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    SubjectRe: [PATCH 5/9] perf: Adding sysfs group format attribute for pmu device
    On 01/27/2012 01:19 PM, Peter Zijlstra wrote:
    > On Fri, 2012-01-27 at 13:08 -0800, Corey Ashford wrote:
    >> s an example, the IBM PowerEN processor has roughly 20 different PMU's
    >> on it. Some of those PMU's are quite complex and divide their events up
    >> into subsets, each with different fields. For example, some events may
    >> have a PID matching field, and others may have an bus number matching
    >> field, or matching mode field, etc. The fields are different widths,
    >> and may overlap in the config/1/2 space.
    >> It seems that there are two approaches you could take:
    >> 1) Keep your format, but allow the fields to overlap in the bit space.
    >> For example:
    >> "/sys/...<dev>/format/event" contains "config:0-7"
    >> "/sys/...<dev>/format/pidmatch" contains "config:8-15"
    >> "/sys/...<dev>/format/busmatch" contains "config:8-13"
    >> Note that busmatch overlaps pidmatch
    >> 2) Create event groups that have their overlapping config space
    >> separated out:
    >> "/sys/...<dev>/format/event" contains "config:0-7"
    >> "/sys/...<dev>.1/format/pidmatch" contains "config:8-15"
    >> "/sys/...<dev>.2/format/busmatch" contains "config:8-13"
    >> Notice the .1 and .2 on the <dev>.
    >> This might help the user understand which fields go together. I'm not
    >> sold on the .1 syntax... you could do it as <dev>.<event-group-name>/ or
    >> <dev>/<event-group-name>/... or whatever seems to make the most sense
    >> and is relatively easy to implement and use.
    > Why try and stuff those 20 in a single driver? Have 20 drivers and each
    > their own format/ hierarchy.

    I'm sure that could work. Since sysfs seems to be fairly independent
    (if necessary) of the hardware structure, I suppose this wouldn't be a

    What do you think of Jiri's (Jirka's ?) other ideas of subdividing the
    format directory?

    - Corey

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