Apache NuttX is a mature, real-time embedded operating system (RTOS) https://nuttx.apache.org/
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drivers/power: Describe the regulators through procfs.
The regulator framework has no way out to userspace: consumers reach a
rail by name from inside the kernel, which is the right interface for
controlling one, but it leaves a board with regulators offering no way
to see what they are doing, and a newly written regulator driver cannot
be looked at without writing a consumer for it first.

Adds /proc/regulator, behind REGULATOR_PROCFS, listing every registered
regulator: its present voltage, the range it will accept, whether it is
enabled, how many consumers hold and enable it, its supply, and whether
it is always on or expected on at boot.  Lines carry the same key:value
tokens in the same order, so the file is machine parseable.  The last
two are worth reading beside the consumer count, since a rail enabled
with no consumers is expected rather than suspect when either is set.

A part usually measures more than the framework has fields for, so
struct regulator_ops_s gains an optional describe method: it writes
key:value text and the renderer appends it to that rail's line.  This is
how a driver reports what only it knows, an input voltage, an output
current, a temperature or a fault word, without the framework growing a
field per part or the driver growing procfs code of its own.  It is
called with the list mutex held and never from interrupt context, so
reading the part over a bus is allowed.

The voltage and the enabled state are read back from the hardware rather
than recalled, so a rail the boot loader set and nothing has touched
since reads as it actually is.  Both calls can fail, and a failure
reports - rather than an errno formatted as a voltage or a rail that
looks switched on.

Reading the hardware is also why this takes the list mutex directly
rather than calling regulator_list_lock(), which additionally disables
interrupts so that callers in interrupt or idle context are safe.
Asking a regulator on a bus what it is doing means a transfer, and a
transfer waits; a task reading a file can afford to wait and an
interrupt handler cannot.

procfs_register() appends without checking for duplicates, so the entry
is claimed once for the lifetime of the system rather than whenever the
list is empty.  It also needs FS_PROCFS_REGISTER, which the option now
depends on rather than only FS_PROCFS.

Documents the framework, which had no page at all: the consumer
interface and what counted enables mean, what a driver supplies, and the
new entry.

The entry is read only.  What voltage a rail may be is knowledge its
consumers hold, and arranging the order between them is what the
framework is for, so moving one from a shell would step around the part
that matters.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Justin Hammond <justin@dynam.ac>
2026-08-18 17:28:02 +08:00
.github ci: do not trigger Build on PR description edits 2026-08-16 19:08:58 -04:00
arch arch/arm/stm32: use common SYSTICK_HCLKd8 symbol 2026-08-18 09:34:58 +08:00
audio audio: limit the buffer count guard to shared ring requests 2026-08-05 07:58:53 +02:00
binfmt sched: add supplementary group IDs (setgroups/getgroups/initgroups) 2026-08-12 16:06:03 -03:00
boards sched,fs,docs: support setuid sudo helper 2026-08-18 15:57:52 +08:00
cmake sched,fs,docs: support setuid sudo helper 2026-08-18 15:57:52 +08:00
crypto tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
Documentation drivers/power: Describe the regulators through procfs. 2026-08-18 17:28:02 +08:00
drivers drivers/power: Describe the regulators through procfs. 2026-08-18 17:28:02 +08:00
dummy build: add initial cmake build system 2023-07-08 13:50:48 +08:00
fs sched,fs,docs: support setuid sudo helper 2026-08-18 15:57:52 +08:00
graphics tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
include drivers/power: Describe the regulators through procfs. 2026-08-18 17:28:02 +08:00
libs libs/libc/machine/risc-v: Compare a register at a time on equal offsets. 2026-08-17 12:24:06 +02:00
mm cmake: Use NUTTX(_DIR/_BIN_DIR) instead CMAKE(_SRC_DIR/_BIN_DIR) 2026-08-09 11:13:08 -03:00
net net/arp: do not resolve an address to another interface's MAC 2026-08-17 11:28:45 +08:00
openamp cmake: Use NUTTX(_DIR/_BIN_DIR) instead CMAKE(_SRC_DIR/_BIN_DIR) 2026-08-09 11:13:08 -03:00
pass1 tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
sched sched,fs,docs: support setuid sudo helper 2026-08-18 15:57:52 +08:00
syscall sched: add supplementary group IDs (setgroups/getgroups/initgroups) 2026-08-12 16:06:03 -03:00
tools sched,fs,docs: support setuid sudo helper 2026-08-18 15:57:52 +08:00
video tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
wireless wireless/bluetooth/bt_hcicore.c: Balance conn and buffer refs in hci_acl(). 2026-08-15 11:51:19 +08:00
.asf.yaml github: master branch protection tune. 2025-05-07 18:37:13 -05:00
.codespell-ignore-lines arch/arm: Reserve r10 via ARCHCFLAGS and hoist the PIC module flags. 2026-07-24 23:09:08 +08:00
.codespellrc arch/arm/rp23xx: Add hardware TRNG driver for /dev/random. 2026-07-25 15:06:56 +08:00
.editorconfig .editorconfig: fix character encoding property specification 2025-11-28 19:12:13 +08:00
.gitignore git: Specify multiple build directories in .gitignore. 2026-05-20 03:06:58 +08:00
.gitmessage docs/contributing: Add a commit message template 2025-06-03 17:33:24 +08:00
.pre-commit-config.yaml pre-commit: enable codespell checks 2025-05-05 12:34:39 +08:00
.yamllint feat: add a GitHub action to lint the YAML files 2020-12-15 09:52:04 -06:00
AUTHORS AUTHORS: add Eren Terzioglu 2026-05-20 15:17:00 +08:00
CMakeLists.txt Revert "cmake: normalize .config on reconfigure" 2026-08-13 07:54:00 +02:00
CONTRIBUTING.md contributing: Add requirement for 'Assisted-by' commit field 2026-07-12 09:42:28 +08:00
INVIOLABLES.md INVIOLABLES.md: Fix a simple alignment and change occurrences of Nuttx 2020-09-03 01:33:05 +08:00
Kconfig drivers/clk: Add debug output levels. 2026-08-16 23:23:04 +08:00
LICENSE libs/libdsp: Add Matrix operations 2026-07-11 14:55:59 -03:00
Makefile !boards: enforce secure ROMFS passwd and TEA key setup 2026-07-09 22:41:11 +08:00
NOTICE Remove the double blank line from source files 2022-02-20 20:10:14 +01:00
README.md ci/testing: Add MemBrowse Integration 2026-06-18 12:07:41 -03:00
ReleaseNotes Documentation: move ReleaseNotes 2023-09-26 20:41:00 +08:00

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Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).

For brevity, many parts of the documentation will refer to Apache NuttX as simply NuttX.

Getting Started

First time on NuttX? Read the Getting Started guide! If you don't have a board available, NuttX has its own simulator that you can run on terminal.

Documentation

You can find the current NuttX documentation on the Documentation Page.

Alternatively, you can build the documentation yourself by following the Documentation Build Instructions.

The old NuttX documentation is still available in the Apache wiki.

Supported Boards

NuttX supports a wide variety of platforms. See the full list on the Supported Platforms page.

Contributing

If you wish to contribute to the NuttX project, read the Contributing guidelines for information on Git usage, coding standard, workflow and the NuttX principles.

License

The code in this repository is under either the Apache 2 license, or a license compatible with the Apache 2 license. See the License Page for more information.