€•‚      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ,/translations/zh_CN/userspace-api/gpio/sysfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/zh_TW/userspace-api/gpio/sysfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/it_IT/userspace-api/gpio/sysfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/ja_JP/userspace-api/gpio/sysfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/ko_KR/userspace-api/gpio/sysfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ,/translations/sp_SP/userspace-api/gpio/sysfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒ"GPIO Sysfs Interface for Userspace”h]”hŒ"GPIO Sysfs Interface for Userspace”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒF/var/lib/git/docbuild/linux/Documentation/userspace-api/gpio/sysfs.rst”h KubhŒwarning”“”)”}”(hXš  This API is obsoleted by the chardev.rst and the ABI documentation has
been moved to Documentation/ABI/obsolete/sysfs-gpio.

New developments should use the chardev.rst, and existing developments are
encouraged to migrate as soon as possible, as this API will be removed
in the future.

This interface will continue to be maintained for the migration period,
but new features will only be added to the new API.”h]”(hŒ	paragraph”“”)”}”(hŒ{This API is obsoleted by the chardev.rst and the ABI documentation has
been moved to Documentation/ABI/obsolete/sysfs-gpio.”h]”hŒ{This API is obsoleted by the chardev.rst and the ABI documentation has
been moved to Documentation/ABI/obsolete/sysfs-gpio.”…””}”(hh¿hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Khh¹ubh¾)”}”(hŒ New developments should use the chardev.rst, and existing developments are
encouraged to migrate as soon as possible, as this API will be removed
in the future.”h]”hŒ New developments should use the chardev.rst, and existing developments are
encouraged to migrate as soon as possible, as this API will be removed
in the future.”…””}”(hhÍhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Khh¹ubh¾)”}”(hŒ{This interface will continue to be maintained for the migration period,
but new features will only be added to the new API.”h]”hŒ{This interface will continue to be maintained for the migration period,
but new features will only be added to the new API.”…””}”(hhÛhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Khh¹ubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hh£hžhhŸh¶h Nubh¢)”}”(hhh]”(h§)”}”(hŒThe obsolete sysfs ABI”h]”hŒThe obsolete sysfs ABI”…””}”(hhòhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hhïhžhhŸh¶h Kubh¾)”}”(hXP  Platforms which use the "gpiolib" implementors framework may choose to
configure a sysfs user interface to GPIOs. This is different from the
debugfs interface, since it provides control over GPIO direction and
value instead of just showing a gpio state summary. Plus, it could be
present on production systems without debugging support.”h]”hXT  Platforms which use the â€œgpiolibâ€ implementors framework may choose to
configure a sysfs user interface to GPIOs. This is different from the
debugfs interface, since it provides control over GPIO direction and
value instead of just showing a gpio state summary. Plus, it could be
present on production systems without debugging support.”…””}”(hj   hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Khhïhžhubh¾)”}”(hXã  Given appropriate hardware documentation for the system, userspace could
know for example that GPIO #23 controls the write protect line used to
protect boot loader segments in flash memory. System upgrade procedures
may need to temporarily remove that protection, first importing a GPIO,
then changing its output state, then updating the code before re-enabling
the write protection. In normal use, GPIO #23 would never be touched,
and the kernel would have no need to know about it.”h]”hXã  Given appropriate hardware documentation for the system, userspace could
know for example that GPIO #23 controls the write protect line used to
protect boot loader segments in flash memory. System upgrade procedures
may need to temporarily remove that protection, first importing a GPIO,
then changing its output state, then updating the code before re-enabling
the write protection. In normal use, GPIO #23 would never be touched,
and the kernel would have no need to know about it.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Khhïhžhubh¾)”}”(hX  Again depending on appropriate hardware documentation, on some systems
userspace GPIO can be used to determine system configuration data that
standard kernels won't know about. And for some tasks, simple userspace
GPIO drivers could be all that the system really needs.”h]”hX  Again depending on appropriate hardware documentation, on some systems
userspace GPIO can be used to determine system configuration data that
standard kernels wonâ€™t know about. And for some tasks, simple userspace
GPIO drivers could be all that the system really needs.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KhhïhžhubhŒnote”“”)”}”(hŒÉDo NOT abuse sysfs to control hardware that has proper kernel drivers.
Please read Documentation/driver-api/gpio/drivers-on-gpio.rst
to avoid reinventing kernel wheels in userspace.

I MEAN IT. REALLY.”h]”(h¾)”}”(hŒµDo NOT abuse sysfs to control hardware that has proper kernel drivers.
Please read Documentation/driver-api/gpio/drivers-on-gpio.rst
to avoid reinventing kernel wheels in userspace.”h]”hŒµDo NOT abuse sysfs to control hardware that has proper kernel drivers.
Please read Documentation/driver-api/gpio/drivers-on-gpio.rst
to avoid reinventing kernel wheels in userspace.”…””}”(hj0  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K%hj,  ubh¾)”}”(hŒI MEAN IT. REALLY.”h]”hŒI MEAN IT. REALLY.”…””}”(hj>  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K)hj,  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j*  hhïhžhhŸh¶h Nubeh}”(h]”Œthe-obsolete-sysfs-abi”ah ]”h"]”Œthe obsolete sysfs abi”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒPaths in Sysfs”h]”hŒPaths in Sysfs”…””}”(hj]  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjZ  hžhhŸh¶h K,ubh¾)”}”(hŒ4There are three kinds of entries in /sys/class/gpio:”h]”hŒ4There are three kinds of entries in /sys/class/gpio:”…””}”(hjk  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K-hjZ  hžhubhŒblock_quote”“”)”}”(hŒŽ-    Control interfaces used to get userspace control over GPIOs;

-    GPIOs themselves; and

-    GPIO controllers ("gpio_chip" instances).
”h]”hŒbullet_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒ=Control interfaces used to get userspace control over GPIOs;
”h]”h¾)”}”(hŒ<Control interfaces used to get userspace control over GPIOs;”h]”hŒ<Control interfaces used to get userspace control over GPIOs;”…””}”(hjŠ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K/hj†  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j„  hj  ubj…  )”}”(hŒGPIOs themselves; and
”h]”h¾)”}”(hŒGPIOs themselves; and”h]”hŒGPIOs themselves; and”…””}”(hj¢  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K1hjž  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j„  hj  ubj…  )”}”(hŒ*GPIO controllers ("gpio_chip" instances).
”h]”h¾)”}”(hŒ)GPIO controllers ("gpio_chip" instances).”h]”hŒ-GPIO controllers (â€œgpio_chipâ€ instances).”…””}”(hjº  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K3hj¶  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j„  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1j  hŸh¶h K/hj{  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jy  hŸh¶h K/hjZ  hžhubh¾)”}”(hŒDThat's in addition to standard files including the "device" symlink.”h]”hŒJThatâ€™s in addition to standard files including the â€œdeviceâ€ symlink.”…””}”(hjÜ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K5hjZ  hžhubh¾)”}”(hŒ&The control interfaces are write-only:”h]”hŒ&The control interfaces are write-only:”…””}”(hjê  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K7hjZ  hžhubjz  )”}”(hXò  /sys/class/gpio/

    "export" ...
            Userspace may ask the kernel to export control of
            a GPIO to userspace by writing its number to this file.

            Example:  "echo 19 > export" will create a "gpio19" node
            for GPIO #19, if that's not requested by kernel code.

    "unexport" ...
            Reverses the effect of exporting to userspace.

            Example:  "echo 19 > unexport" will remove a "gpio19"
            node exported using the "export" file.
”h]”(h¾)”}”(hŒ/sys/class/gpio/”h]”hŒ/sys/class/gpio/”…””}”(hjü  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K9hjø  ubjz  )”}”(hX¼  "export" ...
        Userspace may ask the kernel to export control of
        a GPIO to userspace by writing its number to this file.

        Example:  "echo 19 > export" will create a "gpio19" node
        for GPIO #19, if that's not requested by kernel code.

"unexport" ...
        Reverses the effect of exporting to userspace.

        Example:  "echo 19 > unexport" will remove a "gpio19"
        node exported using the "export" file.
”h]”hŒdefinition_list”“”)”}”(hhh]”(hŒdefinition_list_item”“”)”}”(hŒç"export" ...
Userspace may ask the kernel to export control of
a GPIO to userspace by writing its number to this file.

Example:  "echo 19 > export" will create a "gpio19" node
for GPIO #19, if that's not requested by kernel code.
”h]”(hŒterm”“”)”}”(hŒ"export" ...”h]”hŒâ€œexportâ€ ...”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h K@hj  ubhŒ
definition”“”)”}”(hhh]”(h¾)”}”(hŒiUserspace may ask the kernel to export control of
a GPIO to userspace by writing its number to this file.”h]”hŒiUserspace may ask the kernel to export control of
a GPIO to userspace by writing its number to this file.”…””}”(hj.  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K<hj+  ubh¾)”}”(hŒnExample:  "echo 19 > export" will create a "gpio19" node
for GPIO #19, if that's not requested by kernel code.”h]”hŒxExample:  â€œecho 19 > exportâ€ will create a â€œgpio19â€ node
for GPIO #19, if thatâ€™s not requested by kernel code.”…””}”(hj<  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K?hj+  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j)  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h K@hj  ubj  )”}”(hŒœ"unexport" ...
Reverses the effect of exporting to userspace.

Example:  "echo 19 > unexport" will remove a "gpio19"
node exported using the "export" file.
”h]”(j  )”}”(hŒ"unexport" ...”h]”hŒâ€œunexportâ€ ...”…””}”(hjZ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h KFhjV  ubj*  )”}”(hhh]”(h¾)”}”(hŒ.Reverses the effect of exporting to userspace.”h]”hŒ.Reverses the effect of exporting to userspace.”…””}”(hjk  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KChjh  ubh¾)”}”(hŒ\Example:  "echo 19 > unexport" will remove a "gpio19"
node exported using the "export" file.”h]”hŒhExample:  â€œecho 19 > unexportâ€ will remove a â€œgpio19â€
node exported using the â€œexportâ€ file.”…””}”(hjy  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KEhjh  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j)  hjV  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h KFhj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hj
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jy  hŸh¶h K;hjø  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jy  hŸh¶h K9hjZ  hžhubh¾)”}”(hŒqGPIO signals have paths like /sys/class/gpio/gpio42/ (for GPIO #42)
and have the following read/write attributes:”h]”hŒqGPIO signals have paths like /sys/class/gpio/gpio42/ (for GPIO #42)
and have the following read/write attributes:”…””}”(hj¥  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KHhjZ  hžhubjz  )”}”(hX”  /sys/class/gpio/gpioN/

    "direction" ...
            reads as either "in" or "out". This value may
            normally be written. Writing as "out" defaults to
            initializing the value as low. To ensure glitch free
            operation, values "low" and "high" may be written to
            configure the GPIO as an output with that initial value.

            Note that this attribute *will not exist* if the kernel
            doesn't support changing the direction of a GPIO, or
            it was exported by kernel code that didn't explicitly
            allow userspace to reconfigure this GPIO's direction.

    "value" ...
            reads as either 0 (inactive) or 1 (active). If the GPIO
            is configured as an output, this value may be written;
            any nonzero value is treated as active.

            If the pin can be configured as interrupt-generating interrupt
            and if it has been configured to generate interrupts (see the
            description of "edge"), you can poll(2) on that file and
            poll(2) will return whenever the interrupt was triggered. If
            you use poll(2), set the events POLLPRI and POLLERR. If you
            use select(2), set the file descriptor in exceptfds. After
            poll(2) returns, use pread(2) to read the value at offset
            zero. Alternatively, either lseek(2) to the beginning of the
            sysfs file and read the new value or close the file and
            re-open it to read the value.

    "edge" ...
            reads as either "none", "rising", "falling", or
            "both". Write these strings to select the signal edge(s)
            that will make poll(2) on the "value" file return.

            This file exists only if the pin can be configured as an
            interrupt generating input pin.

    "active_low" ...
            reads as either 0 (false) or 1 (true). Write
            any nonzero value to invert the value attribute both
            for reading and writing. Existing and subsequent
            poll(2) support configuration via the edge attribute
            for "rising" and "falling" edges will follow this
            setting.
”h]”(h¾)”}”(hŒ/sys/class/gpio/gpioN/”h]”hŒ/sys/class/gpio/gpioN/”…””}”(hj·  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KKhj³  ubjz  )”}”(hXè  "direction" ...
        reads as either "in" or "out". This value may
        normally be written. Writing as "out" defaults to
        initializing the value as low. To ensure glitch free
        operation, values "low" and "high" may be written to
        configure the GPIO as an output with that initial value.

        Note that this attribute *will not exist* if the kernel
        doesn't support changing the direction of a GPIO, or
        it was exported by kernel code that didn't explicitly
        allow userspace to reconfigure this GPIO's direction.

"value" ...
        reads as either 0 (inactive) or 1 (active). If the GPIO
        is configured as an output, this value may be written;
        any nonzero value is treated as active.

        If the pin can be configured as interrupt-generating interrupt
        and if it has been configured to generate interrupts (see the
        description of "edge"), you can poll(2) on that file and
        poll(2) will return whenever the interrupt was triggered. If
        you use poll(2), set the events POLLPRI and POLLERR. If you
        use select(2), set the file descriptor in exceptfds. After
        poll(2) returns, use pread(2) to read the value at offset
        zero. Alternatively, either lseek(2) to the beginning of the
        sysfs file and read the new value or close the file and
        re-open it to read the value.

"edge" ...
        reads as either "none", "rising", "falling", or
        "both". Write these strings to select the signal edge(s)
        that will make poll(2) on the "value" file return.

        This file exists only if the pin can be configured as an
        interrupt generating input pin.

"active_low" ...
        reads as either 0 (false) or 1 (true). Write
        any nonzero value to invert the value attribute both
        for reading and writing. Existing and subsequent
        poll(2) support configuration via the edge attribute
        for "rising" and "falling" edges will follow this
        setting.
”h]”j  )”}”(hhh]”(j  )”}”(hXí  "direction" ...
reads as either "in" or "out". This value may
normally be written. Writing as "out" defaults to
initializing the value as low. To ensure glitch free
operation, values "low" and "high" may be written to
configure the GPIO as an output with that initial value.

Note that this attribute *will not exist* if the kernel
doesn't support changing the direction of a GPIO, or
it was exported by kernel code that didn't explicitly
allow userspace to reconfigure this GPIO's direction.
”h]”(j  )”}”(hŒ"direction" ...”h]”hŒâ€œdirectionâ€ ...”…””}”(hjÐ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h KWhjÌ  ubj*  )”}”(hhh]”(h¾)”}”(hX  reads as either "in" or "out". This value may
normally be written. Writing as "out" defaults to
initializing the value as low. To ensure glitch free
operation, values "low" and "high" may be written to
configure the GPIO as an output with that initial value.”h]”hX  reads as either â€œinâ€ or â€œoutâ€. This value may
normally be written. Writing as â€œoutâ€ defaults to
initializing the value as low. To ensure glitch free
operation, values â€œlowâ€ and â€œhighâ€ may be written to
configure the GPIO as an output with that initial value.”…””}”(hjá  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KNhjÞ  ubh¾)”}”(hŒØNote that this attribute *will not exist* if the kernel
doesn't support changing the direction of a GPIO, or
it was exported by kernel code that didn't explicitly
allow userspace to reconfigure this GPIO's direction.”h]”(hŒNote that this attribute ”…””}”(hjï  hžhhŸNh NubhŒemphasis”“”)”}”(hŒ*will not exist*”h]”hŒwill not exist”…””}”(hjù  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j÷  hjï  ubhŒµ if the kernel
doesnâ€™t support changing the direction of a GPIO, or
it was exported by kernel code that didnâ€™t explicitly
allow userspace to reconfigure this GPIOâ€™s direction.”…””}”(hjï  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KThjÞ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j)  hjÌ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h KWhjÉ  ubj  )”}”(hXÛ  "value" ...
reads as either 0 (inactive) or 1 (active). If the GPIO
is configured as an output, this value may be written;
any nonzero value is treated as active.

If the pin can be configured as interrupt-generating interrupt
and if it has been configured to generate interrupts (see the
description of "edge"), you can poll(2) on that file and
poll(2) will return whenever the interrupt was triggered. If
you use poll(2), set the events POLLPRI and POLLERR. If you
use select(2), set the file descriptor in exceptfds. After
poll(2) returns, use pread(2) to read the value at offset
zero. Alternatively, either lseek(2) to the beginning of the
sysfs file and read the new value or close the file and
re-open it to read the value.
”h]”(j  )”}”(hŒ"value" ...”h]”hŒâ€œvalueâ€ ...”…””}”(hj!  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h Kghj  ubj*  )”}”(hhh]”(h¾)”}”(hŒ–reads as either 0 (inactive) or 1 (active). If the GPIO
is configured as an output, this value may be written;
any nonzero value is treated as active.”h]”hŒ–reads as either 0 (inactive) or 1 (active). If the GPIO
is configured as an output, this value may be written;
any nonzero value is treated as active.”…””}”(hj2  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KZhj/  ubh¾)”}”(hX6  If the pin can be configured as interrupt-generating interrupt
and if it has been configured to generate interrupts (see the
description of "edge"), you can poll(2) on that file and
poll(2) will return whenever the interrupt was triggered. If
you use poll(2), set the events POLLPRI and POLLERR. If you
use select(2), set the file descriptor in exceptfds. After
poll(2) returns, use pread(2) to read the value at offset
zero. Alternatively, either lseek(2) to the beginning of the
sysfs file and read the new value or close the file and
re-open it to read the value.”h]”hX:  If the pin can be configured as interrupt-generating interrupt
and if it has been configured to generate interrupts (see the
description of â€œedgeâ€), you can poll(2) on that file and
poll(2) will return whenever the interrupt was triggered. If
you use poll(2), set the events POLLPRI and POLLERR. If you
use select(2), set the file descriptor in exceptfds. After
poll(2) returns, use pread(2) to read the value at offset
zero. Alternatively, either lseek(2) to the beginning of the
sysfs file and read the new value or close the file and
re-open it to read the value.”…””}”(hj@  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K^hj/  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j)  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h KghjÉ  ubj  )”}”(hX  "edge" ...
reads as either "none", "rising", "falling", or
"both". Write these strings to select the signal edge(s)
that will make poll(2) on the "value" file return.

This file exists only if the pin can be configured as an
interrupt generating input pin.
”h]”(j  )”}”(hŒ
"edge" ...”h]”hŒâ€œedgeâ€ ...”…””}”(hj^  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h KohjZ  ubj*  )”}”(hhh]”(h¾)”}”(hŒ›reads as either "none", "rising", "falling", or
"both". Write these strings to select the signal edge(s)
that will make poll(2) on the "value" file return.”h]”hŒ¯reads as either â€œnoneâ€, â€œrisingâ€, â€œfallingâ€, or
â€œbothâ€. Write these strings to select the signal edge(s)
that will make poll(2) on the â€œvalueâ€ file return.”…””}”(hjo  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Kjhjl  ubh¾)”}”(hŒXThis file exists only if the pin can be configured as an
interrupt generating input pin.”h]”hŒXThis file exists only if the pin can be configured as an
interrupt generating input pin.”…””}”(hj}  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Knhjl  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j)  hjZ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h KohjÉ  ubj  )”}”(hX  "active_low" ...
reads as either 0 (false) or 1 (true). Write
any nonzero value to invert the value attribute both
for reading and writing. Existing and subsequent
poll(2) support configuration via the edge attribute
for "rising" and "falling" edges will follow this
setting.
”h]”(j  )”}”(hŒ"active_low" ...”h]”hŒâ€œactive_lowâ€ ...”…””}”(hj›  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h Kwhj—  ubj*  )”}”(hhh]”h¾)”}”(hX  reads as either 0 (false) or 1 (true). Write
any nonzero value to invert the value attribute both
for reading and writing. Existing and subsequent
poll(2) support configuration via the edge attribute
for "rising" and "falling" edges will follow this
setting.”h]”hX
  reads as either 0 (false) or 1 (true). Write
any nonzero value to invert the value attribute both
for reading and writing. Existing and subsequent
poll(2) support configuration via the edge attribute
for â€œrisingâ€ and â€œfallingâ€ edges will follow this
setting.”…””}”(hj¬  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Krhj©  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j)  hj—  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h KwhjÉ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hjÅ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jy  hŸh¶h KMhj³  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jy  hŸh¶h KKhjZ  hžhubh¾)”}”(hŒ¡GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
controller implementing GPIOs starting at #42) and have the following
read-only attributes:”h]”hŒ¡GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
controller implementing GPIOs starting at #42) and have the following
read-only attributes:”…””}”(hjØ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KyhjZ  hžhubjz  )”}”(hŒþ/sys/class/gpio/gpiochipN/

    "base" ...
            same as N, the first GPIO managed by this chip

    "label" ...
            provided for diagnostics (not always unique)

    "ngpio" ...
            how many GPIOs this manages (N to N + ngpio - 1)
”h]”(h¾)”}”(hŒ/sys/class/gpio/gpiochipN/”h]”hŒ/sys/class/gpio/gpiochipN/”…””}”(hjê  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K}hjæ  ubjz  )”}”(hŒÊ"base" ...
        same as N, the first GPIO managed by this chip

"label" ...
        provided for diagnostics (not always unique)

"ngpio" ...
        how many GPIOs this manages (N to N + ngpio - 1)
”h]”j  )”}”(hhh]”(j  )”}”(hŒ:"base" ...
same as N, the first GPIO managed by this chip
”h]”(j  )”}”(hŒ
"base" ...”h]”hŒâ€œbaseâ€ ...”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h K€hjÿ  ubj*  )”}”(hhh]”h¾)”}”(hŒ.same as N, the first GPIO managed by this chip”h]”hŒ.same as N, the first GPIO managed by this chip”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K€hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j)  hjÿ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h K€hjü  ubj  )”}”(hŒ9"label" ...
provided for diagnostics (not always unique)
”h]”(j  )”}”(hŒ"label" ...”h]”hŒâ€œlabelâ€ ...”…””}”(hj2  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h Kƒhj.  ubj*  )”}”(hhh]”h¾)”}”(hŒ,provided for diagnostics (not always unique)”h]”hŒ,provided for diagnostics (not always unique)”…””}”(hjC  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Kƒhj@  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j)  hj.  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h Kƒhjü  ubj  )”}”(hŒ="ngpio" ...
how many GPIOs this manages (N to N + ngpio - 1)
”h]”(j  )”}”(hŒ"ngpio" ...”h]”hŒâ€œngpioâ€ ...”…””}”(hja  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h K†hj]  ubj*  )”}”(hhh]”h¾)”}”(hŒ0how many GPIOs this manages (N to N + ngpio - 1)”h]”hŒ0how many GPIOs this manages (N to N + ngpio - 1)”…””}”(hjr  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K†hjo  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j)  hj]  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hŸh¶h K†hjü  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  hjø  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jy  hŸh¶h Khjæ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jy  hŸh¶h K}hjZ  hžhubh¾)”}”(hX“  Board documentation should in most cases cover what GPIOs are used for
what purposes. However, those numbers are not always stable; GPIOs on
a daughtercard might be different depending on the base board being used,
or other cards in the stack. In such cases, you may need to use the
gpiochip nodes (possibly in conjunction with schematics) to determine
the correct GPIO number to use for a given signal.”h]”hX“  Board documentation should in most cases cover what GPIOs are used for
what purposes. However, those numbers are not always stable; GPIOs on
a daughtercard might be different depending on the base board being used,
or other cards in the stack. In such cases, you may need to use the
gpiochip nodes (possibly in conjunction with schematics) to determine
the correct GPIO number to use for a given signal.”…””}”(hjž  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KˆhjZ  hžhubeh}”(h]”Œpaths-in-sysfs”ah ]”h"]”Œpaths in sysfs”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K,ubh¢)”}”(hhh]”(h§)”}”(hŒExporting from Kernel code”h]”hŒExporting from Kernel code”…””}”(hj·  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj´  hžhhŸh¶h K‘ubh¾)”}”(hŒkKernel code can explicitly manage exports of GPIOs which have already been
requested using gpio_request()::”h]”hŒjKernel code can explicitly manage exports of GPIOs which have already been
requested using gpio_request():”…””}”(hjÅ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K’hj´  hžhubhŒliteral_block”“”)”}”(hXI  /* export the GPIO to userspace */
int gpiod_export(struct gpio_desc *desc, bool direction_may_change);

/* reverse gpiod_export() */
void gpiod_unexport(struct gpio_desc *desc);

/* create a sysfs link to an exported GPIO node */
int gpiod_export_link(struct device *dev, const char *name,
              struct gpio_desc *desc);”h]”hXI  /* export the GPIO to userspace */
int gpiod_export(struct gpio_desc *desc, bool direction_may_change);

/* reverse gpiod_export() */
void gpiod_unexport(struct gpio_desc *desc);

/* create a sysfs link to an exported GPIO node */
int gpiod_export_link(struct device *dev, const char *name,
              struct gpio_desc *desc);”…””}”hjÕ  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1jÓ  hŸh¶h K•hj´  hžhubh¾)”}”(hX  After a kernel driver requests a GPIO, it may only be made available in
the sysfs interface by gpiod_export(). The driver can control whether the
signal direction may change. This helps drivers prevent userspace code
from accidentally clobbering important system state.”h]”hX  After a kernel driver requests a GPIO, it may only be made available in
the sysfs interface by gpiod_export(). The driver can control whether the
signal direction may change. This helps drivers prevent userspace code
from accidentally clobbering important system state.”…””}”(hjå  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KŸhj´  hžhubh¾)”}”(hŒÊThis explicit exporting can help with debugging (by making some kinds
of experiments easier), or can provide an always-there interface that's
suitable for documenting as part of a board support package.”h]”hŒÌThis explicit exporting can help with debugging (by making some kinds
of experiments easier), or can provide an always-there interface thatâ€™s
suitable for documenting as part of a board support package.”…””}”(hjó  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K¤hj´  hžhubh¾)”}”(hŒåAfter the GPIO has been exported, gpiod_export_link() allows creating
symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can
use this to provide the interface under their own device in sysfs with
a descriptive name.”h]”hŒåAfter the GPIO has been exported, gpiod_export_link() allows creating
symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can
use this to provide the interface under their own device in sysfs with
a descriptive name.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K¨hj´  hžhubeh}”(h]”Œexporting-from-kernel-code”ah ]”h"]”Œexporting from kernel code”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K‘ubeh}”(h]”Œ"gpio-sysfs-interface-for-userspace”ah ]”h"]”Œ"gpio sysfs interface for userspace”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”jB  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h¶Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j  j  jW  jT  j±  j®  j  j  uŒ	nametypes”}”(j  ‰jW  ‰j±  ‰j  ‰uh}”(j  h£jT  hïj®  jZ  j  j´  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.