linux-kernel - Re: [PATCH] leds:lp55xx: Correct Kconfig dependency for f/w user helper

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Date:	Tue, 8 Sep 2015 09:30:07 +0900
From:	"Kim, Milo" <milo.kim@...com>
To:	Takashi Iwai <tiwai@...e.de>
CC:	Jacek Anaszewski <j.anaszewski@...sung.com>,
	<linux-leds@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Richard Purdie <rpurdie@...ys.net>,
	Bryan Wu <cooloney@...il.com>
Subject: Re: [PATCH] leds:lp55xx: Correct Kconfig dependency for f/w user
 helper

Hi Takashi,

On 9/7/2015 11:19 PM, Jacek Anaszewski wrote:
> Hi Takashi,
>
> Thanks for chasing this.
> Milo, could you express your opinion?
>
> On 09/07/2015 02:25 PM, Takashi Iwai wrote:
>> The commit [b67893206fc0: leds:lp55xx: fix firmware loading error]
>> tries to address the firmware file handling with user helper, but it
>> sets a wrong Kconfig CONFIG_FW_LOADER_USER_HELPER_FALLBACK.  Since the
>> wrong option was enabled, the system got a regression -- it suffers
>> from the unexpected long delays for non-present firmware files.
>>
>> This patch corrects the Kconfig dependency to the right one,
>> CONFIG_FW_LOADER_USER_HELPER.  This doesn't change the fallback
>> behavior but only enables UMH when needed.
>>
>> Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=944661
>> Fixes: b67893206fc0 ('leds:lp55xx: fix firmware loading error')
>> Cc: <stable@...r.kernel.org> # v4.2+
>> Signed-off-by: Takashi Iwai <tiwai@...e.de>
>> ---
>>    drivers/leds/Kconfig | 2 +-
>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>> index 70f4255ff291..2ba52bc2e174 100644
>> --- a/drivers/leds/Kconfig
>> +++ b/drivers/leds/Kconfig
>> @@ -229,7 +229,7 @@ config LEDS_LP55XX_COMMON
>>    	tristate "Common Driver for TI/National LP5521/5523/55231/5562/8501"
>>    	depends on LEDS_LP5521 || LEDS_LP5523 || LEDS_LP5562 || LEDS_LP8501
>>    	select FW_LOADER
>> -	select FW_LOADER_USER_HELPER_FALLBACK
>> +	select FW_LOADER_USER_HELPER
>>    	help
>>    	  This option supports common operations for LP5521/5523/55231/5562/8501
>>    	  devices.

Thank for catching this. It seems I misunderstood firmware helper 
configuration. LP55xx driver uses firmware interface to activate LED 
visual effect. So this driver enables FW_LOADER_USER_HELPER_FALLBACK and 
calls request_firmware_nowait() without uevent. Then, it will try to 
load raw data manually when binary(firmware) file doesn't exist.

I'm still not clear what the difference is between FW_LOADER_USER_HELPER 
and FW_LOADER_USER_HELPER_FALLBACK. Kconfig description makes me confused.
Could you explain it in more details?

Best regards,
Milo
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