5ca84d416e
The documentation does not make sufficiently clear that the uAPI deals with logical line values, nor does it describe the influence of the active low flag on the mapping between physical and logical line values. Clarify the relationship between physical and logical line values and the effect of the active low flag for ioctls passing line values. Suggested-by: David C. Rankin <drankinatty@gmail.com> Signed-off-by: Kent Gibson <warthog618@gmail.com> Link: https://lore.kernel.org/r/20240610092157.9147-2-warthog618@gmail.com Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
56 lines
1.5 KiB
ReStructuredText
56 lines
1.5 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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.. _GPIO_HANDLE_SET_LINE_VALUES_IOCTL:
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*********************************
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GPIO_HANDLE_SET_LINE_VALUES_IOCTL
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*********************************
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.. warning::
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This ioctl is part of chardev_v1.rst and is obsoleted by
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gpio-v2-line-set-values-ioctl.rst.
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Name
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====
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GPIO_HANDLE_SET_LINE_VALUES_IOCTL - Set the values of all requested output lines.
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Synopsis
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========
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.. c:macro:: GPIO_HANDLE_SET_LINE_VALUES_IOCTL
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``int ioctl(int handle_fd, GPIO_HANDLE_SET_LINE_VALUES_IOCTL, struct gpiohandle_data *values)``
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Arguments
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=========
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``handle_fd``
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The file descriptor of the GPIO character device, as returned in the
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:c:type:`request.fd<gpiohandle_request>` by gpio-get-linehandle-ioctl.rst.
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``values``
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The :c:type:`line_values<gpiohandle_data>` to set.
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Description
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===========
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Set the values of all requested output lines.
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The values set are logical, indicating if the line is to be active or inactive.
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The ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` flag controls the mapping between logical
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values (active/inactive) and physical values (high/low).
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If ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` is not set then active is high and
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inactive is low. If ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` is set then active is low
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and inactive is high.
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Only the values of output lines may be set.
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Attempting to set the value of input lines is an error (**EPERM**).
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Return Value
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============
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On success 0.
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On error -1 and the ``errno`` variable is set appropriately.
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Common error codes are described in error-codes.rst.
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