1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
//! Crate for fetching and modifying the intel_pstate kernel parameters.
//!
//! # Example
//!
//! ```rust,no_run
//! use std::io;
//! use intel_pstate::PState;
//!
//! fn main() -> io::Result<()> {
//!     if let Ok(pstate) = PState::new() {
//!         pstate.set_min_perf_pct(50)?;
//!         pstate.set_max_perf_pct(100)?;
//!         pstate.set_no_turbo(false)?;
//!     }
//!
//!     Ok(())
//! }
//! ```

#[macro_use]
extern crate smart_default;

use std::io::{self, Read, Write};
use std::fmt::Display;
use std::fs::{File, OpenOptions};
use std::path::{Path, PathBuf};
use std::str::FromStr;

#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq, SmartDefault)]
/// A set of pstate values that was retrieved, or is to be set.
pub struct PStateValues {
    pub min_perf_pct: u8,
    #[default = "100"]
    pub max_perf_pct: u8,
    pub no_turbo: bool
}

/// Handle for fetching and modifying Intel PState kernel parameters.
/// 
/// # Note
/// 
/// - Currently, ony Linux is supported.
/// - Setting parameters will require root permissions.
pub struct PState {
    path: PathBuf,
}

impl PState {
    /// Attempt to fetch a handle to the Intel PState sysfs kernel instance.
    pub fn new() -> io::Result<PState> {
        let path = PathBuf::from("/sys/devices/system/cpu/intel_pstate");
        if path.is_dir() {
            Ok(PState { path })
        } else {
            Err(io::Error::new(io::ErrorKind::NotFound, "intel_pstate directory not found"))
        }
    }

    /// Get the minimum performance percent.
    pub fn min_perf_pct(&self) -> io::Result<u8> {
        parse_file(self.path.join("min_perf_pct"))
    }

    /// Set the minimum performance percent.
    pub fn set_min_perf_pct(&self, value: u8) -> io::Result<()> {
        write_file(self.path.join("min_perf_pct"), format!("{}", value))
    }

    /// Get the maximum performance percent.
    pub fn max_perf_pct(&self) -> io::Result<u8> {
        parse_file(self.path.join("max_perf_pct"))
    }

    /// Set the maximum performance percent.
    pub fn set_max_perf_pct(&self, value: u8) -> io::Result<()> {
        write_file(self.path.join("max_perf_pct"), format!("{}", value))
    }

    /// If true, this signifies that turbo is disabled.
    pub fn no_turbo(&self) -> io::Result<bool> {
        let value: u8 = parse_file(self.path.join("no_turbo"))?;
        Ok(value > 0)
    }

    /// Set the no_turbo value; `true` will disable turbo.
    pub fn set_no_turbo(&self, value: bool) -> io::Result<()> {
        write_file(self.path.join("no_turbo"), if value { "1" } else { "0" })
    }

    pub fn values(&self) -> io::Result<PStateValues> {
        let values = PStateValues {
            min_perf_pct: self.min_perf_pct()?,
            max_perf_pct: self.max_perf_pct()?,
            no_turbo: self.no_turbo()?
        };

        Ok(values)
    }

    /// Set all values in the given config.
    pub fn set_values(&self, values: PStateValues) -> io::Result<()> {
        self.set_min_perf_pct(values.min_perf_pct)?;
        self.set_max_perf_pct(values.max_perf_pct)?;
        self.set_no_turbo(values.no_turbo)
    }
}

fn read_file<P: AsRef<Path>>(path: P) -> io::Result<String> {
    let mut data = String::new();

    {
        let mut file = File::open(path.as_ref())?;
        file.read_to_string(&mut data)?;
    }

    Ok(data)
}

fn write_file<P: AsRef<Path>, S: AsRef<[u8]>>(path: P, data: S) -> io::Result<()> {
    {
        let mut file = OpenOptions::new().write(true).open(path)?;
        file.write_all(data.as_ref())?
    }

    Ok(())
}

fn parse_file<F: FromStr, P: AsRef<Path>>(path: P) -> io::Result<F> where F::Err: Display {
    read_file(path)?.trim().parse().map_err(|err| {
        io::Error::new(
            io::ErrorKind::InvalidData,
            format!("{}", err)
        )
    })
}