[Bug 214899] ideapad-laptop: platform backlight device not working

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https://bugzilla.kernel.org/show_bug.cgi?id=214899

--- Comment #7 from Hans de Goede (jwrdegoede@xxxxxxxxxxxxxxxxx) ---
The ideapad-laptop code seems to log to dmesg on most unknown events, I assume
nothing shows up in dmesg?

I think based on your other experiments that it would be interesting to log the
value of now in this function in ideapad-laptop.c:


static void ideapad_backlight_notify_brightness(struct ideapad_private *priv)
{
        unsigned long now;

        /* if we control brightness via acpi video driver */
        if (!priv->blightdev)
                read_ec_data(priv->adev->handle, VPCCMD_R_BL, &now);
        else
                backlight_force_update(priv->blightdev,
BACKLIGHT_UPDATE_HOTKEY);
}

Changing it to:

static void ideapad_backlight_notify_brightness(struct ideapad_private *priv)
{
        unsigned long now;

        /* if we control brightness via acpi video driver */
        if (!priv->blightdev) {
                read_ec_data(priv->adev->handle, VPCCMD_R_BL, &now);
                pr_info("EC's LCD backlight value is now: %ld\n", now);
        } else
                backlight_force_update(priv->blightdev,
BACKLIGHT_UPDATE_HOTKEY);
}


I suspect that we will see that value change (note this assumes you do not
specify an acpi_backlight= kernel cmdline option).

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