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As a way to allow the user-space to stop referring to GPIOs by their global numbers, introduce a parallel group of line attributes for exported GPIO that live inside the GPIO chip class device and are referred to by their HW offset within their parent chip. Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Link: https://lore.kernel.org/r/20250704-gpio-sysfs-chip-export-v4-8-9289d8758243@linaro.org Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
41 lines
1.7 KiB
Plaintext
41 lines
1.7 KiB
Plaintext
What: /sys/class/gpio/
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Date: July 2008
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KernelVersion: 2.6.27
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Contact: Linus Walleij <linusw@kernel.org>
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Description:
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As a Kconfig option, individual GPIO signals may be accessed from
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userspace. GPIOs are only made available to userspace by an explicit
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"export" operation. If a given GPIO is not claimed for use by
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kernel code, it may be exported by userspace (and unexported later).
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Kernel code may export it for complete or partial access.
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GPIOs are identified as they are inside the kernel, using integers in
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the range 0..INT_MAX. See Documentation/admin-guide/gpio for more information.
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::
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/sys/class/gpio
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/export ... asks the kernel to export a GPIO to userspace
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/unexport ... to return a GPIO to the kernel
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/gpioN ... for each exported GPIO #N OR
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/value ... always readable, writes fail for input GPIOs
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/direction ... r/w as: in, out (default low); write: high, low
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/edge ... r/w as: none, falling, rising, both
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/active_low ... r/w as: 0, 1
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/gpiochipN ... for each gpiochip; #N is its first GPIO
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/base ... (r/o) same as N
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/label ... (r/o) descriptive chip name
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/ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
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/gpio<OFFSET>
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/value ... always readable, writes fail for input GPIOs
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/direction ... r/w as: in, out (default low); write: high, low
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/chipX ... for each gpiochip; #X is the gpio device ID
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/export ... asks the kernel to export a GPIO at HW offset X to userspace
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/unexport ... to return a GPIO at HW offset X to the kernel
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/label ... (r/o) descriptive chip name
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/ngpio ... (r/o) number of GPIOs exposed by the chip
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This ABI is obsoleted by Documentation/ABI/testing/gpio-cdev and will be
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removed after 2020.
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