--kblight: Fix on some early systems

I tested on Laptop 13 Intel 13th gen and kblight didn't work.

Signed-off-by: Daniel Schaefer <dhs@frame.work>

Author: quinchou77

framework_lib/src/chromium_ec/mod.rs

@@ -770,22 +770,49 @@ impl CrosEc {
     /// * `percent` - An integer from 0 to 100. 0 being off, 100 being full brightness
     pub fn set_keyboard_backlight(&self, percent: u8) {
         debug_assert!(percent <= 100);
+        let duty = percent as u16 * (PWM_MAX_DUTY / 100);
+
         let res = EcRequestPwmSetDuty {
-            duty: percent as u16 * (PWM_MAX_DUTY / 100),
+            duty,
             pwm_type: PwmType::KbLight as u8,
             index: 0,
         }
         .send_command(self);
+
+        // Early systems (hx20/hx30) don't enable CONFIG_PWM_KBLIGHT in their EC firmware;
+        // keyboard backlight is at generic PWM channel index 1.
+        if let Err(EcError::Response(EcResponseStatus::InvalidParameter)) = res {
+            let res = EcRequestPwmSetDuty {
+                duty,
+                pwm_type: PwmType::Generic as u8,
+                index: 1,
+            }
+            .send_command(self);
+            debug_assert!(res.is_ok());
+            return;
+        }
         debug_assert!(res.is_ok());
     }
 
     /// Check the current brightness of the keyboard backlight
     pub fn get_keyboard_backlight(&self) -> EcResult<u8> {
-        let kblight = EcRequestPwmGetDuty {
+        let res = EcRequestPwmGetDuty {
             pwm_type: PwmType::KbLight as u8,
             index: 0,
         }
-        .send_command(self)?;
+        .send_command(self);
+
+        // Early systems (hx20/hx30) don't enable CONFIG_PWM_KBLIGHT in their EC firmware;
+        // keyboard backlight is at generic PWM channel index 1.
+        let kblight = if let Err(EcError::Response(EcResponseStatus::InvalidParameter)) = res {
+            EcRequestPwmGetDuty {
+                pwm_type: PwmType::Generic as u8,
+                index: 1,
+            }
+            .send_command(self)?
+        } else {
+            res?
+        };
 
         Ok((kblight.duty / (PWM_MAX_DUTY / 100)) as u8)
     }