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authorDan Williams <dan.j.williams@intel.com>2008-04-21 13:51:07 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2008-07-22 00:54:40 -0400
commite105b8bfc769b0545b6f0f395179d1e43cbee822 (patch)
tree23a1f0839547829c4ca6e89cd40adf285eb9feb6 /drivers/usb
parent93ded9b8fd42abe2c3607097963d8de6ad9117eb (diff)
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/usb')
-rw-r--r--drivers/usb/core/devio.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 54a350ccd033..6fbc8f5ab80c 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1792,6 +1792,11 @@ int __init usb_devio_init(void)
1792 usb_classdev_class = NULL; 1792 usb_classdev_class = NULL;
1793 goto out; 1793 goto out;
1794 } 1794 }
1795 /* devices of this class shadow the major:minor of their parent
1796 * device, so clear ->dev_kobj to prevent adding duplicate entries
1797 * to /sys/dev
1798 */
1799 usb_classdev_class->dev_kobj = NULL;
1795 1800
1796 usb_register_notify(&usbdev_nb); 1801 usb_register_notify(&usbdev_nb);
1797#endif 1802#endif