diff options
Diffstat (limited to 'Documentation/gpio')
| -rw-r--r-- | Documentation/gpio/consumer.txt | 45 | ||||
| -rw-r--r-- | Documentation/gpio/driver.txt | 10 |
2 files changed, 51 insertions, 4 deletions
diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt index 6ce544191ca6..d85fbae451ea 100644 --- a/Documentation/gpio/consumer.txt +++ b/Documentation/gpio/consumer.txt @@ -199,6 +199,33 @@ The active-low state of a GPIO can also be queried using the following call: Note that these functions should only be used with great moderation ; a driver should not have to care about the physical line level. + +Set multiple GPIO outputs with a single function call +----------------------------------------------------- +The following functions set the output values of an array of GPIOs: + + void gpiod_set_array(unsigned int array_size, + struct gpio_desc **desc_array, + int *value_array) + void gpiod_set_raw_array(unsigned int array_size, + struct gpio_desc **desc_array, + int *value_array) + void gpiod_set_array_cansleep(unsigned int array_size, + struct gpio_desc **desc_array, + int *value_array) + void gpiod_set_raw_array_cansleep(unsigned int array_size, + struct gpio_desc **desc_array, + int *value_array) + +The array can be an arbitrary set of GPIOs. The functions will try to set +GPIOs belonging to the same bank or chip simultaneously if supported by the +corresponding chip driver. In that case a significantly improved performance +can be expected. If simultaneous setting is not possible the GPIOs will be set +sequentially. +Note that for optimal performance GPIOs belonging to the same chip should be +contiguous within the array of descriptors. + + GPIOs mapped to IRQs -------------------- GPIO lines can quite often be used as IRQs. You can get the IRQ number @@ -219,6 +246,24 @@ part of the IRQ interface, e.g. IRQF_TRIGGER_FALLING, as are system wakeup capabilities. +GPIOs and ACPI +============== + +On ACPI systems, GPIOs are described by GpioIo()/GpioInt() resources listed by +the _CRS configuration objects of devices. Those resources do not provide +connection IDs (names) for GPIOs, so it is necessary to use an additional +mechanism for this purpose. + +Systems compliant with ACPI 5.1 or newer may provide a _DSD configuration object +which, among other things, may be used to provide connection IDs for specific +GPIOs described by the GpioIo()/GpioInt() resources in _CRS. If that is the +case, it will be handled by the GPIO subsystem automatically. However, if the +_DSD is not present, the mappings between GpioIo()/GpioInt() resources and GPIO +connection IDs need to be provided by device drivers. + +For details refer to Documentation/acpi/gpio-properties.txt + + Interacting With the Legacy GPIO Subsystem ========================================== Many kernel subsystems still handle GPIOs using the legacy integer-based diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt index 18790c237977..90d0f6aba7a6 100644 --- a/Documentation/gpio/driver.txt +++ b/Documentation/gpio/driver.txt @@ -124,7 +124,8 @@ symbol: * gpiochip_set_chained_irqchip(): sets up a chained irq handler for a gpio_chip from a parent IRQ and passes the struct gpio_chip* as handler data. (Notice handler data, since the irqchip data is likely used by the - parent irqchip!) This is for the chained type of chip. + parent irqchip!) This is for the chained type of chip. This is also used + to set up a nested irqchip if NULL is passed as handler. To use the helpers please keep the following in mind: @@ -157,12 +158,12 @@ Locking IRQ usage Input GPIOs can be used as IRQ signals. When this happens, a driver is requested to mark the GPIO as being used as an IRQ: - int gpio_lock_as_irq(struct gpio_chip *chip, unsigned int offset) + int gpiochip_lock_as_irq(struct gpio_chip *chip, unsigned int offset) This will prevent the use of non-irq related GPIO APIs until the GPIO IRQ lock is released: - void gpio_unlock_as_irq(struct gpio_chip *chip, unsigned int offset) + void gpiochip_unlock_as_irq(struct gpio_chip *chip, unsigned int offset) When implementing an irqchip inside a GPIO driver, these two functions should typically be called in the .startup() and .shutdown() callbacks from the @@ -178,7 +179,8 @@ does not help since it pins the module to the kernel forever (it calls try_module_get()). A GPIO driver can use the following functions instead to request and free descriptors without being pinned to the kernel forever. - int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label) + struct gpio_desc *gpiochip_request_own_desc(struct gpio_desc *desc, + const char *label) void gpiochip_free_own_desc(struct gpio_desc *desc) |