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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>
20 lines
693 B
Text
20 lines
693 B
Text
What: /sys/dev
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Date: April 2008
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KernelVersion: 2.6.26
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Contact: Dan Williams <dan.j.williams@intel.com>
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Description: The /sys/dev tree provides a method to look up the sysfs
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path for a device using the information returned from
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stat(2). There are two directories, 'block' and 'char',
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beneath /sys/dev containing symbolic links with names of
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the form "<major>:<minor>". These links point to the
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corresponding sysfs path for the given device.
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Example:
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$ readlink /sys/dev/block/8:32
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../../block/sdc
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Entries in /sys/dev/char and /sys/dev/block will be
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dynamically created and destroyed as devices enter and
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leave the system.
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Users: mdadm <linux-raid@vger.kernel.org>
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