Documentation: gpio: Move legacy documentation to driver-api
Move gpio/gpio-legacy.txt to driver-api/gpio/legacy.rst and make sure it builds cleanly as ReST. Also move the legacy API reference from index.rst to legacy.rst. Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>hifive-unleashed-5.1
Jonathan Neuschäfer
Linus Walleij
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778ea833c5
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7ee2c13080
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@ -9,6 +9,7 @@ Contents:
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intro
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driver
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legacy
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Core
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====
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@ -19,15 +20,6 @@ Core
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.. kernel-doc:: drivers/gpio/gpiolib.c
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:export:
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Legacy API
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==========
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The functions listed in this section are deprecated. The GPIO descriptor based
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API described above should be used in new code.
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.. kernel-doc:: drivers/gpio/gpiolib-legacy.c
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:export:
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ACPI support
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============
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@ -1,4 +1,6 @@
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GPIO Interfaces
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======================
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Legacy GPIO Interfaces
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======================
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This provides an overview of GPIO access conventions on Linux.
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@ -129,7 +131,7 @@ The first thing a system should do with a GPIO is allocate it, using
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the gpio_request() call; see later.
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One of the next things to do with a GPIO, often in board setup code when
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setting up a platform_device using the GPIO, is mark its direction:
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setting up a platform_device using the GPIO, is mark its direction::
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/* set as input or output, returning 0 or negative errno */
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int gpio_direction_input(unsigned gpio);
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@ -164,7 +166,7 @@ Those don't need to sleep, and can safely be done from inside hard
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(nonthreaded) IRQ handlers and similar contexts.
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Use the following calls to access such GPIOs,
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for which gpio_cansleep() will always return false (see below):
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for which gpio_cansleep() will always return false (see below)::
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/* GPIO INPUT: return zero or nonzero */
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int gpio_get_value(unsigned gpio);
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@ -201,11 +203,11 @@ This requires sleeping, which can't be done from inside IRQ handlers.
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Platforms that support this type of GPIO distinguish them from other GPIOs
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by returning nonzero from this call (which requires a valid GPIO number,
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which should have been previously allocated with gpio_request):
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which should have been previously allocated with gpio_request)::
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int gpio_cansleep(unsigned gpio);
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To access such GPIOs, a different set of accessors is defined:
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To access such GPIOs, a different set of accessors is defined::
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/* GPIO INPUT: return zero or nonzero, might sleep */
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int gpio_get_value_cansleep(unsigned gpio);
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@ -222,27 +224,27 @@ Other than the fact that these accessors might sleep, and will work
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on GPIOs that can't be accessed from hardIRQ handlers, these calls act
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the same as the spinlock-safe calls.
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** IN ADDITION ** calls to setup and configure such GPIOs must be made
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**IN ADDITION** calls to setup and configure such GPIOs must be made
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from contexts which may sleep, since they may need to access the GPIO
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controller chip too: (These setup calls are usually made from board
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setup or driver probe/teardown code, so this is an easy constraint.)
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controller chip too (These setup calls are usually made from board
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setup or driver probe/teardown code, so this is an easy constraint.)::
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gpio_direction_input()
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gpio_direction_output()
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gpio_request()
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gpio_direction_input()
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gpio_direction_output()
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gpio_request()
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## gpio_request_one()
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## gpio_request_array()
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## gpio_free_array()
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## gpio_request_one()
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## gpio_request_array()
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## gpio_free_array()
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gpio_free()
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gpio_set_debounce()
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gpio_free()
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gpio_set_debounce()
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Claiming and Releasing GPIOs
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----------------------------
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To help catch system configuration errors, two calls are defined.
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To help catch system configuration errors, two calls are defined::
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/* request GPIO, returning 0 or negative errno.
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* non-null labels may be useful for diagnostics.
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@ -296,7 +298,7 @@ Also note that it's your responsibility to have stopped using a GPIO
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before you free it.
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Considering in most cases GPIOs are actually configured right after they
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are claimed, three additional calls are defined:
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are claimed, three additional calls are defined::
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/* request a single GPIO, with initial configuration specified by
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* 'flags', identical to gpio_request() wrt other arguments and
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@ -347,7 +349,7 @@ to make the pin LOW. The pin is make to HIGH by driving value 1 in output mode.
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In the future, these flags can be extended to support more properties.
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Further more, to ease the claim/release of multiple GPIOs, 'struct gpio' is
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introduced to encapsulate all three fields as:
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introduced to encapsulate all three fields as::
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struct gpio {
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unsigned gpio;
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@ -355,7 +357,7 @@ introduced to encapsulate all three fields as:
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const char *label;
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};
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A typical example of usage:
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A typical example of usage::
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static struct gpio leds_gpios[] = {
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{ 32, GPIOF_OUT_INIT_HIGH, "Power LED" }, /* default to ON */
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@ -380,7 +382,7 @@ GPIOs mapped to IRQs
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--------------------
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GPIO numbers are unsigned integers; so are IRQ numbers. These make up
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two logically distinct namespaces (GPIO 0 need not use IRQ 0). You can
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map between them using calls like:
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map between them using calls like::
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/* map GPIO numbers to IRQ numbers */
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int gpio_to_irq(unsigned gpio);
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@ -446,12 +448,12 @@ A GPIO controller on a SOC might be tightly coupled with the pinctrl
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subsystem, in the sense that the pins can be used by other functions
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together with an optional gpio feature. We have already covered the
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case where e.g. a GPIO controller need to reserve a pin or set the
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direction of a pin by calling any of:
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direction of a pin by calling any of::
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pinctrl_gpio_request()
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pinctrl_gpio_free()
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pinctrl_gpio_direction_input()
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pinctrl_gpio_direction_output()
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pinctrl_gpio_request()
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pinctrl_gpio_free()
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pinctrl_gpio_direction_input()
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pinctrl_gpio_direction_output()
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But how does the pin control subsystem cross-correlate the GPIO
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numbers (which are a global business) to a certain pin on a certain
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@ -565,7 +567,7 @@ If neither of these options are selected, the platform does not support
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GPIOs through GPIO-lib and the code cannot be enabled by the user.
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Trivial implementations of those functions can directly use framework
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code, which always dispatches through the gpio_chip:
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code, which always dispatches through the gpio_chip::
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#define gpio_get_value __gpio_get_value
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#define gpio_set_value __gpio_set_value
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@ -731,7 +733,7 @@ the correct GPIO number to use for a given signal.
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Exporting from Kernel code
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--------------------------
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Kernel code can explicitly manage exports of GPIOs which have already been
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requested using gpio_request():
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requested using gpio_request()::
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/* export the GPIO to userspace */
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int gpio_export(unsigned gpio, bool direction_may_change);
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@ -756,3 +758,13 @@ After the GPIO has been exported, gpio_export_link() allows creating
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symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can
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use this to provide the interface under their own device in sysfs with
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a descriptive name.
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API Reference
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=============
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The functions listed in this section are deprecated. The GPIO descriptor based
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API should be used in new code.
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.. kernel-doc:: drivers/gpio/gpiolib-legacy.c
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:export:
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@ -9,5 +9,3 @@ board.txt
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- How to assign GPIOs to a consumer device and a function
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sysfs.txt
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- Information about the GPIO sysfs interface
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gpio-legacy.txt
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- Historical documentation of the deprecated GPIO integer interface
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