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    Subject[RFC] gpiolib: introduce descriptor-based GPIO interface
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    Just a RFC to check if the direction seems good before going onward with more
    serious work. This patch introduces a set of gpiod_* functions that work like
    their gpio_* counterparts, but use opaque descriptors instead of integers.

    The current integer-based GPIO namespace is bad because it allows GPIOs to be
    used without being properly allocated, and poses portability concerns with the
    maximum number of GPIOs of the system being a compile-time constant. Some
    implementation details could also be improved by an opaque handler, e.g. the
    GPIO descriptors could be moved from the current static array to a more flexible
    list of GPIO chips containing their own descriptors.

    With this patch GPIO handles can only be obtained by calling gpio_to_desc(),
    which converts a valid GPIO number to its descriptor - proper lookup functions
    that totally get rid of GPIO numbers are the next step if this first patch is
    received positively.

    This is only a first step towards a bigger gpiolib rework. Getting rid of the
    integer handles for GPIOs will allow us to continue on with the following:
    * Proper GPIO lookup functions a la regulator, pwm, etc.
    * Getting rid of ARCH_NR_GPIO,
    * Tearing out asm-generic/gpio.h into consumer/driver include files,
    * ...

    This API is only available if gpiolib is compiled in. One could however easily
    implement a set of gpiod_* functions that would wrap around the old interface if
    that was deemed necessary.

    Comments and thoughts on potential issues are welcome, at this stage it is very
    possible that I missed a few issues that will arise in later stages of this
    project.

    Alexandre Courbot (1):
    gpiolib: introduce descriptor-based GPIO interface

    drivers/gpio/gpiolib.c | 302 ++++++++++++++++++++++--------------------
    include/asm-generic/gpio.h | 74 ++++++++---
    include/linux/gpio/consumer.h | 45 +++++++
    3 files changed, 261 insertions(+), 160 deletions(-)
    create mode 100644 include/linux/gpio/consumer.h

    --
    1.8.0.1



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