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    SubjectRe: [PATCH 06/20] Input: atmel_mxt_ts - allow writing to object sysfs entry
    Daniel Kurtz wrote:
    > Userspace can write a 24-bit value (encoded as a 6 character hex string)
    > to the 'object' sysfs entry to modify a single byte of the object table.
    > The hex string encodes a 3 bytes, in the following format:
    > TTFFVV
    > Where:
    > TT = object type
    > FF = object offset
    > VV = byte value
    > The object table is modified in device ram, which means the change is
    > volatile, and will be overwritten on the next device reset. To make
    > changes permanent, the new settings should be persisted in the device's
    > Non-Voltatile Memory using the updatenv sysfs entry.
    > Also, since the device driver initializes itself by reading some values
    > from the object table, the entire driver may need to be unloaded and
    > reloaded after writing the values for the driver to stay in sync. Whether
    > this is required depends on exactly which values were updated.
    > Signed-off-by: Daniel Kurtz <>

    NAK. I have several concerns about this:

    1) The object sysfs entry doesn't follow the sysfs guidelines, this is
    abusing it further.
    2) Object type can be larger than 1 byte in the future.
    3) Your interface restricts you to doing 1 byte writes. What about larger
    block sizes?

    In short, I think exposing the entire register space as a binary attribute
    (the same way that regmap does) is a preferable solution to this
    requirement, and we already have user space tools which use it.


    Nick Dyer
    Software Engineer, ITDev Ltd
    Hardware and Software Development Consultancy

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