Re: [PATCH v4 1/1] platform/x86: asus-wmi: add support for ASUS screenpad

[Hans de Goede]

Hi Luke,

On 6/30/23 06:17, Luke D. Jones wrote:
> Add support for the WMI methods used to turn off and adjust the
> brightness of the secondary "screenpad" device found on some high-end
> ASUS laptops like the GX650P series and others.
> 
> These methods are utilised in a new backlight device named asus_screenpad.
> 
> Signed-off-by: Luke D. Jones <luke@xxxxxxxxxx>

Thank you for your work on this. I have one small change request
and then v5 should be ready for merging, see me inline comment
below.

> ---
>  drivers/platform/x86/asus-wmi.c            | 128 +++++++++++++++++++++
>  drivers/platform/x86/asus-wmi.h            |   1 +
>  include/linux/platform_data/x86/asus-wmi.h |   4 +
>  3 files changed, 133 insertions(+)
> 
> diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
> index 62cee13f5576..967c92ceb041 100644
> --- a/drivers/platform/x86/asus-wmi.c
> +++ b/drivers/platform/x86/asus-wmi.c
> @@ -25,6 +25,7 @@
>  #include <linux/input/sparse-keymap.h>
>  #include <linux/kernel.h>
>  #include <linux/leds.h>
> +#include <linux/minmax.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
>  #include <linux/pci_hotplug.h>
> @@ -212,6 +213,7 @@ struct asus_wmi {
>  
>  	struct input_dev *inputdev;
>  	struct backlight_device *backlight_device;
> +	struct backlight_device *screenpad_backlight_device;
>  	struct platform_device *platform_device;
>  
>  	struct led_classdev wlan_led;
> @@ -3839,6 +3841,123 @@ static int is_display_toggle(int code)
>  	return 0;
>  }
>  
> +/* Screenpad backlight *******************************************************/
> +
> +static int read_screenpad_backlight_power(struct asus_wmi *asus)
> +{
> +	int ret;
> +
> +	ret = asus_wmi_get_devstate_simple(asus, ASUS_WMI_DEVID_SCREENPAD_POWER);
> +	if (ret < 0)
> +		return ret;
> +	/* 1 == powered */
> +	return ret ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
> +}
> +
> +static int read_screenpad_brightness(struct backlight_device *bd)
> +{
> +	struct asus_wmi *asus = bl_get_data(bd);
> +	u32 retval;
> +	int err;
> +
> +	err = read_screenpad_backlight_power(asus);
> +	if (err < 0)
> +		return err;
> +	/* The device brightness can only be read if powered, so return stored */
> +	if (err == FB_BLANK_POWERDOWN)
> +		return asus->driver->screenpad_brightness;
> +
> +	err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_SCREENPAD_LIGHT, &retval);
> +	if (err < 0)
> +		return err;
> +
> +	return retval & ASUS_WMI_DSTS_BRIGHTNESS_MASK;
> +}
> +
> +static int update_screenpad_bl_status(struct backlight_device *bd)
> +{
> +	struct asus_wmi *asus = bl_get_data(bd);
> +	int power, err = 0;
> +	u32 ctrl_param;
> +
> +	power = read_screenpad_backlight_power(asus);
> +	if (power < 0)
> +		return power;
> +
> +	if (bd->props.power != power) {
> +		if (power != FB_BLANK_UNBLANK) {
> +			/* Only brightness > 0 can power it back on */
> +			ctrl_param = max(1, asus->driver->screenpad_brightness);
> +			err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_LIGHT,
> +						    ctrl_param, NULL);
> +		} else {
> +			err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_POWER, 0, NULL);
> +		}
> +	} else if (power == FB_BLANK_UNBLANK) {
> +		/* Only set brightness if powered on or we get invalid/unsync state */
> +		ctrl_param = bd->props.brightness;
> +		err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_LIGHT, ctrl_param, NULL);
> +	}
> +
> +	/* Ensure brightness is stored to turn back on with */
> +	asus->driver->screenpad_brightness = bd->props.brightness;
> +
> +	return err;
> +}
> +
> +static const struct backlight_ops asus_screenpad_bl_ops = {
> +	.get_brightness = read_screenpad_brightness,
> +	.update_status = update_screenpad_bl_status,
> +	.options = BL_CORE_SUSPENDRESUME,
> +};
> +
> +static int asus_screenpad_init(struct asus_wmi *asus)
> +{
> +	struct backlight_device *bd;
> +	struct backlight_properties props;
> +	int err, power;
> +	int brightness = 0;
> +
> +	power = read_screenpad_backlight_power(asus);
> +	if (power < 0)
> +		return power;
> +
> +	if (power != FB_BLANK_POWERDOWN) {
> +		err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_SCREENPAD_LIGHT, &brightness);
> +		if (err < 0)
> +			return err;
> +	}
> +	/* default to an acceptable min brightness on boot if too low */
> +	if (brightness < 60)
> +		brightness = 60;

If settings below 60 are no good, then the correct way to handle
this is to limit the range to 0 - (255-60) and add / substract
60 when setting / getting the brightness.

E.g. do something like this:

#define SCREENPAD_MIN_BRIGHTNESS	60
#define SCREENPAD_MAX_BRIGHTNESS	255

	props.max_brightness = SCREENPAD_MAX_BRIGHTNESS - SCREENPAD_MIN_BRIGHTNESS;

And in update_screenpad_bl_status() do:

	ctrl_param = bd->props.brightness + SCREENPAD_MIN_BRIGHTNESS;

And when reading the brightness substract SCREENPAD_MIN_BRIGHTNESS,
clamping to a minimum value of 0.

This avoids a dead-zone in the brightness range between 0-60 .

Regards,

Hans






> +
> +	memset(&props, 0, sizeof(struct backlight_properties));
> +	props.type = BACKLIGHT_RAW; /* ensure this bd is last to be picked */
> +	props.max_brightness = 255;
> +	bd = backlight_device_register("asus_screenpad",
> +				       &asus->platform_device->dev, asus,
> +				       &asus_screenpad_bl_ops, &props);
> +	if (IS_ERR(bd)) {
> +		pr_err("Could not register backlight device\n");
> +		return PTR_ERR(bd);
> +	}
> +
> +	asus->screenpad_backlight_device = bd;
> +	asus->driver->screenpad_brightness = brightness;
> +	bd->props.brightness = brightness;
> +	bd->props.power = power;
> +	backlight_update_status(bd);
> +
> +	return 0;
> +}
> +
> +static void asus_screenpad_exit(struct asus_wmi *asus)
> +{
> +	backlight_device_unregister(asus->screenpad_backlight_device);
> +
> +	asus->screenpad_backlight_device = NULL;
> +}
> +
>  /* Fn-lock ********************************************************************/
>  
>  static bool asus_wmi_has_fnlock_key(struct asus_wmi *asus)
> @@ -4504,6 +4623,12 @@ static int asus_wmi_add(struct platform_device *pdev)
>  	} else if (asus->driver->quirks->wmi_backlight_set_devstate)
>  		err = asus_wmi_set_devstate(ASUS_WMI_DEVID_BACKLIGHT, 2, NULL);
>  
> +	if (asus_wmi_dev_is_present(asus, ASUS_WMI_DEVID_SCREENPAD_LIGHT)) {
> +		err = asus_screenpad_init(asus);
> +		if (err && err != -ENODEV)
> +			goto fail_screenpad;
> +	}
> +
>  	if (asus_wmi_has_fnlock_key(asus)) {
>  		asus->fnlock_locked = fnlock_default;
>  		asus_wmi_fnlock_update(asus);
> @@ -4527,6 +4652,8 @@ static int asus_wmi_add(struct platform_device *pdev)
>  	asus_wmi_backlight_exit(asus);
>  fail_backlight:
>  	asus_wmi_rfkill_exit(asus);
> +fail_screenpad:
> +	asus_screenpad_exit(asus);
>  fail_rfkill:
>  	asus_wmi_led_exit(asus);
>  fail_leds:
> @@ -4553,6 +4680,7 @@ static int asus_wmi_remove(struct platform_device *device)
>  	asus = platform_get_drvdata(device);
>  	wmi_remove_notify_handler(asus->driver->event_guid);
>  	asus_wmi_backlight_exit(asus);
> +	asus_screenpad_exit(asus);
>  	asus_wmi_input_exit(asus);
>  	asus_wmi_led_exit(asus);
>  	asus_wmi_rfkill_exit(asus);
> diff --git a/drivers/platform/x86/asus-wmi.h b/drivers/platform/x86/asus-wmi.h
> index a478ebfd34df..5fbdd0eafa02 100644
> --- a/drivers/platform/x86/asus-wmi.h
> +++ b/drivers/platform/x86/asus-wmi.h
> @@ -57,6 +57,7 @@ struct quirk_entry {
>  struct asus_wmi_driver {
>  	int			brightness;
>  	int			panel_power;
> +	int			screenpad_brightness;
>  	int			wlan_ctrl_by_user;
>  
>  	const char		*name;
> diff --git a/include/linux/platform_data/x86/asus-wmi.h b/include/linux/platform_data/x86/asus-wmi.h
> index d17ae2eb0f8d..61ba70b32846 100644
> --- a/include/linux/platform_data/x86/asus-wmi.h
> +++ b/include/linux/platform_data/x86/asus-wmi.h
> @@ -58,6 +58,10 @@
>  #define ASUS_WMI_DEVID_KBD_BACKLIGHT	0x00050021
>  #define ASUS_WMI_DEVID_LIGHT_SENSOR	0x00050022 /* ?? */
>  #define ASUS_WMI_DEVID_LIGHTBAR		0x00050025
> +/* This can only be used to disable the screen, not re-enable */
> +#define ASUS_WMI_DEVID_SCREENPAD_POWER	0x00050031
> +/* Writing a brightness re-enables the screen if disabled */
> +#define ASUS_WMI_DEVID_SCREENPAD_LIGHT	0x00050032
>  #define ASUS_WMI_DEVID_FAN_BOOST_MODE	0x00110018
>  #define ASUS_WMI_DEVID_THROTTLE_THERMAL_POLICY 0x00120075
>