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    SubjectRe: [PATCH RFC/RFT v3 1/9] drivers: base: add new class "cpu" to group cpu devices
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    Hi Greg,

    On Sat, Mar 1, 2014 at 12:42 AM, Greg Kroah-Hartman
    <gregkh@linuxfoundation.org> wrote:
    > On Wed, Feb 19, 2014 at 04:06:08PM +0000, Sudeep Holla wrote:
    >> From: Sudeep Holla <sudeep.holla@arm.com>
    >>
    >> This patch creates a new class called "cpu" and assigns it to all the
    >> cpu devices. This helps in grouping all the cpu devices and associated
    >> child devices under the same class.
    >>
    >> This patch also:
    >> 1. modifies the get_parent_device to return the legacy path
    >> (/sys/devices/system/cpu/..) for the cpu class devices to support
    >> existing sysfs ABI
    >> 2. avoids creating link in the class directory pointing to the device as
    >> there would be per-cpu instance of these devices with the same name
    >> 3. makes sure subsystem symlink continues pointing to cpu bus instead of
    >> cpu class for cpu devices
    >>
    >> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
    >> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    >
    > Does the sysfs layout change at all with this patch applied?
    >

    No change to the existing layout, it just adds new entries, e.g. device symlink.

    Before this patch:
    / # ls /sys/devices/system/cpu/cpu0/ -l
    total 0
    drwxr-xr-x 5 root 0 0 Jan 1 00:02 cpuidle
    -rw-r--r-- 1 root 0 4096 Jan 1 00:02 online
    drwxr-xr-x 2 root 0 0 Jan 1 00:02 power
    lrwxrwxrwx 1 root 0 0 Jan 1 00:02 subsystem ->
    ../../../../bus/cpu
    drwxr-xr-x 2 root 0 0 Jan 1 00:02 topology
    -rw-r--r-- 1 root 0 4096 Jan 1 00:02 uevent

    After this patch:
    /sys/class/cpu # ls /sys/devices/system/cpu/cpu0 -l
    total 0
    drwxr-xr-x 6 root 0 0 Jan 1 00:00 cache
    drwxr-xr-x 5 root 0 0 Jan 1 00:00 cpuidle
    lrwxrwxrwx 1 root 0 0 Jan 1 00:00 device -> ../../cpu
    -rw-r--r-- 1 root 0 4096 Jan 1 00:00 online
    drwxr-xr-x 2 root 0 0 Jan 1 00:00 power
    lrwxrwxrwx 1 root 0 0 Jan 1 00:00 subsystem ->
    ../../../../bus/cpu
    drwxr-xr-x 2 root 0 0 Jan 1 00:00 topology
    -rw-r--r-- 1 root 0 4096 Jan 1 00:00 uevent

    Regards,
    Sudeep


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