linux-kernel - Re: [PATCH v2 1/1] platform/x86: asus-wmi: add support for ASUS screenpad

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Date:   Fri, 5 May 2023 18:30:36 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Luke Jones <luke@...nes.dev>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        acpi4asus-user@...ts.sourceforge.net, hdegoede@...hat.com,
        corentin.chary@...il.com, markgross@...nel.org, jdelvare@...e.com
Subject: Re: [PATCH v2 1/1] platform/x86: asus-wmi: add support for ASUS
 screenpad

On 5/5/23 16:43, Luke Jones wrote:
> 
> 
> On Fri, May 5 2023 at 16:08:16 +0300, Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com> wrote:
>> On Fri, 5 May 2023, 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@...nes.dev>
>>>  ---
>>>   .../ABI/testing/sysfs-platform-asus-wmi       |   2 +-
>>>   drivers/platform/x86/asus-wmi.c               | 132 ++++++++++++++++++
>>>   drivers/platform/x86/asus-wmi.h               |   1 +
>>>   include/linux/platform_data/x86/asus-wmi.h    |   4 +
>>>   4 files changed, 138 insertions(+), 1 deletion(-)
>>>
>>>  diff --git a/Documentation/ABI/testing/sysfs-platform-asus-wmi b/Documentation/ABI/testing/sysfs-platform-asus-wmi
>>>  index a77a004a1baa..df9817c6233a 100644
>>>  --- a/Documentation/ABI/testing/sysfs-platform-asus-wmi
>>>  +++ b/Documentation/ABI/testing/sysfs-platform-asus-wmi
>>>  @@ -97,4 +97,4 @@ Contact:    "Luke Jones" <luke@...nes.dev>
>>>   Description:
>>>           Enable an LCD response-time boost to reduce or remove ghosting:
>>>               * 0 - Disable,
>>>  -            * 1 - Enable
>>>  +            * 1 - Enable
>>>  \ No newline at end of file
>>
>> Spurious change?
> 
> Indeed it is. Not sure how that occurred.
> 
>>
>>>  diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
>>>  index 1038dfdcdd32..0528eef02ef7 100644
>>>  --- a/drivers/platform/x86/asus-wmi.c
>>>  +++ b/drivers/platform/x86/asus-wmi.c
>>>  @@ -200,6 +200,7 @@ 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;
>>>  @@ -3208,6 +3209,129 @@ static int is_display_toggle(int code)
>>>       return 0;
>>>   }
>>>
>>>  +/* Screenpad backlight */
>>>  +
>>>  +static int read_screenpad_backlight_power(struct asus_wmi *asus)
>>>  +{
>>>  +    int ret = asus_wmi_get_devstate_simple(asus, ASUS_WMI_DEVID_SCREENPAD_POWER);
>>
>> Please move this to own line because now you have the extra newline
>> in between the call and error handling.
> 
> I don't understand what you mean sorry. Remove the new line or:
> 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 == -ENODEV)
>>>  +        return err;
>>
>> Just return 0. Or is there perhaps something wrong/missing here?
> 
> I thought the correct thing was to return any possible error state (here, anything less than 0 would be an error, right?)
> 

Well, yes, but you are not returning an error. You are returning 'err'
which is 0 at this point. So, at the very least, this code is (very)
misleading since it suggests that it would return some error
(as saved in the 'err' variable) when it doesn't.

Guenter