Re: [PATCH v8 7/7] platform/x86/dell-*: Call led_classdev_notify_brightness_hw_changed on kbd brightness change

[Hans de Goede <hdegoede@xxxxxxxxxx>]

Hi,

On 21-02-17 15:11, Pali Rohár wrote:
> On Thursday 09 February 2017 16:44:17 Hans de Goede wrote:
> > Make dell-wmi notify on hotkey kbd brightness changes, listen for this
> > in dell-laptop and call led_classdev_notify_brightness_hw_changed.
> >
> > This will allow userspace to monitor (poll) for brightness changes on
> > these LEDs caused by the hotkey.
> >
> > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> > Changes in v2:
> > -Use the new dell_smbios*notify functionality
> > Changes in v3:
> > -Simplify the if condition for calling led_notify_brightness_change
> > Changes in v4:
> > -Adjust for dell_smbios_*_notifier to dell_laptop_*_notifier rename
> > Changes in v5:
> > -Switch to new led-trigger based API for notifying userspace about
> >  keyboard backlight brightness changes.
> > Changes in v6:
> > -Switch to new brightness_hw_changed LED class API
> > Changes in v8:
> > -Cache last set brightness value and only call
> >  led_classdev_notify_brightness_hw_changed if the brightness has changed,
> >  this is necessary because the WMI events get triggered when we set the
> >  brightness ourselves too
>
> NAK. This does not work. Brightness can and already is handled also by
> userspace application from Dell libsmbios package. Not every brightness
> change is going via kernel driver and so new variable kbd_led_brightness
> contains just random value.

This shows why it is a bad idea to have userspace code directly poking the
hardware. There is a reason why we've been moving away from the xserver
directly poking gpu-s to doing everything in the kernel.

To me libsmbios is a relic, something of ages long gone by and a normal
user should never use it.

You're right that it can be used to change things underneath the kernel,
but as said normally a user should never do that.

What will happen if a user does that regardless is that an acpi event
will trigger and the following code will execute:

+		mutex_lock(&kbd_led_mutex);
+
+		brightness = kbd_led_level_get(&kbd_led);
+		if (kbd_led_brightness != brightness) {
+			kbd_led_brightness = brightness;
+			led_classdev_notify_brightness_hw_changed(&kbd_led,
+								  brightness);
+		}
+
+		mutex_unlock(&kbd_led_mutex);

After which the kbd_led_brightness will be in sync again, so basically
the only side effect of the user changing the keyboard brightness
through libsmbios will be led_classdev_notify_brightness_hw_changed()
getting called, which is not unsurprising if you change something outside
of the kernel, so I really see no problem here.

Currently the only listener for led_classdev_notify_brightness_hw_changed()
is the gnome3 desktop stack, and having the keyboard brightness
slider in the control panel update when setting the brightness outside
of the normal ways actually is a good thing.

Regards,

Hans

> > ---
> >  drivers/platform/x86/dell-laptop.c | 47 +++++++++++++++++++++++++++++++++++++-
> >  drivers/platform/x86/dell-wmi.c    | 14 ++++++++----
> >  2 files changed, 55 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
> > index 70951f3..f30938b 100644
> > --- a/drivers/platform/x86/dell-laptop.c
> > +++ b/drivers/platform/x86/dell-laptop.c
> > @@ -1133,6 +1133,7 @@ static u8 kbd_previous_level;
> >  static u8 kbd_previous_mode_bit;
> >
> >  static bool kbd_led_present;
> > +static enum led_brightness kbd_led_brightness;
> >  static DEFINE_MUTEX(kbd_led_mutex);
> >
> >  /*
> > @@ -1943,6 +1944,7 @@ static enum led_brightness kbd_led_level_get(struct led_classdev *led_cdev)
> >  static int kbd_led_level_set(struct led_classdev *led_cdev,
> >  			     enum led_brightness value)
> >  {
> > +	enum led_brightness new_brightness = value;
> >  	struct kbd_state state;
> >  	struct kbd_state new_state;
> >  	u16 num;
> > @@ -1971,6 +1973,8 @@ static int kbd_led_level_set(struct led_classdev *led_cdev,
> >  		ret = -ENXIO;
> >  	}
> >
> > +	if (ret == 0)
> > +		kbd_led_brightness = new_brightness;
> >  out:
> >  	mutex_unlock(&kbd_led_mutex);
> >  	return ret;
> > @@ -1978,6 +1982,7 @@ static int kbd_led_level_set(struct led_classdev *led_cdev,
> >
> >  static struct led_classdev kbd_led = {
> >  	.name           = "dell::kbd_backlight",
> > +	.flags		= LED_BRIGHT_HW_CHANGED,
> >  	.brightness_set_blocking = kbd_led_level_set,
> >  	.brightness_get = kbd_led_level_get,
> >  	.groups         = kbd_led_groups,
> > @@ -1985,6 +1990,8 @@ static struct led_classdev kbd_led = {
> >
> >  static int __init kbd_led_init(struct device *dev)
> >  {
> > +	int ret;
> > +
> >  	kbd_init();
> >  	if (!kbd_led_present)
> >  		return -ENODEV;
> > @@ -1996,7 +2003,12 @@ static int __init kbd_led_init(struct device *dev)
> >  		if (kbd_led.max_brightness)
> >  			kbd_led.max_brightness--;
> >  	}
> > -	return led_classdev_register(dev, &kbd_led);
> > +	kbd_led_brightness = kbd_led_level_get(&kbd_led);
> > +	ret = led_classdev_register(dev, &kbd_led);
> > +	if (ret)
> > +		kbd_led_present = false;
> > +
> > +	return ret;
> >  }
> >
> >  static void brightness_set_exit(struct led_classdev *led_cdev,
> > @@ -2013,6 +2025,36 @@ static void kbd_led_exit(void)
> >  	led_classdev_unregister(&kbd_led);
> >  }
> >
> > +static int dell_laptop_notifier_call(struct notifier_block *nb,
> > +				     unsigned long action, void *data)
> > +{
> > +	enum led_brightness brightness;
> > +
> > +	switch (action) {
> > +	case DELL_LAPTOP_KBD_BACKLIGHT_BRIGHTNESS_CHANGED:
> > +		if (!kbd_led_present)
> > +			break;
> > +
> > +		mutex_lock(&kbd_led_mutex);
> > +
> > +		brightness = kbd_led_level_get(&kbd_led);
> > +		if (kbd_led_brightness != brightness) {
> > +			kbd_led_brightness = brightness;
> > +			led_classdev_notify_brightness_hw_changed(&kbd_led,
> > +								  brightness);
> > +		}
> > +
> > +		mutex_unlock(&kbd_led_mutex);
> > +		break;
> > +	}
> > +
> > +	return NOTIFY_OK;
> > +}
> > +
> > +static struct notifier_block dell_laptop_notifier = {
> > +	.notifier_call = dell_laptop_notifier_call,
> > +};
> > +
> >  static int __init dell_init(void)
> >  {
> >  	struct calling_interface_buffer *buffer;
> > @@ -2056,6 +2098,8 @@ static int __init dell_init(void)
> >  		debugfs_create_file("rfkill", 0444, dell_laptop_dir, NULL,
> >  				    &dell_debugfs_fops);
> >
> > +	dell_laptop_register_notifier(&dell_laptop_notifier);
> > +
> >  	if (acpi_video_get_backlight_type() != acpi_backlight_vendor)
> >  		return 0;
> >
> > @@ -2107,6 +2151,7 @@ static int __init dell_init(void)
> >
> >  static void __exit dell_exit(void)
> >  {
> > +	dell_laptop_unregister_notifier(&dell_laptop_notifier);
> >  	debugfs_remove_recursive(dell_laptop_dir);
> >  	if (quirks && quirks->touchpad_led)
> >  		touchpad_led_exit();
> > diff --git a/drivers/platform/x86/dell-wmi.c b/drivers/platform/x86/dell-wmi.c
> > index 75e6370..15740b5 100644
> > --- a/drivers/platform/x86/dell-wmi.c
> > +++ b/drivers/platform/x86/dell-wmi.c
> > @@ -297,11 +297,11 @@ static const struct key_entry dell_wmi_keymap_type_0011[] __initconst = {
> >  	{ KE_IGNORE, 0xfff1, { KEY_RESERVED } },
> >
> >  	/* Keyboard backlight level changed */
> > -	{ KE_IGNORE, 0x01e1, { KEY_RESERVED } },
> > -	{ KE_IGNORE, 0x02ea, { KEY_RESERVED } },
> > -	{ KE_IGNORE, 0x02eb, { KEY_RESERVED } },
> > -	{ KE_IGNORE, 0x02ec, { KEY_RESERVED } },
> > -	{ KE_IGNORE, 0x02f6, { KEY_RESERVED } },
> > +	{ KE_IGNORE, 0x01e1, { KEY_KBDILLUMTOGGLE } },
> > +	{ KE_IGNORE, 0x02ea, { KEY_KBDILLUMTOGGLE } },
> > +	{ KE_IGNORE, 0x02eb, { KEY_KBDILLUMTOGGLE } },
> > +	{ KE_IGNORE, 0x02ec, { KEY_KBDILLUMTOGGLE } },
> > +	{ KE_IGNORE, 0x02f6, { KEY_KBDILLUMTOGGLE } },
> >  };
> >
> >  static struct input_dev *dell_wmi_input_dev;
> > @@ -329,6 +329,10 @@ static void dell_wmi_process_key(int type, int code)
> >  	if (type == 0x0000 && code == 0xe025 && !wmi_requires_smbios_request)
> >  		return;
> >
> > +	if (key->keycode == KEY_KBDILLUMTOGGLE)
> > +		dell_laptop_call_notifier(
> > +			DELL_LAPTOP_KBD_BACKLIGHT_BRIGHTNESS_CHANGED, NULL);
> > +
> >  	sparse_keymap_report_entry(dell_wmi_input_dev, key, 1, true);
> >  }