Re: [PATCH v3 1/1] platform/x86: asus-wmi: add support for ASUS screenpad

[Luke Jones <luke@ljones.dev>]

On Tue, 2023-06-20 at 15:00 +1200, 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@ljones.dev>
> ---
>  drivers/platform/x86/asus-wmi.c            | 129
> +++++++++++++++++++++
>  drivers/platform/x86/asus-wmi.h            |   1 +
>  include/linux/platform_data/x86/asus-wmi.h |   4 +
>  3 files changed, 134 insertions(+)
> 
> diff --git a/drivers/platform/x86/asus-wmi.c
> b/drivers/platform/x86/asus-wmi.c
> index 62cee13f5576..c87fbd81d658 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 +3841,124 @@ 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 power, brightness;
> +
> +       power = read_screenpad_backlight_power(asus);
> +       if (power < 0)
> +               return power;
> +
> +       brightness = read_screenpad_brightness(bd);
> +       if (brightness < 0)
> +               return brightness;

I have made a mistake here. If power is off then
read_screenpad_backlight_power() tries to return a stored brightness
from the dev struct but this is uninitialised at this point.

I will submit v4.

> +
> +       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;
> +       /*
> +        * Counter an odd behaviour where default is set to < 13 if
> it was 0 on boot.
> +        * 60 is subjective, but accepted as a good compromise to
> retain visibility.
> +        */
> +       if (brightness < 60)
> +               brightness = 60;
> +
> +       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 +4624,12 @@ 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 +4653,8 @@ 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 +4681,7 @@ 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
>