linux-kernel - Re: [PATCH v2 07/11] input: macsmc-hid: New driver to handle the Apple Mac SMC buttons/lid

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Message-ID: <qffp7kadq3xojla5k6f5pr37irgytqfsqvabr6ydvulxnkcgnn@bv5mrraxrhhe>
Date: Fri, 29 Aug 2025 11:11:22 +0000
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: James Calligeros <jcalligeros99@...il.com>
Cc: Sven Peter <sven@...nel.org>, Janne Grunau <j@...nau.net>, 
	Alyssa Rosenzweig <alyssa@...enzweig.io>, Neal Gompa <neal@...pa.dev>, Lee Jones <lee@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Alexandre Belloni <alexandre.belloni@...tlin.com>, 
	Jean Delvare <jdelvare@...e.com>, Guenter Roeck <linux@...ck-us.net>, asahi@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-rtc@...r.kernel.org, linux-hwmon@...r.kernel.org, linux-input@...r.kernel.org, 
	Hector Martin <marcan@...can.st>
Subject: Re: [PATCH v2 07/11] input: macsmc-hid: New driver to handle the
 Apple Mac SMC buttons/lid

Hi James,

On Wed, Aug 27, 2025 at 09:22:41PM +1000, James Calligeros wrote:
> +static void macsmc_hid_event_button(struct macsmc_hid *smchid, unsigned long event)
> +{
> +	u8 button = (event >> 8) & 0xff;
> +	u8 state = !!(event & 0xff);
> +
> +	switch (button) {
> +	case BTN_POWER:
> +	case BTN_TOUCHID:
> +		if (smchid->wakeup_mode) {
> +			if (state)
> +				pm_wakeup_hard_event(smchid->dev);
> +		} else {
> +			input_report_key(smchid->input, KEY_POWER, state);
> +			input_sync(smchid->input);
> +		}

I believe you should be using pm_wakeup_event() in all cases so that
pressing power would interrupt suspend even if resume() handler has not
been run yet. Also I do not think suppressing KEY_POWER is needed.
Userspace should be smart and decide whether to shutdown the system or
not when receiving KEY_POWER depending on the overall system state.

...
> +
> +static int macsmc_hid_probe(struct platform_device *pdev)
> +{
> +	struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
> +	struct macsmc_hid *smchid;
> +	bool have_lid, have_power;
> +	int ret;

	int error;

> +
> +	/* Bail early if this SMC neither supports power button nor lid events */
> +	have_lid = apple_smc_key_exists(smc, SMC_KEY(MSLD));
> +	have_power = apple_smc_key_exists(smc, SMC_KEY(bHLD));
> +	if (!have_lid && !have_power)
> +		return -ENODEV;
> +
> +	smchid = devm_kzalloc(&pdev->dev, sizeof(*smchid), GFP_KERNEL);
> +	if (!smchid)
> +		return -ENOMEM;
> +
> +	smchid->dev = &pdev->dev;
> +	smchid->smc = smc;
> +	platform_set_drvdata(pdev, smchid);
> +
> +	smchid->input = devm_input_allocate_device(&pdev->dev);
> +	if (!smchid->input)
> +		return -ENOMEM;
> +
> +	smchid->input->phys = "macsmc-hid (0)";
> +	smchid->input->name = "Apple SMC power/lid events";
> +
> +	if (have_lid)
> +		input_set_capability(smchid->input, EV_SW, SW_LID);
> +	if (have_power)
> +		input_set_capability(smchid->input, EV_KEY, KEY_POWER);
> +
> +	ret = input_register_device(smchid->input);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to register input device: %d\n", ret);
> +		return ret;
> +	}
> +
> +	if (have_lid) {
> +		u8 val;
> +
> +		ret = apple_smc_read_u8(smc, SMC_KEY(MSLD), &val);
> +		if (ret < 0)
> +			dev_warn(&pdev->dev, "Failed to read initial lid state\n");
> +		else
> +			input_report_switch(smchid->input, SW_LID, val);
> +	}
> +
> +	if (have_power) {
> +		u32 val;
> +
> +		ret = apple_smc_read_u32(smc, SMC_KEY(bHLD), &val);
> +		if (ret < 0)
> +			dev_warn(&pdev->dev, "Failed to read initial power button state\n");
> +		else
> +			input_report_key(smchid->input, KEY_POWER, val & 1);
> +	}

Since you are doing this to seed initial switch/button state I would do
this before registering input device (this is safe to do so).

Thanks.

-- 
Dmitry