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    DateSat, 9 Jun 2007 09:42:57 +0200 (CEST)
    FromJan Engelhardt <>
    SubjectRe: Rules on how to use sysfs in userspace programs
    On Jun 8 2007 13:36, Greg KH wrote:
    >
    >Any comments or critique of this is greatly appreciated.
    >
    >------------------------------------
    >
    >Rules to access device-information in the Linux kernel sysfs
    >
    >The kernel exported sysfs exports internal kernel implementation-details
    >and depends on internal kernel-structures and layout. It is agreed upon
    >kernel developers, that the Linux kernel does not provide a stable
    >internal API.  As sysfs is a direct export of kernel internal
    >structures, the sysfs interface can't provide a stable interface too, it
    >may always change along with internal kernel changes.
    
    Perhaps use the full writing form of "can't", "don't", etc. for,
    well, written text?
    
    >- Hierarchy in a single device-tree
    >  There is only one valid place in sysfs where hierarchy can be examined
    >  and this is below: /sys/devices.
    >  It is planned, the all device directories will end up in the tree
       It is planned that all ...
    >  below this directory.
    >
    >- Classification by subsystem
    >  There are currently three places for classification of devices:
    >  /sys/block, /sys/class and /sys/bus. It is planned, that these will
    
    No commas before "that".
    
    >  not contain any device-directories themselves, but only flat lists of
    >  symlinks pointing to the unified /sys/devices tree.
    >
    >  All three places have completely different rules to access the
    >  information.  It is planned to merge all three
    >  classification-directories into one place at /sys/subsystem/,
    
    What about this future plan? If it is not going in soon or so, the paragraph
    should probably be left out.
    
    >  following the current layout of the bus-directories. All buses and
    >  classes, including the converted block-subsystemm, will show up
    >  there.
    >  The devices of a subsystem will create a symlink in the "devices"
    >  directory at /sys/subsystem/<name>/devices/.
    >
    >  It is planned to remove all these links when when all class-device
    >  directories live in /sys/devices.
    >
    
    
    	Jan
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