feature: add support for screenpad brightness

rog-platform/src/backlight.rs

@@ -0,0 +1,75 @@
+use std::path::PathBuf;
+
+use log::{info, warn};
+
+use crate::error::{PlatformError, Result};
+use crate::{attr_num, to_device};
+
+/// The "backlight" device provides access to screen brightness control
+#[derive(Debug, PartialEq, Eq, PartialOrd, Clone)]
+pub struct Backlight {
+    path: PathBuf,
+    device_type: BacklightType,
+}
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Clone)]
+pub enum BacklightType {
+    Primary,
+    Screenpad,
+}
+
+impl Backlight {
+    attr_num!("brightness", path, i32);
+
+    attr_num!("max_brightness", path, i32);
+
+    attr_num!("bl_power", path, i32);
+
+    pub fn new(device_type: BacklightType) -> Result<Self> {
+        let mut enumerator = udev::Enumerator::new().map_err(|err| {
+            warn!("{}", err);
+            PlatformError::Udev("enumerator failed".into(), err)
+        })?;
+        enumerator.match_subsystem("backlight").map_err(|err| {
+            warn!("{}", err);
+            PlatformError::Udev("match_subsystem failed".into(), err)
+        })?;
+
+        for device in enumerator.scan_devices().map_err(|err| {
+            warn!("{}", err);
+            PlatformError::Udev("scan_devices failed".into(), err)
+        })? {
+            info!("Backlight: Checking {:?}", device.syspath());
+            match device_type {
+                BacklightType::Primary => {
+                    if device.sysname().to_string_lossy() == "intel_backlight" {
+                        info!("Found primary backlight at {:?}", device.sysname());
+                        return Ok(Self {
+                            path: device.syspath().to_path_buf(),
+                            device_type,
+                        });
+                    }
+                }
+                BacklightType::Screenpad => {
+                    let name = device.sysname().to_string_lossy();
+                    if name == "asus_screenpad" || name == "asus_screenpad_backlight" {
+                        info!("Found screenpad backlight at {:?}", device.sysname());
+                        return Ok(Self {
+                            path: device.syspath().to_path_buf(),
+                            device_type,
+                        });
+                    }
+                }
+            }
+        }
+
+        Err(PlatformError::MissingFunction(format!(
+            "Backlight {:?} not found",
+            device_type
+        )))
+    }
+
+    pub fn device_type(&self) -> &BacklightType {
+        &self.device_type
+    }
+}