fdt-raw 0.3.0

A low-level, no-std compatible library for parsing Flattened Device Tree (FDT) binary files
Documentation 
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//! Chosen node type for boot parameters.
//!
//! This module provides the `Chosen` type which represents the /chosen node
//! in the device tree, containing boot parameters and system configuration.

use core::ops::Deref;

use super::{Node, NodeBase};

/// The /chosen node containing boot parameters.
///
/// This node contains system configuration parameters chosen by the firmware
/// or bootloader, such as boot arguments, console paths, and other boot-time
/// settings.
#[derive(Clone)]
pub struct Chosen<'a> {
    node: NodeBase<'a>,
}

impl<'a> Chosen<'a> {
    /// Creates a new Chosen wrapper from a NodeBase.
    pub(crate) fn new(node: NodeBase<'a>) -> Self {
        Self { node }
    }

    /// Returns the bootargs property value.
    ///
    /// This property contains command-line arguments to be passed to the
    /// operating system kernel.
    pub fn bootargs(&self) -> Option<&'a str> {
        self.node.find_property_str("bootargs")
    }

    /// Returns the stdout-path property value.
    ///
    /// This property specifies the path to the device to be used for
    /// standard output (console).
    pub fn stdout_path(&self) -> Option<&'a str> {
        self.node.find_property_str("stdout-path")
    }

    /// Returns the node referenced by the stdout-path property.
    ///
    /// The device tree specification allows stdout-path to append options
    /// after a ':' separator, such as a UART baud rate. Those options are
    /// ignored when resolving the referenced node.
    pub fn stdout(&self) -> Option<Node<'a>> {
        let path = split_path_options(self.stdout_path()?);
        self.node._fdt.find_by_path(path)
    }

    /// Returns the stdin-path property value.
    ///
    /// This property specifies the path to the device to be used for
    /// standard input.
    pub fn stdin_path(&self) -> Option<&'a str> {
        self.node.find_property_str("stdin-path")
    }
}

impl<'a> Deref for Chosen<'a> {
    type Target = NodeBase<'a>;

    fn deref(&self) -> &Self::Target {
        &self.node
    }
}

impl core::fmt::Debug for Chosen<'_> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("Chosen")
            .field("bootargs", &self.bootargs())
            .field("stdout_path", &self.stdout_path())
            .finish()
    }
}

fn split_path_options(path: &str) -> &str {
    path.split_once(':').map_or(path, |(path, _)| path)
}

#[cfg(test)]
mod tests {
    use super::split_path_options;

    #[test]
    fn split_path_options_keeps_plain_path() {
        assert_eq!(split_path_options("/pl011@9000000"), "/pl011@9000000");
        assert_eq!(split_path_options("serial0"), "serial0");
    }

    #[test]
    fn split_path_options_removes_serial_options() {
        assert_eq!(
            split_path_options("/pl011@9000000:115200n8"),
            "/pl011@9000000"
        );
        assert_eq!(split_path_options("serial0:115200n8"), "serial0");
    }
}