--kblight: Fix on some early systems

[JohnAZoidberg]

Tested on:

• Framework Laptop 13 Intel 13th Gen (previously not working)
• Framework Laptop 13 AMD Ryzen AI 300 (previously working)

[Copilot]

Pull request overview

Fixes --kblight on certain early Framework systems by detecting whether the EC supports PwmType::KbLight and falling back to an alternative PWM mapping when it does not.

Changes:

• Added a capability probe (has_pwmtype_kblight()) based on PwmGetDuty.
• Updated set_keyboard_backlight() to fall back to PwmType::Generic with a different index when KbLight isn’t supported.
• Updated get_keyboard_backlight() to use the same fallback logic.

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[Copilot]

Pull request overview

Improves keyboard backlight support on early Framework systems whose EC firmware doesn’t expose the dedicated CONFIG_PWM_KBLIGHT channel by falling back to a generic PWM channel.

Changes:

• Add fallback in set_keyboard_backlight() to use PwmType::Generic index 1 when PwmType::KbLight returns InvalidParameter.
• Add corresponding fallback in get_keyboard_backlight() for the same early-system behavior.
• Refactor shared duty calculation into a local duty variable.

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[Copilot]

res is moved into the if let Err(...) = res pattern match, but then it’s used again afterwards in debug_assert!(res.is_ok()). This won’t compile because EcResult<()> isn’t Copy. Match on &res (or restructure with match res { ... }) so you can both detect InvalidParameter and still use/inspect the original result.

[JohnAZoidberg]

it definitely does compile

[Copilot]

res is moved into if let Err(...) = res, but the else branch then tries to use res?. This won’t compile due to use-after-move. Consider rewriting as a match res { Err(EcError::Response(InvalidParameter)) => { ... }, other => other? } or pattern match on &res and then handle the owned res separately.

Suggested change

	let kblight = if let Err(EcError::Response(EcResponseStatus::InvalidParameter)) = res {
	EcRequestPwmGetDuty {
	pwm_type: PwmType::Generic as u8,
	index: 1,
	}
	.send_command(self)?
	} else {
	res?
	let kblight = match res {
	Err(EcError::Response(EcResponseStatus::InvalidParameter)) => {
	EcRequestPwmGetDuty {
	pwm_type: PwmType::Generic as u8,
	index: 1,
	}
	.send_command(self)?
	}
	other => other?,

[Copilot]

duty is computed with percent as u16 * (PWM_MAX_DUTY / 100), which (a) truncates such that percent == 100 does not reach PWM_MAX_DUTY (0xFFFF), and (b) can wrap on overflow in release builds if a caller passes percent > 100 (the current debug_assert! won’t protect release builds). Compute in a wider integer type (e.g., u32) and clamp/validate percent before converting back to u16.

Suggested change

	let duty = percent as u16 * (PWM_MAX_DUTY / 100);
	let clamped_percent = u32::from(percent).min(100);
	let duty = ((clamped_percent * u32::from(PWM_MAX_DUTY)) / 100) as u16;