Re: [RFC PATCH V2] Input: elan_i2c_smbus - resend ENABLE_TP on wake from sleep (NOT TESTED, NEEDS TESTER!) (v2: typo fixes)

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] input: elan_i2c: ENABLE_TP command sent after set_mode() may clobber absolute mode
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commit 37faf4759d30c6532910d41f48a2708415776398
Author: Raphaël Larocque <rlarocque@disroot.org>
Input: elan_i2c_smbus - resend ENABLE_TP on wake from sleep (NOT TESTED, NEEDS TESTER!) (v2: typo fixes)

This commit updates elan_smbus_sleep_control() to resend the
ETP_SMBUS_ENABLE_TP command when waking the controller from sleep.

> diff --git a/drivers/input/mouse/elan_i2c_smbus.c b/drivers/input/mouse/elan_i2c_smbus.c
> index 0287441cda46d..dd86bd1739c55 100644
> --- a/drivers/input/mouse/elan_i2c_smbus.c
> +++ b/drivers/input/mouse/elan_i2c_smbus.c
> @@ -93,10 +93,25 @@ static int elan_smbus_set_mode(struct i2c_client *client, u8 mode)
>  
>  static int elan_smbus_sleep_control(struct i2c_client *client, bool sleep)
>  {
[ ... ]
> +	/*
> +	 * The controller stops touch reporting while asleep; resend
> +	 * ETP_SMBUS_ENABLE_TP on wake, mirroring what is done during
> +	 * elan_smbus_initialize(), so that reporting actually resumes.
> +	 */
> +	error = i2c_smbus_write_byte(client, ETP_SMBUS_ENABLE_TP);

[Severity: Medium]
Could this clobber the absolute mode configuration for non-ASUS devices?

Looking at __elan_initialize() in drivers/input/mouse/elan_i2c_core.c,
non-ASUS devices first configure absolute mode via set_mode(), and then
call sleep_control() to wake the device:

	data->mode |= ETP_ENABLE_ABS;
	error = data->ops->set_mode(client, data->mode);
	if (error) {
		...
	}

	if (!woken_up) {
		error = data->ops->sleep_control(client, false);
		...
	}

Since this patch now sends ETP_SMBUS_ENABLE_TP in sleep_control() on
wake, it gets transmitted after set_mode() for these non-ASUS devices.
Could sending this command after configuring absolute mode reset the
hardware to its default relative mode, breaking absolute touch reporting?

> +	if (error) {
> +		dev_err(&client->dev,
> +			"failed to re-enable touchpad after wake: %d\n",
> +			error);
> +		return error;
> +	}
> +
> +	return 0;
>  }

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Sashiko AI review · https://sashiko.dev/#/patchset/20260922233549.10431-1-rlarocque@disroot.org?part=1