diff options
Diffstat (limited to 'Documentation/driver-api')
| -rw-r--r-- | Documentation/driver-api/gpio/legacy.rst | 31 |
1 files changed, 1 insertions, 30 deletions
diff --git a/Documentation/driver-api/gpio/legacy.rst b/Documentation/driver-api/gpio/legacy.rst index 78372853c6d4..b6505914791c 100644 --- a/Documentation/driver-api/gpio/legacy.rst +++ b/Documentation/driver-api/gpio/legacy.rst @@ -165,8 +165,7 @@ Most GPIO controllers can be accessed with memory read/write instructions. Those don't need to sleep, and can safely be done from inside hard (nonthreaded) IRQ handlers and similar contexts. -Use the following calls to access such GPIOs, -for which gpio_cansleep() will always return false (see below):: +Use the following calls to access such GPIOs:: /* GPIO INPUT: return zero or nonzero */ int gpio_get_value(unsigned gpio); @@ -200,13 +199,6 @@ Some GPIO controllers must be accessed using message based busses like I2C or SPI. Commands to read or write those GPIO values require waiting to get to the head of a queue to transmit a command and get its response. This requires sleeping, which can't be done from inside IRQ handlers. - -Platforms that support this type of GPIO distinguish them from other GPIOs -by returning nonzero from this call (which requires a valid GPIO number, -which should have been previously allocated with gpio_request):: - - int gpio_cansleep(unsigned gpio); - To access such GPIOs, a different set of accessors is defined:: /* GPIO INPUT: return zero or nonzero, might sleep */ @@ -215,7 +207,6 @@ To access such GPIOs, a different set of accessors is defined:: /* GPIO OUTPUT, might sleep */ void gpio_set_value_cansleep(unsigned gpio, int value); - Accessing such GPIOs requires a context which may sleep, for example a threaded IRQ handler, and those accessors must be used instead of spinlock-safe accessors without the cansleep() name suffix. @@ -319,11 +310,6 @@ where 'flags' is currently defined to specify the following properties: * GPIOF_INIT_LOW - as output, set initial level to LOW * GPIOF_INIT_HIGH - as output, set initial level to HIGH - * GPIOF_OPEN_DRAIN - gpio pin is open drain type. - * GPIOF_OPEN_SOURCE - gpio pin is open source type. - - * GPIOF_EXPORT_DIR_FIXED - export gpio to sysfs, keep direction - * GPIOF_EXPORT_DIR_CHANGEABLE - also export, allow changing direction since GPIOF_INIT_* are only valid when configured as output, so group valid combinations as: @@ -332,20 +318,6 @@ combinations as: * GPIOF_OUT_INIT_LOW - configured as output, initial level LOW * GPIOF_OUT_INIT_HIGH - configured as output, initial level HIGH -When setting the flag as GPIOF_OPEN_DRAIN then it will assume that pins is -open drain type. Such pins will not be driven to 1 in output mode. It is -require to connect pull-up on such pins. By enabling this flag, gpio lib will -make the direction to input when it is asked to set value of 1 in output mode -to make the pin HIGH. The pin is make to LOW by driving value 0 in output mode. - -When setting the flag as GPIOF_OPEN_SOURCE then it will assume that pins is -open source type. Such pins will not be driven to 0 in output mode. It is -require to connect pull-down on such pin. By enabling this flag, gpio lib will -make the direction to input when it is asked to set value of 0 in output mode -to make the pin LOW. The pin is make to HIGH by driving value 1 in output mode. - -In the future, these flags can be extended to support more properties. - Further more, to ease the claim/release of multiple GPIOs, 'struct gpio' is introduced to encapsulate all three fields as:: @@ -556,7 +528,6 @@ code, which always dispatches through the gpio_chip:: #define gpio_get_value __gpio_get_value #define gpio_set_value __gpio_set_value - #define gpio_cansleep __gpio_cansleep Fancier implementations could instead define those as inline functions with logic optimizing access to specific SOC-based GPIOs. For example, if the |