev->devt)) + if (MAJOR(dev->devt)) { + device_remove_sys_dev_entry(dev); device_remove_file(dev, &devt_attr); + } if (dev->class) { device_remove_class_symlinks(dev); @@ -1074,7 +1134,25 @@ int __init devices_init(void) devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL); if (!devices_kset) return -ENOMEM; + dev_kobj = kobject_create_and_add("dev", NULL); + if (!dev_kobj) + goto dev_kobj_err; + sysfs_dev_block_kobj = kobject_create_and_add("block", dev_kobj); + if (!sysfs_dev_block_kobj) + goto block_kobj_err; + sysfs_dev_char_kobj = kobject_create_and_add("char", dev_kobj); + if (!sysfs_dev_char_kobj) + goto char_kobj_err; + return 0; + + char_kobj_err: + kobject_put(sysfs_dev_block_kobj); + block_kobj_err: + kobject_put(dev_kobj); + dev_kobj_err: + kset_unregister(devices_kset); + return -ENOMEM; } EXPORT_SYMBOL_GPL(device_for_each_child); @@ -1447,4 +1525,7 @@ void device_shutdown(void) dev->driver->shutdown(dev); } } + kobject_put(sysfs_dev_char_kobj); + kobject_put(sysfs_dev_block_kobj); + kobject_put(dev_kobj); } |