From e105b8bfc769b0545b6f0f395179d1e43cbee822 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 21 Apr 2008 10:51:07 -0700 Subject: 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 Cc: Tejun Heo Acked-by: Kay Sievers Reviewed-by: SL Baur Acked-by: Kay Sievers Acked-by: Mark Lord Acked-by: H. Peter Anvin Signed-off-by: Dan Williams Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/devio.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'drivers/usb/core') 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) 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 -- cgit v1.2.3