* patch sysfs-add-sys-dev-char-block-to-lookup-sysfs-path-by-major-minor.patch added to gregkh-2.6 tree
[not found] <1208800267.26479.3.camel@dwillia2-linux.ch.intel.com>
@ 2008-04-28 23:51 ` gregkh
2008-04-29 7:48 ` SL Baur
0 siblings, 1 reply; 3+ messages in thread
From: gregkh @ 2008-04-28 23:51 UTC (permalink / raw)
To: dan.j.williams, akpm, gregkh, greg, hpa, htejun, kay.sievers,
linux-kernel, lkml, neilb, steve
This is a note to let you know that I've just added the patch titled
Subject: sysfs: add /sys/dev/{char,block} to lookup sysfs path by major:minor
to my gregkh-2.6 tree. Its filename is
sysfs-add-sys-dev-char-block-to-lookup-sysfs-path-by-major-minor.patch
This tree can be found at
http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/patches/
>From dan.j.williams@intel.com Mon Apr 21 10:51:11 2008
From: Dan Williams <dan.j.williams@intel.com>
Date: Mon, 21 Apr 2008 10:51:07 -0700
Subject: sysfs: add /sys/dev/{char,block} to lookup sysfs path by major:minor
To: Greg KH <greg@kroah.com>, Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Message-ID: <1208800267.26479.3.camel@dwillia2-linux.ch.intel.com>
From: Dan Williams <dan.j.williams@intel.com>
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>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: 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>
---
Documentation/ABI/testing/sysfs-dev | 20 ++++++++
Documentation/filesystems/sysfs.txt | 6 ++
block/genhd.c | 5 +-
drivers/base/class.c | 4 +
drivers/base/core.c | 83 +++++++++++++++++++++++++++++++++++-
drivers/usb/core/devio.c | 5 ++
include/linux/device.h | 3 +
7 files changed, 124 insertions(+), 2 deletions(-)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -360,7 +360,10 @@ static struct kobject *base_probe(dev_t
static int __init genhd_device_init(void)
{
- int error = class_register(&block_class);
+ int error;
+
+ block_class.dev_kobj = sysfs_dev_block_kobj;
+ error = class_register(&block_class);
if (unlikely(error))
return error;
bdev_map = kobj_map_init(base_probe, &block_class_lock);
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-dev
@@ -0,0 +1,20 @@
+What: /sys/dev
+Date: April 2008
+KernelVersion: 2.6.26
+Contact: Dan Williams <dan.j.williams@intel.com>
+Description: The /sys/dev tree provides a method to look up the sysfs
+ path for a device using the information returned from
+ stat(2). There are two directories, 'block' and 'char',
+ beneath /sys/dev containing symbolic links with names of
+ the form "<major>:<minor>". These links point to the
+ corresponding sysfs path for the given device.
+
+ Example:
+ $ readlink /sys/dev/block/8:32
+ ../../block/sdc
+
+ Entries in /sys/dev/char and /sys/dev/block will be
+ dynamically created and destroyed as devices enter and
+ leave the system.
+
+Users: mdadm <linux-raid@vger.kernel.org>
--- a/Documentation/filesystems/sysfs.txt
+++ b/Documentation/filesystems/sysfs.txt
@@ -248,6 +248,7 @@ The top level sysfs directory looks like
block/
bus/
class/
+dev/
devices/
firmware/
net/
@@ -274,6 +275,11 @@ fs/ contains a directory for some filesy
filesystem wanting to export attributes must create its own hierarchy
below fs/ (see ./fuse.txt for an example).
+dev/ contains two directories char/ and block/. Inside these two
+directories there are symlinks named <major>:<minor>. These symlinks
+point to the sysfs directory for the given device. /sys/dev provides a
+quick way to lookup the sysfs interface for a device from the result of
+a stat(2) operation.
More information can driver-model specific features can be found in
Documentation/driver-model/.
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -149,6 +149,10 @@ int class_register(struct class *cls)
if (error)
return error;
+ /* set the default /sys/dev directory for devices of this class */
+ if (!cls->dev_kobj)
+ cls->dev_kobj = sysfs_dev_char_kobj;
+
#if defined(CONFIG_SYSFS_DEPRECATED) && defined(CONFIG_BLOCK)
/* let the block class directory show up in the root of sysfs */
if (cls != &block_class)
--- 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)
@@ -761,6 +764,54 @@ static void device_remove_class_symlinks
}
/**
+ * 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.
*
@@ -810,6 +861,10 @@ 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);
@@ -854,6 +909,9 @@ 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);
@@ -929,8 +987,10 @@ 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);
@@ -1055,7 +1115,25 @@ 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);
@@ -1351,4 +1429,7 @@ void device_shutdown(void)
dev->driver->shutdown(dev);
}
}
+ kobject_put(sysfs_dev_char_kobj);
+ kobject_put(sysfs_dev_block_kobj);
+ kobject_put(dev_kobj);
}
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1748,6 +1748,11 @@ int __init usb_devio_init(void)
usb_classdev_class = NULL;
goto out;
}
+ /* devices of this class shadow the major:minor of their parent
+ * device, so clear ->dev_kobj to prevent adding duplicate entries
+ * to /sys/dev
+ */
+ usb_classdev_class->dev_kobj = NULL;
usb_register_notify(&usbdev_nb);
#endif
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -194,6 +194,7 @@ struct class {
struct semaphore sem; /* locks children, devices, interfaces */
struct class_attribute *class_attrs;
struct device_attribute *dev_attrs;
+ struct kobject *dev_kobj;
int (*dev_uevent)(struct device *dev, struct kobj_uevent_env *env);
@@ -206,6 +207,8 @@ struct class {
struct pm_ops *pm;
};
+extern struct kobject *sysfs_dev_block_kobj;
+extern struct kobject *sysfs_dev_char_kobj;
extern int __must_check class_register(struct class *class);
extern void class_unregister(struct class *class);
extern int class_for_each_device(struct class *class, void *data,
Patches currently in gregkh-2.6 which might be from dan.j.williams@intel.com are
driver-core/sysfs-add-sys-dev-char-block-to-lookup-sysfs-path-by-major-minor.patch
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