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    SubjectRe: [RFC PATCH v2 09/12] gpiolib: Identify GPIO descriptor arrays with direct mapping
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    On Tuesday, August 7, 2018 7:14:20 PM CEST Boris Brezillon wrote:
    > On Tue, 7 Aug 2018 00:29:15 +0200
    > Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:
    >
    > > Certain GPIO array lookup results may map directly to GPIO pins of a
    > > single GPIO chip in hardware order. If that condition is recognized
    > > and handled efficiently, significant performance gain of get/set array
    > > functions may be possible.
    > >
    > > While processing a request for an array of GPIO descriptors, verify if
    > > the descriptors just collected represent consecutive pins of a single
    > > GPIO chip. Pass that information with the array to the caller so it
    > > can benefit from enhanced performance as soon as bitmap based get/set
    > > array functions which can make efficient use of that are available.
    > >
    > > Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
    > > ---
    > > Documentation/driver-api/gpio/consumer.rst | 4 +++-
    > > drivers/gpio/gpiolib.c | 14 ++++++++++++++
    > > include/linux/gpio/consumer.h | 1 +
    > > 3 files changed, 18 insertions(+), 1 deletion(-)
    > >
    > > diff --git a/Documentation/driver-api/gpio/consumer.rst b/Documentation/driver-api/gpio/consumer.rst
    > > index aa03f389d41d..38a990b5f3b6 100644
    > > --- a/Documentation/driver-api/gpio/consumer.rst
    > > +++ b/Documentation/driver-api/gpio/consumer.rst
    > > @@ -109,11 +109,13 @@ For a function using multiple GPIOs all of those can be obtained with one call::
    > > enum gpiod_flags flags)
    > >
    > > This function returns a struct gpio_descs which contains an array of
    > > -descriptors::
    > > +descriptors. It may also contain a valid descriptor of a single GPIO chip in
    > > +case the array strictly matches pin hardware layout of the chip::
    > >
    > > struct gpio_descs {
    > > unsigned int ndescs;
    > > struct gpio_desc *desc[];
    > > + struct gpio_chip *chip;
    >
    > chip is placed at the beginning of the struct in the real code, which
    > is expected since putting it at the end won't work because of the
    > desc[] declaration.

    Yes, I've already noticed that and will fix on next iteration, thanks.

    Janusz


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