diff options
Diffstat (limited to 'Documentation/driver-api/gpio')
| -rw-r--r-- | Documentation/driver-api/gpio/board.rst | 24 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/consumer.rst | 64 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/driver.rst | 23 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/index.rst | 2 |
4 files changed, 89 insertions, 24 deletions
diff --git a/Documentation/driver-api/gpio/board.rst b/Documentation/driver-api/gpio/board.rst index 2c112553df84..a0f294e2e250 100644 --- a/Documentation/driver-api/gpio/board.rst +++ b/Documentation/driver-api/gpio/board.rst @@ -193,3 +193,27 @@ And the table can be added to the board code as follows:: The line will be hogged as soon as the gpiochip is created or - in case the chip was created earlier - when the hog table is registered. + +Arrays of pins +-------------- +In addition to requesting pins belonging to a function one by one, a device may +also request an array of pins assigned to the function. The way those pins are +mapped to the device determines if the array qualifies for fast bitmap +processing. If yes, a bitmap is passed over get/set array functions directly +between a caller and a respective .get/set_multiple() callback of a GPIO chip. + +In order to qualify for fast bitmap processing, the array must meet the +following requirements: +- pin hardware number of array member 0 must also be 0, +- pin hardware numbers of consecutive array members which belong to the same + chip as member 0 does must also match their array indexes. + +Otherwise fast bitmap processing path is not used in order to avoid consecutive +pins which belong to the same chip but are not in hardware order being processed +separately. + +If the array applies for fast bitmap processing path, pins which belong to +different chips than member 0 does, as well as those with indexes different from +their hardware pin numbers, are excluded from the fast path, both input and +output. Moreover, open drain and open source pins are excluded from fast bitmap +output processing. diff --git a/Documentation/driver-api/gpio/consumer.rst b/Documentation/driver-api/gpio/consumer.rst index aa03f389d41d..5e4d8aa68913 100644 --- a/Documentation/driver-api/gpio/consumer.rst +++ b/Documentation/driver-api/gpio/consumer.rst @@ -109,9 +109,11 @@ 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 also contains a pointer to a gpiolib private structure which, +if passed back to get/set array functions, may speed up I/O proocessing:: struct gpio_descs { + struct gpio_array *info; unsigned int ndescs; struct gpio_desc *desc[]; } @@ -323,29 +325,37 @@ The following functions get or set the values of an array of GPIOs:: int gpiod_get_array_value(unsigned int array_size, struct gpio_desc **desc_array, - int *value_array); + struct gpio_array *array_info, + unsigned long *value_bitmap); int gpiod_get_raw_array_value(unsigned int array_size, struct gpio_desc **desc_array, - int *value_array); + struct gpio_array *array_info, + unsigned long *value_bitmap); int gpiod_get_array_value_cansleep(unsigned int array_size, struct gpio_desc **desc_array, - int *value_array); + struct gpio_array *array_info, + unsigned long *value_bitmap); int gpiod_get_raw_array_value_cansleep(unsigned int array_size, struct gpio_desc **desc_array, - int *value_array); - - void gpiod_set_array_value(unsigned int array_size, - struct gpio_desc **desc_array, - int *value_array) - void gpiod_set_raw_array_value(unsigned int array_size, - struct gpio_desc **desc_array, - int *value_array) - void gpiod_set_array_value_cansleep(unsigned int array_size, - struct gpio_desc **desc_array, - int *value_array) - void gpiod_set_raw_array_value_cansleep(unsigned int array_size, - struct gpio_desc **desc_array, - int *value_array) + struct gpio_array *array_info, + unsigned long *value_bitmap); + + int gpiod_set_array_value(unsigned int array_size, + struct gpio_desc **desc_array, + struct gpio_array *array_info, + unsigned long *value_bitmap) + int gpiod_set_raw_array_value(unsigned int array_size, + struct gpio_desc **desc_array, + struct gpio_array *array_info, + unsigned long *value_bitmap) + int gpiod_set_array_value_cansleep(unsigned int array_size, + struct gpio_desc **desc_array, + struct gpio_array *array_info, + unsigned long *value_bitmap) + int gpiod_set_raw_array_value_cansleep(unsigned int array_size, + struct gpio_desc **desc_array, + struct gpio_array *array_info, + unsigned long *value_bitmap) The array can be an arbitrary set of GPIOs. The functions will try to access GPIOs belonging to the same bank or chip simultaneously if supported by the @@ -356,8 +366,9 @@ accessed sequentially. The functions take three arguments: * array_size - the number of array elements * desc_array - an array of GPIO descriptors - * value_array - an array to store the GPIOs' values (get) or - an array of values to assign to the GPIOs (set) + * array_info - optional information obtained from gpiod_array_get() + * value_bitmap - a bitmap to store the GPIOs' values (get) or + a bitmap of values to assign to the GPIOs (set) The descriptor array can be obtained using the gpiod_get_array() function or one of its variants. If the group of descriptors returned by that function @@ -366,16 +377,25 @@ the struct gpio_descs returned by gpiod_get_array():: struct gpio_descs *my_gpio_descs = gpiod_get_array(...); gpiod_set_array_value(my_gpio_descs->ndescs, my_gpio_descs->desc, - my_gpio_values); + my_gpio_descs->info, my_gpio_value_bitmap); It is also possible to access a completely arbitrary array of descriptors. The descriptors may be obtained using any combination of gpiod_get() and gpiod_get_array(). Afterwards the array of descriptors has to be setup -manually before it can be passed to one of the above functions. +manually before it can be passed to one of the above functions. In that case, +array_info should be set to NULL. Note that for optimal performance GPIOs belonging to the same chip should be contiguous within the array of descriptors. +Still better performance may be achieved if array indexes of the descriptors +match hardware pin numbers of a single chip. If an array passed to a get/set +array function matches the one obtained from gpiod_get_array() and array_info +associated with the array is also passed, the function may take a fast bitmap +processing path, passing the value_bitmap argument directly to the respective +.get/set_multiple() callback of the chip. That allows for utilization of GPIO +banks as data I/O ports without much loss of performance. + The return value of gpiod_get_array_value() and its variants is 0 on success or negative on error. Note the difference to gpiod_get_value(), which returns 0 or 1 on success to convey the GPIO value. With the array functions, the GPIO diff --git a/Documentation/driver-api/gpio/driver.rst b/Documentation/driver-api/gpio/driver.rst index cbe0242842d1..a6c14ff0c54f 100644 --- a/Documentation/driver-api/gpio/driver.rst +++ b/Documentation/driver-api/gpio/driver.rst @@ -374,7 +374,28 @@ When implementing an irqchip inside a GPIO driver, these two functions should typically be called in the .startup() and .shutdown() callbacks from the irqchip. -When using the gpiolib irqchip helpers, these callback are automatically +When using the gpiolib irqchip helpers, these callbacks are automatically +assigned. + + +Disabling and enabling IRQs +--------------------------- +When a GPIO is used as an IRQ signal, then gpiolib also needs to know if +the IRQ is enabled or disabled. In order to inform gpiolib about this, +a driver should call:: + + void gpiochip_disable_irq(struct gpio_chip *chip, unsigned int offset) + +This allows drivers to drive the GPIO as an output while the IRQ is +disabled. When the IRQ is enabled again, a driver should call:: + + void gpiochip_enable_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 .irq_disable() and .irq_enable() callbacks from the +irqchip. + +When using the gpiolib irqchip helpers, these callbacks are automatically assigned. Real-Time compliance for GPIO IRQ chips diff --git a/Documentation/driver-api/gpio/index.rst b/Documentation/driver-api/gpio/index.rst index 6a374ded1287..c5b8467f9104 100644 --- a/Documentation/driver-api/gpio/index.rst +++ b/Documentation/driver-api/gpio/index.rst @@ -38,7 +38,7 @@ Device tree support Device-managed API ================== -.. kernel-doc:: drivers/gpio/devres.c +.. kernel-doc:: drivers/gpio/gpiolib-devres.c :export: sysfs helpers |