gpio_cdev/lib.rs
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// Copyright (c) 2018 The rust-gpio-cdev Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! The `gpio-cdev` crate provides access to the [GPIO character device
//! ABI](https://www.kernel.org/doc/Documentation/ABI/testing/gpio-cdev). This API,
//! stabilized with Linux v4.4, deprecates the legacy sysfs interface to GPIOs that is
//! planned to be removed from the upstream kernel after
//! year 2020 (which is coming up quickly).
//!
//! This crate attempts to wrap this interface in a moderately direction fashion
//! while retaining safety and using Rust idioms (where doing so could be mapped
//! to the underlying abstraction without significant overhead or loss of
//! functionality).
//!
//! For additional context for why the kernel is moving from the sysfs API to the
//! character device API, please see the main [README on Github].
//!
//! # Examples
//!
//! The following example reads the state of a GPIO line/pin and writes the matching
//! state to another line/pin.
//!
//! ```no_run
//! use gpio_cdev::{Chip, LineRequestFlags, EventRequestFlags, EventType};
//!
//! // Lines are offset within gpiochip0; see docs for more info on chips/lines
//! fn mirror_gpio(inputline: u32, outputline: u32) -> Result<(), gpio_cdev::Error> {
//! let mut chip = Chip::new("/dev/gpiochip0")?;
//! let input = chip.get_line(inputline)?;
//! let output = chip.get_line(outputline)?;
//! let output_handle = output.request(LineRequestFlags::OUTPUT, 0, "mirror-gpio")?;
//! for event in input.events(
//! LineRequestFlags::INPUT,
//! EventRequestFlags::BOTH_EDGES,
//! "mirror-gpio",
//! )? {
//! let evt = event?;
//! println!("{:?}", evt);
//! match evt.event_type() {
//! EventType::RisingEdge => {
//! output_handle.set_value(1)?;
//! }
//! EventType::FallingEdge => {
//! output_handle.set_value(0)?;
//! }
//! }
//! }
//!
//! Ok(())
//! }
//!
//! # fn main() -> Result<(), gpio_cdev::Error> {
//! # mirror_gpio(0, 1)
//! # }
//! ```
//!
//! To get the state of a GPIO Line on a given chip:
//!
//! ```no_run
//! use gpio_cdev::{Chip, LineRequestFlags};
//!
//! # fn main() -> Result<(), gpio_cdev::Error> {
//! // Read the state of GPIO4 on a raspberry pi. /dev/gpiochip0
//! // maps to the driver for the SoC (builtin) GPIO controller.
//! // The LineHandle returned by request must be assigned to a
//! // variable (in this case the variable handle) to ensure that
//! // the corresponding file descriptor is not closed.
//! let mut chip = Chip::new("/dev/gpiochip0")?;
//! let handle = chip
//! .get_line(4)?
//! .request(LineRequestFlags::INPUT, 0, "read-input")?;
//! for _ in 1..4 {
//! println!("Value: {:?}", handle.get_value()?);
//! }
//! # Ok(()) }
//! ```
//!
//! [README on Github]: https://github.com/rust-embedded/rust-gpio-cdev
#![cfg_attr(docsrs, feature(doc_cfg))]
#[macro_use]
extern crate bitflags;
#[macro_use]
extern crate nix;
use std::cmp::min;
use std::ffi::CStr;
use std::fs::{read_dir, File, ReadDir};
use std::io::Read;
use std::mem;
use std::ops::Index;
use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, RawFd};
use std::path::{Path, PathBuf};
use std::ptr;
use std::slice;
use std::sync::Arc;
#[cfg(feature = "async-tokio")]
#[cfg_attr(docsrs, doc(cfg(feature = "async-tokio")))]
mod async_tokio;
pub mod errors; // pub portion is deprecated
mod ffi;
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum IoctlKind {
ChipInfo,
LineInfo,
LineHandle,
LineEvent,
GetLine,
SetLine,
}
#[cfg(feature = "async-tokio")]
#[cfg_attr(docsrs, doc(cfg(feature = "async-tokio")))]
pub use crate::async_tokio::AsyncLineEventHandle;
pub use errors::*;
unsafe fn rstr_lcpy(dst: *mut libc::c_char, src: &str, length: usize) {
let copylen = min(src.len() + 1, length);
ptr::copy_nonoverlapping(src.as_bytes().as_ptr().cast(), dst, copylen - 1);
slice::from_raw_parts_mut(dst, length)[copylen - 1] = 0;
}
#[derive(Debug)]
struct InnerChip {
pub path: PathBuf,
pub file: File,
pub name: String,
pub label: String,
pub lines: u32,
}
/// A GPIO Chip maps to the actual device driver instance in hardware that
/// one interacts with to interact with individual GPIOs. Often these chips
/// map to IP chunks on an SoC but could also be enumerated within the kernel
/// via something like a PCI or USB bus.
///
/// The Linux kernel itself enumerates GPIO character devices at two paths:
/// 1. `/dev/gpiochipN`
/// 2. `/sys/bus/gpiochipN`
///
/// It is best not to assume that a device will always be enumerated in the
/// same order (especially if it is connected via a bus). In order to reliably
/// find the correct chip, there are a few approaches that one could reasonably
/// take:
///
/// 1. Create a udev rule that will match attributes of the device and
/// setup a symlink to the device.
/// 2. Iterate over all available chips using the [`chips()`] call to find the
/// device with matching criteria.
/// 3. For simple cases, just using the enumerated path is fine (demo work). This
/// is discouraged for production.
///
/// [`chips()`]: fn.chips.html
#[derive(Debug)]
pub struct Chip {
inner: Arc<InnerChip>,
}
/// Iterator over chips
#[derive(Debug)]
pub struct ChipIterator {
readdir: ReadDir,
}
impl Iterator for ChipIterator {
type Item = Result<Chip>;
fn next(&mut self) -> Option<Result<Chip>> {
for entry in &mut self.readdir {
match entry {
Ok(entry) => {
if entry
.path()
.as_path()
.to_string_lossy()
.contains("gpiochip")
{
return Some(Chip::new(entry.path()));
}
}
Err(e) => {
return Some(Err(e.into()));
}
}
}
None
}
}
/// Iterate over all GPIO chips currently present on this system
pub fn chips() -> Result<ChipIterator> {
Ok(ChipIterator {
readdir: read_dir("/dev")?,
})
}
impl Chip {
/// Open the GPIO Chip at the provided path (e.g. `/dev/gpiochip<N>`)
pub fn new<P: AsRef<Path>>(path: P) -> Result<Self> {
let f = File::open(path.as_ref())?;
let mut info: ffi::gpiochip_info = unsafe { mem::zeroed() };
ffi::gpio_get_chipinfo_ioctl(f.as_raw_fd(), &mut info)?;
Ok(Self {
inner: Arc::new(InnerChip {
file: f,
path: path.as_ref().to_path_buf(),
name: unsafe {
CStr::from_ptr(info.name.as_ptr())
.to_string_lossy()
.into_owned()
},
label: unsafe {
CStr::from_ptr(info.label.as_ptr())
.to_string_lossy()
.into_owned()
},
lines: info.lines,
}),
})
}
/// Get the fs path of this character device (e.g. `/dev/gpiochipN`)
pub fn path(&self) -> &Path {
self.inner.path.as_path()
}
/// The name of the device driving this GPIO chip in the kernel
pub fn name(&self) -> &str {
self.inner.name.as_str()
}
/// A functional name for this GPIO chip, such as a product number. Might
/// be an empty string.
///
/// As an example, the SoC GPIO chip on a Raspberry Pi is "pinctrl-bcm2835"
pub fn label(&self) -> &str {
self.inner.label.as_str()
}
/// The number of lines/pins indexable through this chip
///
/// Not all of these may be usable depending on how the hardware is
/// configured/muxed.
pub fn num_lines(&self) -> u32 {
self.inner.lines
}
/// Get a handle to the GPIO line at a given offset
///
/// The actual physical line corresponding to a given offset
/// is completely dependent on how the driver/hardware for
/// the chip works as well as the associated board layout.
///
/// For a device like the NXP i.mx6 SoC GPIO controller there
/// are several banks of GPIOs with each bank containing 32
/// GPIOs. For this hardware and driver something like
/// `GPIO2_5` would map to offset 37.
pub fn get_line(&mut self, offset: u32) -> Result<Line> {
Line::new(self.inner.clone(), offset)
}
/// Get a handle to multiple GPIO line at a given offsets
///
/// The group of lines can be manipulated simultaneously.
pub fn get_lines(&mut self, offsets: &[u32]) -> Result<Lines> {
Lines::new(self.inner.clone(), offsets)
}
/// Get a handle to all the GPIO lines on the chip
///
/// The group of lines can be manipulated simultaneously.
pub fn get_all_lines(&mut self) -> Result<Lines> {
let offsets: Vec<u32> = (0..self.num_lines()).collect();
self.get_lines(&offsets)
}
/// Get an interator over all lines that can be potentially access for this
/// chip.
pub fn lines(&self) -> LineIterator {
LineIterator {
chip: self.inner.clone(),
idx: 0,
}
}
}
/// Iterator over GPIO Lines for a given chip.
#[derive(Debug)]
pub struct LineIterator {
chip: Arc<InnerChip>,
idx: u32,
}
impl Iterator for LineIterator {
type Item = Line;
fn next(&mut self) -> Option<Line> {
if self.idx < self.chip.lines {
let idx = self.idx;
self.idx += 1;
// Since we checked the index, we know this will be Ok
Some(Line::new(self.chip.clone(), idx).unwrap())
} else {
None
}
}
}
/// Access to a specific GPIO Line
///
/// GPIO Lines must be obtained through a parent [`Chip`] and
/// represent an actual GPIO pin/line accessible via that chip.
/// Not all accessible lines for a given chip may actually
/// map to hardware depending on how the board is setup
/// in the kernel.
///
#[derive(Debug, Clone)]
pub struct Line {
chip: Arc<InnerChip>,
offset: u32,
}
/// Information about a specific GPIO Line
///
/// Wraps kernel [`struct gpioline_info`].
///
/// [`struct gpioline_info`]: https://elixir.bootlin.com/linux/v4.9.127/source/include/uapi/linux/gpio.h#L36
#[derive(Debug)]
pub struct LineInfo {
line: Line,
flags: LineFlags,
name: Option<String>,
consumer: Option<String>,
}
bitflags! {
/// Line Request Flags
///
/// Maps to kernel [`GPIOHANDLE_REQUEST_*`] flags.
///
/// [`GPIOHANDLE_REQUEST_*`]: https://elixir.bootlin.com/linux/v4.9.127/source/include/uapi/linux/gpio.h#L58
#[derive(Debug, Clone)]
pub struct LineRequestFlags: u32 {
const INPUT = (1 << 0);
const OUTPUT = (1 << 1);
const ACTIVE_LOW = (1 << 2);
const OPEN_DRAIN = (1 << 3);
const OPEN_SOURCE = (1 << 4);
}
}
bitflags! {
/// Event request flags
///
/// Maps to kernel [`GPIOEVENT_REQEST_*`] flags.
///
/// [`GPIOEVENT_REQUEST_*`]: https://elixir.bootlin.com/linux/v4.9.127/source/include/uapi/linux/gpio.h#L109
pub struct EventRequestFlags: u32 {
const RISING_EDGE = (1 << 0);
const FALLING_EDGE = (1 << 1);
const BOTH_EDGES = Self::RISING_EDGE.bits() | Self::FALLING_EDGE.bits();
}
}
bitflags! {
/// Informational Flags
///
/// Maps to kernel [`GPIOLINE_FLAG_*`] flags.
///
/// [`GPIOLINE_FLAG_*`]: https://elixir.bootlin.com/linux/v4.9.127/source/include/uapi/linux/gpio.h#L29
#[derive(Debug)]
pub struct LineFlags: u32 {
const KERNEL = (1 << 0);
const IS_OUT = (1 << 1);
const ACTIVE_LOW = (1 << 2);
const OPEN_DRAIN = (1 << 3);
const OPEN_SOURCE = (1 << 4);
}
}
/// In or Out
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum LineDirection {
In,
Out,
}
unsafe fn cstrbuf_to_string(buf: &[libc::c_char]) -> Option<String> {
if buf[0] == 0 {
None
} else {
Some(CStr::from_ptr(buf.as_ptr()).to_string_lossy().into_owned())
}
}
impl Line {
fn new(chip: Arc<InnerChip>, offset: u32) -> Result<Self> {
if offset >= chip.lines {
return Err(offset_err(offset));
}
Ok(Self { chip, offset })
}
/// Get info about the line from the kernel.
pub fn info(&self) -> Result<LineInfo> {
let mut line_info = ffi::gpioline_info {
line_offset: self.offset,
flags: 0,
name: [0; 32],
consumer: [0; 32],
};
ffi::gpio_get_lineinfo_ioctl(self.chip.file.as_raw_fd(), &mut line_info)?;
Ok(LineInfo {
line: self.clone(),
flags: LineFlags::from_bits_truncate(line_info.flags),
name: unsafe { cstrbuf_to_string(&line_info.name[..]) },
consumer: unsafe { cstrbuf_to_string(&line_info.consumer[..]) },
})
}
/// Offset of this line within its parent chip
pub fn offset(&self) -> u32 {
self.offset
}
/// Get a handle to this chip's parent
pub fn chip(&self) -> Chip {
Chip {
inner: self.chip.clone(),
}
}
/// Request access to interact with this line from the kernel
///
/// This is similar to the "export" operation present in the sysfs
/// API with the key difference that we are also able to configure
/// the GPIO with `flags` to specify how the line will be used
/// at the time of request.
///
/// For an output, the `default` parameter specifies the value
/// the line should have when it is configured as an output. The
/// `consumer` string should describe the process consuming the
/// line (this will be truncated to 31 characters if too long).
///
/// # Errors
///
/// The main source of errors here is if the kernel returns an
/// error to the ioctl performing the request here. This will
/// result in an [`Error`] being returned with [`ErrorKind::Ioctl`].
///
/// One possible cause for an error here would be if the line is
/// already in use. One can check for this prior to making the
/// request using [`is_kernel`].
///
/// [`Error`]: errors/struct.Error.html
/// [`ErrorKind::Ioctl`]: errors/enum.ErrorKind.html#variant.Ioctl
/// [`is_kernel`]: struct.Line.html#method.is_kernel
pub fn request(
&self,
flags: LineRequestFlags,
default: u8,
consumer: &str,
) -> Result<LineHandle> {
// prepare the request; the kernel consumes some of these values and will
// set the fd for us.
let mut request = ffi::gpiohandle_request {
lineoffsets: unsafe { mem::zeroed() },
flags: flags.bits(),
default_values: unsafe { mem::zeroed() },
consumer_label: unsafe { mem::zeroed() },
lines: 1,
fd: 0,
};
request.lineoffsets[0] = self.offset;
request.default_values[0] = default;
unsafe {
rstr_lcpy(
request.consumer_label[..].as_mut_ptr(),
consumer,
request.consumer_label.len(),
);
}
ffi::gpio_get_linehandle_ioctl(self.chip.file.as_raw_fd(), &mut request)?;
Ok(LineHandle {
line: self.clone(),
flags,
file: unsafe { File::from_raw_fd(request.fd) },
})
}
/// Get an event handle that can be used as a blocking iterator over
/// the events (state changes) for this Line
///
/// When used as an iterator, it blocks while there is not another event
/// available from the kernel for this line matching the subscription
/// criteria specified in the `event_flags`. The line will be configured
/// with the specified `handle_flags` and `consumer` label.
///
/// Note that as compared with the sysfs interface, the character
/// device interface maintains a queue of events in the kernel so
/// events may happen (e.g. a line changing state faster than can
/// be picked up in userspace in real-time). These events will be
/// returned on the iterator in order with the event containing the
/// associated timestamp attached with high precision within the
/// kernel (from an ISR for most drivers).
///
/// # Example
///
/// ```no_run
/// # fn main() -> Result<(), gpio_cdev::Error> {
/// use gpio_cdev::{Chip, LineRequestFlags, EventRequestFlags};
/// use std::io;
///
/// let mut chip = Chip::new("/dev/gpiochip0")?;
/// let input = chip.get_line(0)?;
///
/// // Show all state changes for this line forever
/// for event in input.events(
/// LineRequestFlags::INPUT,
/// EventRequestFlags::BOTH_EDGES,
/// "rust-gpio"
/// )? {
/// println!("{:?}", event?);
/// }
/// # Ok(())
/// # }
/// ```
pub fn events(
&self,
handle_flags: LineRequestFlags,
event_flags: EventRequestFlags,
consumer: &str,
) -> Result<LineEventHandle> {
let mut request = ffi::gpioevent_request {
lineoffset: self.offset,
handleflags: handle_flags.bits(),
eventflags: event_flags.bits(),
consumer_label: unsafe { mem::zeroed() },
fd: 0,
};
unsafe {
rstr_lcpy(
request.consumer_label[..].as_mut_ptr(),
consumer,
request.consumer_label.len(),
);
}
ffi::gpio_get_lineevent_ioctl(self.chip.file.as_raw_fd(), &mut request)?;
Ok(LineEventHandle {
line: self.clone(),
file: unsafe { File::from_raw_fd(request.fd) },
})
}
#[cfg(feature = "async-tokio")]
#[cfg_attr(docsrs, doc(cfg(feature = "async-tokio")))]
pub fn async_events(
&self,
handle_flags: LineRequestFlags,
event_flags: EventRequestFlags,
consumer: &str,
) -> Result<AsyncLineEventHandle> {
let events = self.events(handle_flags, event_flags, consumer)?;
AsyncLineEventHandle::new(events)
}
}
impl LineInfo {
/// Get a handle to the line that this info represents
pub fn line(&self) -> &Line {
&self.line
}
/// Name assigned to this chip if assigned
pub fn name(&self) -> Option<&str> {
self.name.as_deref()
}
/// The name of this GPIO line, such as the output pin of the line on the
/// chip, a rail or a pin header name on a board, as specified by the gpio
/// chip.
pub fn consumer(&self) -> Option<&str> {
self.consumer.as_deref()
}
/// Get the direction of this GPIO if configured
///
/// Lines are considered to be inputs if not explicitly
/// marked as outputs in the line info flags by the kernel.
pub fn direction(&self) -> LineDirection {
if self.flags.contains(LineFlags::IS_OUT) {
LineDirection::Out
} else {
LineDirection::In
}
}
/// True if the any flags for the device are set (input or output)
pub fn is_used(&self) -> bool {
!self.flags.is_empty()
}
/// True if this line is being used by something else in the kernel
///
/// If another driver or subsystem in the kernel is using the line
/// then it cannot be used via the cdev interface. See [relevant kernel code].
///
/// [relevant kernel code]: https://elixir.bootlin.com/linux/v4.9.127/source/drivers/gpio/gpiolib.c#L938
pub fn is_kernel(&self) -> bool {
self.flags.contains(LineFlags::KERNEL)
}
/// True if this line is marked as active low in the kernel
pub fn is_active_low(&self) -> bool {
self.flags.contains(LineFlags::ACTIVE_LOW)
}
/// True if this line is marked as open drain in the kernel
pub fn is_open_drain(&self) -> bool {
self.flags.contains(LineFlags::OPEN_DRAIN)
}
/// True if this line is marked as open source in the kernel
pub fn is_open_source(&self) -> bool {
self.flags.contains(LineFlags::OPEN_SOURCE)
}
}
/// Handle for interacting with a "requested" line
///
/// In order for userspace to read/write the value of a GPIO
/// it must be requested from the chip using [`Line::request`].
/// On success, the kernel creates an anonymous file descriptor
/// for interacting with the requested line. This structure
/// is the go-between for callers and that file descriptor.
///
/// [`Line::request`]: struct.Line.html#method.request
#[derive(Debug)]
pub struct LineHandle {
line: Line,
flags: LineRequestFlags,
file: File,
}
impl LineHandle {
/// Request the current state of this Line from the kernel
///
/// This call is expected to succeed for both input and output
/// lines. It should be noted, however, that some drivers may
/// not be able to give any useful information when the value
/// is requested for an output line.
///
/// This value should be 0 or 1 which a "1" representing that
/// the line is active. Usually this means that the line is
/// at logic-level high but it could mean the opposite if the
/// line has been marked as being `ACTIVE_LOW`.
pub fn get_value(&self) -> Result<u8> {
let mut data: ffi::gpiohandle_data = unsafe { mem::zeroed() };
ffi::gpiohandle_get_line_values_ioctl(self.file.as_raw_fd(), &mut data)?;
Ok(data.values[0])
}
/// Request that the line be driven to the specified value
///
/// The value should be 0 or 1 with 1 representing a request
/// to make the line "active". Usually "active" means
/// logic level high unless the line has been marked as `ACTIVE_LOW`.
///
/// Calling `set_value` on a line that is not an output will
/// likely result in an error (from the kernel).
pub fn set_value(&self, value: u8) -> Result<()> {
let mut data: ffi::gpiohandle_data = unsafe { mem::zeroed() };
data.values[0] = value;
ffi::gpiohandle_set_line_values_ioctl(self.file.as_raw_fd(), &mut data)?;
Ok(())
}
/// Get the Line information associated with this handle.
pub fn line(&self) -> &Line {
&self.line
}
/// Get the flags with which this handle was created
pub fn flags(&self) -> LineRequestFlags {
self.flags.clone()
}
}
impl AsRawFd for LineHandle {
/// Gets the raw file descriptor for the `LineHandle`.
fn as_raw_fd(&self) -> RawFd {
self.file.as_raw_fd()
}
}
/// A collection of lines that can be accesses simultaneously
///
/// This is a collection of lines, all from the same GPIO chip that can
/// all be accessed simultaneously
#[derive(Debug)]
pub struct Lines {
lines: Vec<Line>,
}
impl Lines {
fn new(chip: Arc<InnerChip>, offsets: &[u32]) -> Result<Self> {
let res: Result<Vec<Line>> = offsets
.iter()
.map(|off| Line::new(chip.clone(), *off))
.collect();
let lines = res?;
Ok(Self { lines })
}
/// Get a handle to the parent chip for the lines
pub fn chip(&self) -> Chip {
self.lines[0].chip()
}
/// Get the number of lines in the collection
pub fn is_empty(&self) -> bool {
self.lines.is_empty()
}
/// Get the number of lines in the collection
pub fn len(&self) -> usize {
self.lines.len()
}
/// Request access to interact with these lines from the kernel
///
/// This is similar to the "export" operation present in the sysfs
/// API with the key difference that we are also able to configure
/// the GPIO with `flags` to specify how the line will be used
/// at the time of request.
///
/// For an output, the `default` parameter specifies the value
/// each line should have when it is configured as an output. The
/// `consumer` string should describe the process consuming the
/// line (this will be truncated to 31 characters if too long).
///
/// # Errors
///
/// The main source of errors here is if the kernel returns an
/// error to the ioctl performing the request here. This will
/// result in an [`Error`] being returned with [`ErrorKind::Ioctl`].
///
/// One possible cause for an error here would be if the lines are
/// already in use. One can check for this prior to making the
/// request using [`is_kernel`].
///
/// [`Error`]: errors/struct.Error.html
/// [`ErrorKind::Ioctl`]: errors/enum.ErrorKind.html#variant.Ioctl
/// [`is_kernel`]: struct.Line.html#method.is_kernel
pub fn request(
&self,
flags: LineRequestFlags,
default: &[u8],
consumer: &str,
) -> Result<MultiLineHandle> {
let n = self.lines.len();
if default.len() != n {
return Err(invalid_err(n, default.len()));
}
// prepare the request; the kernel consumes some of these values and will
// set the fd for us.
let mut request = ffi::gpiohandle_request {
lineoffsets: unsafe { mem::zeroed() },
flags: flags.bits(),
default_values: unsafe { mem::zeroed() },
consumer_label: unsafe { mem::zeroed() },
lines: n as u32,
fd: 0,
};
#[allow(clippy::needless_range_loop)] // clippy does not understand this loop correctly
for i in 0..n {
request.lineoffsets[i] = self.lines[i].offset();
request.default_values[i] = default[i];
}
unsafe {
rstr_lcpy(
request.consumer_label[..].as_mut_ptr(),
consumer,
request.consumer_label.len(),
);
}
ffi::gpio_get_linehandle_ioctl(self.lines[0].chip().inner.file.as_raw_fd(), &mut request)?;
let lines = self.lines.clone();
Ok(MultiLineHandle {
lines: Self { lines },
file: unsafe { File::from_raw_fd(request.fd) },
})
}
}
impl Index<usize> for Lines {
type Output = Line;
fn index(&self, i: usize) -> &Line {
&self.lines[i]
}
}
/// Handle for interacting with a "requested" line
///
/// In order for userspace to read/write the value of a GPIO
/// it must be requested from the chip using [`Line::request`].
/// On success, the kernel creates an anonymous file descriptor
/// for interacting with the requested line. This structure
/// is the go-between for callers and that file descriptor.
///
/// [`Line::request`]: struct.Line.html#method.request
#[derive(Debug)]
pub struct MultiLineHandle {
lines: Lines,
file: File,
}
impl MultiLineHandle {
/// Request the current state of this Line from the kernel
///
/// This call is expected to succeed for both input and output
/// lines. It should be noted, however, that some drivers may
/// not be able to give any useful information when the value
/// is requested for an output line.
///
/// This value should be 0 or 1 which a "1" representing that
/// the line is active. Usually this means that the line is
/// at logic-level high but it could mean the opposite if the
/// line has been marked as being `ACTIVE_LOW`.
pub fn get_values(&self) -> Result<Vec<u8>> {
let mut data: ffi::gpiohandle_data = unsafe { mem::zeroed() };
ffi::gpiohandle_get_line_values_ioctl(self.file.as_raw_fd(), &mut data)?;
let n = self.num_lines();
let values: Vec<u8> = (0..n).map(|i| data.values[i]).collect();
Ok(values)
}
/// Request that the line be driven to the specified value
///
/// The value should be 0 or 1 with 1 representing a request
/// to make the line "active". Usually "active" means
/// logic level high unless the line has been marked as `ACTIVE_LOW`.
///
/// Calling `set_value` on a line that is not an output will
/// likely result in an error (from the kernel).
pub fn set_values(&self, values: &[u8]) -> Result<()> {
let n = self.num_lines();
if values.len() != n {
return Err(invalid_err(n, values.len()));
}
let mut data: ffi::gpiohandle_data = unsafe { mem::zeroed() };
data.values[..n].clone_from_slice(&values[..n]);
ffi::gpiohandle_set_line_values_ioctl(self.file.as_raw_fd(), &mut data)?;
Ok(())
}
/// Get the number of lines associated with this handle
pub fn num_lines(&self) -> usize {
self.lines.len()
}
/// Get the Line information associated with this handle.
pub fn lines(&self) -> &Lines {
&self.lines
}
}
impl AsRawFd for MultiLineHandle {
/// Gets the raw file descriptor for the `LineHandle`.
fn as_raw_fd(&self) -> RawFd {
self.file.as_raw_fd()
}
}
/// Did the Line rise (go active) or fall (go inactive)?
///
/// Maps to kernel [`GPIOEVENT_EVENT_*`] definitions.
///
/// [`GPIOEVENT_EVENT_*`]: https://elixir.bootlin.com/linux/v4.9.127/source/include/uapi/linux/gpio.h#L136
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum EventType {
RisingEdge,
FallingEdge,
}
/// Information about a change to the state of a Line
///
/// Wraps kernel [`struct gpioevent_data`].
///
/// [`struct gpioevent_data`]: https://elixir.bootlin.com/linux/v4.9.127/source/include/uapi/linux/gpio.h#L142
pub struct LineEvent(ffi::gpioevent_data);
impl std::fmt::Debug for LineEvent {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
write!(
f,
"LineEvent {{ timestamp: {:?}, event_type: {:?} }}",
self.timestamp(),
self.event_type()
)
}
}
impl LineEvent {
/// Best estimate of event occurrence time, in nanoseconds
///
/// In most cases, the timestamp for the event is captured
/// in an interrupt handler so it should be very accurate.
///
/// The nanosecond timestamp value should are captured
/// using the `CLOCK_MONOTONIC` offsets in the kernel and
/// should be compared against `CLOCK_MONOTONIC` values.
/// Note that kernel versions prior to 5.7 used
/// `CLOCK_REALTIME` offsets instead.
pub fn timestamp(&self) -> u64 {
self.0.timestamp
}
/// Was this a rising or a falling edge?
pub fn event_type(&self) -> EventType {
if self.0.id == 0x01 {
EventType::RisingEdge
} else {
EventType::FallingEdge
}
}
}
/// Handle for retrieving events from the kernel for a line
///
/// In order for userspace to retrieve incoming events on a GPIO,
/// an event handle must be requested from the chip using
/// [`Line::events`].
/// On success, the kernel creates an anonymous file descriptor
/// for reading events. This structure is the go-between for callers
/// and that file descriptor.
///
/// [`Line::events`]: struct.Line.html#method.events
#[derive(Debug)]
pub struct LineEventHandle {
line: Line,
file: File,
}
impl LineEventHandle {
/// Retrieve the next event from the kernel for this line
///
/// This blocks while there is not another event available from the
/// kernel for the line which matches the subscription criteria
/// specified in the `event_flags` when the handle was created.
pub fn get_event(&mut self) -> Result<LineEvent> {
match self.read_event() {
Ok(Some(event)) => Ok(event),
Ok(None) => Err(event_err(nix::errno::Errno::EIO)),
Err(e) => Err(e.into()),
}
}
/// Request the current state of this Line from the kernel
///
/// This value should be 0 or 1 which a "1" representing that
/// the line is active. Usually this means that the line is
/// at logic-level high but it could mean the opposite if the
/// line has been marked as being `ACTIVE_LOW`.
pub fn get_value(&self) -> Result<u8> {
let mut data: ffi::gpiohandle_data = unsafe { mem::zeroed() };
ffi::gpiohandle_get_line_values_ioctl(self.file.as_raw_fd(), &mut data)?;
Ok(data.values[0])
}
/// Get the Line information associated with this handle.
pub fn line(&self) -> &Line {
&self.line
}
pub fn file(&self) -> &File {
&self.file
}
pub fn file2(&mut self) -> &File {
&self.file
}
/// Helper function which returns the line event if a complete event was read, Ok(None) if not
/// enough data was read or the error returned by `read()`.
pub(crate) fn read_event(&mut self) -> std::io::Result<Option<LineEvent>> {
let mut data: ffi::gpioevent_data = unsafe { mem::zeroed() };
let data_as_buf = unsafe {
slice::from_raw_parts_mut(
(&mut data as *mut ffi::gpioevent_data).cast(),
mem::size_of::<ffi::gpioevent_data>(),
)
};
let bytes_read = self.file.read(data_as_buf)?;
if bytes_read == mem::size_of::<ffi::gpioevent_data>() {
Ok(Some(LineEvent(data)))
} else {
Ok(None)
}
}
}
impl AsRawFd for LineEventHandle {
/// Gets the raw file descriptor for the `LineEventHandle`.
fn as_raw_fd(&self) -> RawFd {
self.file.as_raw_fd()
}
}
impl AsFd for LineEventHandle {
/// Gets the raw file descriptor for the `LineEventHandle`.
fn as_fd(&self) -> BorrowedFd<'_> {
self.file.as_fd()
}
}
impl Iterator for LineEventHandle {
type Item = Result<LineEvent>;
fn next(&mut self) -> Option<Result<LineEvent>> {
match self.read_event() {
Ok(None) => None,
Ok(Some(event)) => Some(Ok(event)),
Err(e) => Some(Err(e.into())),
}
}
}