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Diffstat (limited to 'Documentation/driver-api/gpio/using-gpio.rst')
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diff --git a/Documentation/driver-api/gpio/using-gpio.rst b/Documentation/driver-api/gpio/using-gpio.rst new file mode 100644 index 0000000000..894d88855d --- /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 +Documentation/driver-api/gpio/drivers-on-gpio.rst + +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 Documentation/process/submitting-patches.rst. + +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 utilities +and arbitration for multiple simultaneous consumers on the same GPIO chip. + +.. _libgpiod: https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/ |