[PATCH v2] platform/x86: dell-laptop: Fix bogus keyboard backlight sysfs interface

[PATCH v2] platform/x86: dell-laptop: Fix bogus keyboard backlight sysfs interface

[Kai-Heng Feng]

Dell Latitude 3160 does not have keyboard backlight, but there is a
sysfs interface for it, which does nothing at all.

KBD_LED_ON_TOKEN is the only token can be found. Since it doesn't have
KBD_LED_OFF_TOKEN or KBD_LED_AUTO_*_TOKEN, it should be safe to assume it
does not support keyboard backlight.

Models which do not use SMBIOS to control keyboard backlight, also have
this issue. Brightness level is 0 on these models. Verified on Dell
Inspiron 3565.

Reports keyboard backlight is supported only when tokens other than
KBD_LED_ON_TOKEN can be found, or brightness level is not 0.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---

v2:
The only token can be found is actually KBD_LED_ON_TOKEN, which is BIT(5),
instead of KBD_LED_OFF_TOKEN. Change commit log accordingly.

Use token bit to make the intention more clear.
Also consider kbd_mode_levels_count and kbd_info.levels, suggested by
Pali Rohár.

Use XOR to simplify the bitmask comparison, suggested by
Andy Shevchenko.

 drivers/platform/x86/dell-laptop.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
index ec202094bd50..4b21fc982cb0 100644
--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -1148,6 +1148,15 @@ static const int kbd_tokens[] = {
 	KBD_LED_ON_TOKEN,
 };
 
+enum kbd_led_token_bit {
+	KBD_LED_TOKEN_BIT_OFF = 0,
+	KBD_LED_TOKEN_BIT_AUTO_25,
+	KBD_LED_TOKEN_BIT_AUTO_50,
+	KBD_LED_TOKEN_BIT_AUTO_75,
+	KBD_LED_TOKEN_BIT_AUTO_100,
+	KBD_LED_TOKEN_BIT_ON,
+};
+
 static u16 kbd_token_bits;
 
 static struct kbd_info kbd_info;
@@ -1510,7 +1519,12 @@ static void kbd_init(void)
 	ret = kbd_init_info();
 	kbd_init_tokens();
 
-	if (kbd_token_bits != 0 || ret == 0)
+	/*
+	 * If brightness level is 0, or KBD_LED_ON_TOKEN is the only token,
+	 * consider there is no keyboard backlight.
+	 */
+	if ((ret == 0 && (kbd_info.levels || kbd_mode_levels_count)) ||
+	    kbd_token_bits ^ BIT(KBD_LED_TOKEN_BIT_ON))
 		kbd_led_present = true;
 }
 
-- 
2.13.1

Re: [PATCH v2] platform/x86: dell-laptop: Fix bogus keyboard backlight sysfs interface

[Pali Rohár]

On Monday 19 June 2017 15:36:29 Kai-Heng Feng wrote:
> Dell Latitude 3160 does not have keyboard backlight, but there is a
> sysfs interface for it, which does nothing at all.
> 
> KBD_LED_ON_TOKEN is the only token can be found. Since it doesn't have

*ON* really?

> KBD_LED_OFF_TOKEN or KBD_LED_AUTO_*_TOKEN, it should be safe to assume it
> does not support keyboard backlight.
> 
> Models which do not use SMBIOS to control keyboard backlight, also have
> this issue. Brightness level is 0 on these models. Verified on Dell
> Inspiron 3565.
> 
> Reports keyboard backlight is supported only when tokens other than
> KBD_LED_ON_TOKEN can be found, or brightness level is not 0.
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
> 
> v2:
> The only token can be found is actually KBD_LED_ON_TOKEN, which is BIT(5),
> instead of KBD_LED_OFF_TOKEN. Change commit log accordingly.
> 
> Use token bit to make the intention more clear.
> Also consider kbd_mode_levels_count and kbd_info.levels, suggested by
> Pali Rohár.
> 
> Use XOR to simplify the bitmask comparison, suggested by
> Andy Shevchenko.
> 
>  drivers/platform/x86/dell-laptop.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
> index ec202094bd50..4b21fc982cb0 100644
> --- a/drivers/platform/x86/dell-laptop.c
> +++ b/drivers/platform/x86/dell-laptop.c
> @@ -1148,6 +1148,15 @@ static const int kbd_tokens[] = {
>  	KBD_LED_ON_TOKEN,
>  };
>  
> +enum kbd_led_token_bit {
> +	KBD_LED_TOKEN_BIT_OFF = 0,
> +	KBD_LED_TOKEN_BIT_AUTO_25,
> +	KBD_LED_TOKEN_BIT_AUTO_50,
> +	KBD_LED_TOKEN_BIT_AUTO_75,
> +	KBD_LED_TOKEN_BIT_AUTO_100,
> +	KBD_LED_TOKEN_BIT_ON,
> +};
> +
>  static u16 kbd_token_bits;
>  
>  static struct kbd_info kbd_info;
> @@ -1510,7 +1519,12 @@ static void kbd_init(void)
>  	ret = kbd_init_info();
>  	kbd_init_tokens();
>  
> -	if (kbd_token_bits != 0 || ret == 0)
> +	/*
> +	 * If brightness level is 0, or KBD_LED_ON_TOKEN is the only token,
> +	 * consider there is no keyboard backlight.
> +	 */
> +	if ((ret == 0 && (kbd_info.levels || kbd_mode_levels_count)) ||
> +	    kbd_token_bits ^ BIT(KBD_LED_TOKEN_BIT_ON))

So in case there would be only *OFF* token then interface is exported
too... This does not seems to be good idea.

If there is machine for which firmware provides only *ON* token, then I
think we should presence for at least two tokens.

And similarly kbd_mode_levels_count needs to be checked that is at least
two (as "off" is in count).

>  		kbd_led_present = true;
>  }
>  

-- 
Pali Rohár
pali.rohar@gmail.com

Re: [PATCH v2] platform/x86: dell-laptop: Fix bogus keyboard backlight sysfs interface

[Kai-Heng Feng]

On Mon, Jun 19, 2017 at 3:57 PM, Pali Rohár <pali.rohar@gmail.com> wrote:
> On Monday 19 June 2017 15:36:29 Kai-Heng Feng wrote:
>> Dell Latitude 3160 does not have keyboard backlight, but there is a
>> sysfs interface for it, which does nothing at all.
>>
>> KBD_LED_ON_TOKEN is the only token can be found. Since it doesn't have
>
> *ON* really?
>
>> KBD_LED_OFF_TOKEN or KBD_LED_AUTO_*_TOKEN, it should be safe to assume it
>> does not support keyboard backlight.
>>
>> Models which do not use SMBIOS to control keyboard backlight, also have
>> this issue. Brightness level is 0 on these models. Verified on Dell
>> Inspiron 3565.
>>
>> Reports keyboard backlight is supported only when tokens other than
>> KBD_LED_ON_TOKEN can be found, or brightness level is not 0.
>>
>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
>> ---
>>
>> v2:
>> The only token can be found is actually KBD_LED_ON_TOKEN, which is BIT(5),
>> instead of KBD_LED_OFF_TOKEN. Change commit log accordingly.
>>
>> Use token bit to make the intention more clear.
>> Also consider kbd_mode_levels_count and kbd_info.levels, suggested by
>> Pali Rohár.
>>
>> Use XOR to simplify the bitmask comparison, suggested by
>> Andy Shevchenko.
>>
>>  drivers/platform/x86/dell-laptop.c | 16 +++++++++++++++-
>>  1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
>> index ec202094bd50..4b21fc982cb0 100644
>> --- a/drivers/platform/x86/dell-laptop.c
>> +++ b/drivers/platform/x86/dell-laptop.c
>> @@ -1148,6 +1148,15 @@ static const int kbd_tokens[] = {
>>       KBD_LED_ON_TOKEN,
>>  };
>>
>> +enum kbd_led_token_bit {
>> +     KBD_LED_TOKEN_BIT_OFF = 0,
>> +     KBD_LED_TOKEN_BIT_AUTO_25,
>> +     KBD_LED_TOKEN_BIT_AUTO_50,
>> +     KBD_LED_TOKEN_BIT_AUTO_75,
>> +     KBD_LED_TOKEN_BIT_AUTO_100,
>> +     KBD_LED_TOKEN_BIT_ON,
>> +};
>> +
>>  static u16 kbd_token_bits;
>>
>>  static struct kbd_info kbd_info;
>> @@ -1510,7 +1519,12 @@ static void kbd_init(void)
>>       ret = kbd_init_info();
>>       kbd_init_tokens();
>>
>> -     if (kbd_token_bits != 0 || ret == 0)
>> +     /*
>> +      * If brightness level is 0, or KBD_LED_ON_TOKEN is the only token,
>> +      * consider there is no keyboard backlight.
>> +      */
>> +     if ((ret == 0 && (kbd_info.levels || kbd_mode_levels_count)) ||
>> +         kbd_token_bits ^ BIT(KBD_LED_TOKEN_BIT_ON))
>
> So in case there would be only *OFF* token then interface is exported
> too... This does not seems to be good idea.
>
> If there is machine for which firmware provides only *ON* token, then I
> think we should presence for at least two tokens.

So I can use kbd_get_valid_token_counts() >= 2 here.

>
> And similarly kbd_mode_levels_count needs to be checked that is at least
> two (as "off" is in count).

So it should be kbd_mode_levels_count >= 2.
The same rule should also apply to kbd_info.levels, right?

>
>>               kbd_led_present = true;
>>  }
>>
>
> --
> Pali Rohár
> pali.rohar@gmail.com

Re: [PATCH v2] platform/x86: dell-laptop: Fix bogus keyboard backlight sysfs interface

[Pali Rohár]

On Monday 19 June 2017 16:39:14 Kai-Heng Feng wrote:
> The same rule should also apply to kbd_info.levels, right?

IIRC no. levels = 1 means you can set two levels (0 and 1). Look into code.

-- 
Pali Rohár
pali.rohar@gmail.com