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Write a few words on how GPIO drivers supplying an irqchip should
be written.
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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Some devices drivers make use of optional GPIO parameters. For such
drivers, it is important to discriminate between the case where no
GPIO mapping has been defined for the function they are requesting, and
the case where a mapping exists but an error occured while resolving it
or when acquiring the GPIO.
This patch changes the family of gpiod_get() functions such that they
will return -ENOENT if and only if no GPIO mapping is defined for the
requested function. Other error codes are used when an actual error
occured during the GPIO resolution.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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Change the format of the platform GPIO lookup tables to make them less
confusing and improve lookup efficiency.
The previous format was a single linked-list that required to compare
the device name and function ID of every single GPIO defined for each
lookup. Switch that to a list of per-device tables, so that the lookup
can be done in two steps, omitting the GPIOs that are not relevant for a
particular device.
The matching rules are now defined as follows:
- The device name must match *exactly*, and can be NULL for GPIOs not
assigned to a particular device,
- If the function ID in the lookup table is NULL, the con_id argument of
gpiod_get() will not be used for lookup. However, if it is defined, it
must match exactly.
- The index must always match.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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Give a short overview of the various GPIO documentation files.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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gpiolib now exports a new descriptor-based interface which deprecates
the older integer-based one. This patch documents this new interface and
also takes the opportunity to brush-up the GPIO documentation a little
bit.
The new descriptor-based interface follows the same consumer/driver
model as many other kernel subsystems (e.g. clock, regulator), so its
documentation has similarly been splitted into different files.
The content of the former documentation has been reused whenever it
made sense; however, some of its content did not apply to the new
interface anymore and have this been removed. Likewise, new sections
like the mapping of GPIOs to devices have been written from scratch.
The deprecated legacy-based documentation is still available, untouched,
under Documentation/gpio/gpio-legacy.txt.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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