diff options
Diffstat (limited to 'Documentation/driver-api/gpio')
| -rw-r--r-- | Documentation/driver-api/gpio/driver.rst | 5 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/drivers-on-gpio.rst | 8 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/driver-api/gpio/using-gpio.rst | 50 |
4 files changed, 55 insertions, 9 deletions
diff --git a/Documentation/driver-api/gpio/driver.rst b/Documentation/driver-api/gpio/driver.rst index 2ff743105927..871922529332 100644 --- a/Documentation/driver-api/gpio/driver.rst +++ b/Documentation/driver-api/gpio/driver.rst @@ -507,11 +507,6 @@ available but we try to move away from this: cascaded irq has to be handled by a threaded interrupt handler. Apart from that it works exactly like the chained irqchip. -- DEPRECATED: gpiochip_set_chained_irqchip(): sets up a chained cascaded irq - handler for a gpio_chip from a parent IRQ and passes the struct gpio_chip* - as handler data. Notice that we pass is as the handler data, since the - irqchip data is likely used by the parent irqchip. - - gpiochip_set_nested_irqchip(): sets up a nested cascaded irq handler for a gpio_chip from a parent IRQ. As the parent IRQ has usually been explicitly requested by the driver, this does very little more than diff --git a/Documentation/driver-api/gpio/drivers-on-gpio.rst b/Documentation/driver-api/gpio/drivers-on-gpio.rst index f3a189320e11..820b403d50f6 100644 --- a/Documentation/driver-api/gpio/drivers-on-gpio.rst +++ b/Documentation/driver-api/gpio/drivers-on-gpio.rst @@ -95,7 +95,7 @@ to emulate MCTRL (modem control) signals CTS/RTS by using two GPIO lines. The MTD NOR flash has add-ons for extra GPIO lines too, though the address bus is usually connected directly to the flash. -Use those instead of talking directly to the GPIOs using sysfs; they integrate -with kernel frameworks better than your userspace code could. Needless to say, -just using the appropriate kernel drivers will simplify and speed up your -embedded hacking in particular by providing ready-made components. +Use those instead of talking directly to the GPIOs from userspace; they +integrate with kernel frameworks better than your userspace code could. +Needless to say, just using the appropriate kernel drivers will simplify and +speed up your embedded hacking in particular by providing ready-made components. diff --git a/Documentation/driver-api/gpio/index.rst b/Documentation/driver-api/gpio/index.rst index 5b61032aa4ea..1d48fe248f05 100644 --- a/Documentation/driver-api/gpio/index.rst +++ b/Documentation/driver-api/gpio/index.rst @@ -8,6 +8,7 @@ Contents: :maxdepth: 2 intro + using-gpio driver consumer board diff --git a/Documentation/driver-api/gpio/using-gpio.rst b/Documentation/driver-api/gpio/using-gpio.rst new file mode 100644 index 000000000000..dda069444032 --- /dev/null +++ b/Documentation/driver-api/gpio/using-gpio.rst @@ -0,0 +1,50 @@ +========================= +Using GPIO Lines in Linux +========================= + +The Linux kernel exists to abstract and present hardware to users. GPIO lines +as such are normally not user facing abstractions. The most obvious, natural +and preferred way to use GPIO lines is to let kernel hardware drivers deal +with them. + +For examples of already existing generic drivers that will also be good +examples for any other kernel drivers you want to author, refer to +:doc:`drivers-on-gpio` + +For any kind of mass produced system you want to support, such as servers, +laptops, phones, tablets, routers, and any consumer or office or business goods +using appropriate kernel drivers is paramount. Submit your code for inclusion +in the upstream Linux kernel when you feel it is mature enough and you will get +help to refine it, see :doc:`../../process/submitting-patches`. + +In Linux GPIO lines also have a userspace ABI. + +The userspace ABI is intended for one-off deployments. Examples are prototypes, +factory lines, maker community projects, workshop specimen, production tools, +industrial automation, PLC-type use cases, door controllers, in short a piece +of specialized equipment that is not produced by the numbers, requiring +operators to have a deep knowledge of the equipment and knows about the +software-hardware interface to be set up. They should not have a natural fit +to any existing kernel subsystem and not be a good fit for an operating system, +because of not being reusable or abstract enough, or involving a lot of non +computer hardware related policy. + +Applications that have a good reason to use the industrial I/O (IIO) subsystem +from userspace will likely be a good fit for using GPIO lines from userspace as +well. + +Do not under any circumstances abuse the GPIO userspace ABI to cut corners in +any product development projects. If you use it for prototyping, then do not +productify the prototype: rewrite it using proper kernel drivers. Do not under +any circumstances deploy any uniform products using GPIO from userspace. + +The userspace ABI is a character device for each GPIO hardware unit (GPIO chip). +These devices will appear on the system as ``/dev/gpiochip0`` thru +``/dev/gpiochipN``. Examples of how to directly use the userspace ABI can be +found in the kernel tree ``tools/gpio`` subdirectory. + +For structured and managed applications, we recommend that you make use of the +libgpiod_ library. This provides helper abstractions, command line utlities +and arbitration for multiple simultaneous consumers on the same GPIO chip. + +.. _libgpiod: https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/ |