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    Subject[PATCH v4 0/5] da850-evm: add gpio-{keys,leds} for UI and BB expanders
    The da850-evm baseboard (BB) and its UI board both have tca6416 IO expanders.
    They are bootstrapped to different I2C addresses so they can be used

    The expander on the UI board is currently used to enable/disable the
    peripherals that are available on the UI board. In addition to this
    functionality the expander is also connected to 8 pushbuttons. The expander
    on the baseboard is not currently used; it is connected to deep sleep enable,
    sw reset, a push button, some switches and LEDs.

    This proposed patch series enables the push buttons and switches on the UI and
    BB expanders using the gpio-keys polling mode patch by Alexander Clouter. Some
    work was performed to test irq-based gpio-keys support on the expanders (a WIP
    patch can be posted on request) but I believe that it is not possible to use
    irq-based gpio-keys on IO expanders for arm systems at this time.

    The attempt started when I noticed the patch of Alek Du and Alan Cox [1] which
    was recently committed [2]; a stab at integrating irq-based gpio-keys support
    based on that patch was attempted. I found that I either got a warning that the
    irq could not be mapped for the given gpio ; or, when N_IRQ was increased, a
    system freeze.

    From what I have read (particularly the message by Grant Likely [3]) IRQs on
    IO expanders are not ready in ARM yet. I _think_ that the sparse IRQ rework by
    Thomas Gleixner [4] will resolve the blocker to irq-based gpio-keys support.

    In the meantime we have buttons and switches that we would like to excersise
    in our prototyping development. The patch to convert this series to irq-based
    gpio-keys will be straighforward once the support in arch/arm is there.

    There is an existing tca6416-keypad driver with polling support which I did not
    employ because it isn't possible to keep the gpio's used for peripheral
    enable/disable on the UI board or the LEDs on the baseboard registered while
    simultaneously registering the pushbuttons or switches as a tca6416-keypad

    I tested this patch series using evtest on the resulting /dev/input/eventN
    devices and also on the event node of a non-polling gpio-keys instance to
    ensure that irq-based input handling is not broken by the introduction of the
    polling-mode gpio-keys patch. The non-polling instance creation and
    registration is not included in this series since it uses one of the boot-mode
    DIP switches and woult not (I think) be suitable for mainline.

    I'm not an expert in irq's or gpio-keys; this is, in fact, my first proposed
    feature. Please feel free to correct me -- I welcome the chance to learn from
    your expertise.


    Alexander Clouter (1):
    input: gpio_keys: polling mode support

    Ben Gardiner (4):
    da850-evm: add UI Expander pushbuttons
    da850-evm: extract defines for SEL{A,B,C} pins in UI expander
    da850-evm: add baseboard GPIO expander buttons, switches and LEDs
    da850-evm: KEYBOARD_GPIO and INPUT_POLLDEV Kconfig conditionals

    arch/arm/mach-davinci/Kconfig | 4 +
    arch/arm/mach-davinci/board-da850-evm.c | 312 +++++++++++++++++++++++++++++--
    drivers/input/keyboard/gpio_keys.c | 120 ++++++++++--
    include/linux/gpio_keys.h | 1 +
    4 files changed, 406 insertions(+), 31 deletions(-)


    Changes since v3:
    * introduced patch 5 in the series by extracting the Kconfig changes proposed
    in patch 2 of v3.
    * not gpio_request()'ing the sw_rst and deep_sleep_en lines as requested
    (Sekhar Nori)

    Changes since v2:
    * register a single input device for switches and keys on the baseboard since
    there is no benefit to separate devices with different polling intervals
    (Dmitry Torokhov)
    * use static array intialization and range intialization for platform data
    structure to minimize the amount of runtime intialization needed:
    (Sekhar Nori)
    * Use the da850_evm variable name prefix for static symbols in

    Changes since v1:
    * use locally defined functions that are no-ops/error checkers when
    INPUT_POLLDEV is not defined.
    * disable polling mode support when input-polldev is a module and gpio_keys
    is builtin
    * set INPUT_POLLDEV default for DA850_EVM machine, but don't select it
    * adding note to description about why tca6416-keypad was not used

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