[PATCH] leds:lp55xx: Correct Kconfig dependency for f/w user helper

[PATCH] leds:lp55xx: Correct Kconfig dependency for f/w user helper

[Takashi Iwai]

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@vger.kernel.org> # v4.2+
Signed-off-by: Takashi Iwai <tiwai@suse.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.
-- 
2.5.1

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

[Jacek Anaszewski]

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@vger.kernel.org> # v4.2+
> Signed-off-by: Takashi Iwai <tiwai@suse.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.
>


-- 
Best Regards,
Jacek Anaszewski

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

[Kim, Milo]

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@vger.kernel.org> # v4.2+
>> Signed-off-by: Takashi Iwai <tiwai@suse.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

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

[Takashi Iwai]

On Tue, 08 Sep 2015 02:30:07 +0200,
Kim, Milo wrote:
> 
> 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@vger.kernel.org> # v4.2+
> >> Signed-off-by: Takashi Iwai <tiwai@suse.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?

FW_LOADER_USER_HELPER_FALLBACK globally enables the fallback to user
helper mode when no file is loaded by the direct f/w loader.  It
automatically sets FW_LOADER_USER_HELPER.

OTOH, when FW_LOADER_USER_HELPER is set, requeset_firmware_nowait()
does user mode fallback only when uevent (the second) argument is
false.  Note that this is a special case.  In the usual cases --
uevent = true or request_firmware() -- its doesn't enable the
fallback.

The fallback to user helper mode is bad for the recent udev, since
udev already dropped the f/w support code completely.  Thus every
non-existing f/w load will result in 60 seconds stall.

In short, FW_LOAD_USER_HELPER_FALLBACK is present mostly only for
older systems, just for compatibility.  For drivers that need the no
direct f/w load and no udev interaction, set FW_LOAD_USER_HELPER
instead.


Takashi

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

[Jacek Anaszewski]

On 09/08/2015 07:06 AM, Takashi Iwai wrote:
> On Tue, 08 Sep 2015 02:30:07 +0200,
> Kim, Milo wrote:
>>
>> 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@vger.kernel.org> # v4.2+
>>>> Signed-off-by: Takashi Iwai <tiwai@suse.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?
>
> FW_LOADER_USER_HELPER_FALLBACK globally enables the fallback to user
> helper mode when no file is loaded by the direct f/w loader.  It
> automatically sets FW_LOADER_USER_HELPER.
>
> OTOH, when FW_LOADER_USER_HELPER is set, requeset_firmware_nowait()
> does user mode fallback only when uevent (the second) argument is
> false.  Note that this is a special case.  In the usual cases --
> uevent = true or request_firmware() -- its doesn't enable the
> fallback.
>
> The fallback to user helper mode is bad for the recent udev, since
> udev already dropped the f/w support code completely.  Thus every
> non-existing f/w load will result in 60 seconds stall.
>
> In short, FW_LOAD_USER_HELPER_FALLBACK is present mostly only for
> older systems, just for compatibility.  For drivers that need the no
> direct f/w load and no udev interaction, set FW_LOAD_USER_HELPER
> instead.

Merged to fixes-for-4.3 branch of linux-leds.git.
Thanks for this explanation.

-- 
Best Regards,
Jacek Anaszewski

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

[Kim, Milo]

Hi Takashi,

On 9/8/2015 2:06 PM, Takashi Iwai wrote:
> On Tue, 08 Sep 2015 02:30:07 +0200,
> Kim, Milo wrote:
>>
>> 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@vger.kernel.org> # v4.2+
>>>> Signed-off-by: Takashi Iwai <tiwai@suse.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?
>
> FW_LOADER_USER_HELPER_FALLBACK globally enables the fallback to user
> helper mode when no file is loaded by the direct f/w loader.  It
> automatically sets FW_LOADER_USER_HELPER.
>
> OTOH, when FW_LOADER_USER_HELPER is set, requeset_firmware_nowait()
> does user mode fallback only when uevent (the second) argument is
> false.  Note that this is a special case.  In the usual cases --
> uevent = true or request_firmware() -- its doesn't enable the
> fallback.

Yes, I misunderstood here. lp55xx driver needs to enable user mode 
helper as *fallback*, so FW_LOADER_USER_HELPER_FALLBACK was set wrong.
Eventually, it enables the option flag, 'FW_OPT_USERHELPER'. So it 
affects other drivers which call request_firmware().

> The fallback to user helper mode is bad for the recent udev, since
> udev already dropped the f/w support code completely.  Thus every
> non-existing f/w load will result in 60 seconds stall.

However, timeout is changed to MAX_JIFFY_OFFSET when FW_OPT_UEVENT flag 
is not set.

static int _request_firmware_load(struct firmware_priv *fw_priv,
				  unsigned int opt_flags, long timeout)
{
	(snip)

	if (opt_flags & FW_OPT_UEVENT) {
		buf->need_uevent = true;
		dev_set_uevent_suppress(f_dev, false);
		dev_dbg(f_dev, "firmware: requesting %s\n", buf->fw_id);
		kobject_uevent(&fw_priv->dev.kobj, KOBJ_ADD);
	} else {
		timeout = MAX_JIFFY_OFFSET;
	}

	retval = wait_for_completion_interruptible_timeout(&buf->completion,
			timeout);
}

It will take too long to get the result. I don't know the reason why 
timeout was modified in the commit [68ff2a00dbf5: firmware_loader: 
handle timeout via wait_for_completion_interruptible_timeout()].
Moreover, this time value is not identical to the result of 
timeout_show(). Is it OK to remove the line as follows?

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 171841a..8187404 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -909,8 +909,6 @@ static int _request_firmware_load(struct 
firmware_priv *fw_priv,
  		dev_set_uevent_suppress(f_dev, false);
  		dev_dbg(f_dev, "firmware: requesting %s\n", buf->fw_id);
  		kobject_uevent(&fw_priv->dev.kobj, KOBJ_ADD);
-	} else {
-		timeout = MAX_JIFFY_OFFSET;
  	}

  	retval = wait_for_completion_interruptible_timeout(&buf->completion,

If the driver requires longer loading time, then it can be done by 
updating '/sys/class/firmware/timeout'.

> In short, FW_LOAD_USER_HELPER_FALLBACK is present mostly only for
> older systems, just for compatibility.  For drivers that need the no
> direct f/w load and no udev interaction, set FW_LOAD_USER_HELPER
> instead.

Got your point. Thanks for clear explanation.

Best regards,
Milo

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

[Takashi Iwai]

On Tue, 08 Sep 2015 10:25:31 +0200,
Kim, Milo wrote:
> 
> > The fallback to user helper mode is bad for the recent udev, since
> > udev already dropped the f/w support code completely.  Thus every
> > non-existing f/w load will result in 60 seconds stall.
> 
> However, timeout is changed to MAX_JIFFY_OFFSET when FW_OPT_UEVENT flag 
> is not set.
> 
> static int _request_firmware_load(struct firmware_priv *fw_priv,
> 				  unsigned int opt_flags, long timeout)
> {
> 	(snip)
> 
> 	if (opt_flags & FW_OPT_UEVENT) {
> 		buf->need_uevent = true;
> 		dev_set_uevent_suppress(f_dev, false);
> 		dev_dbg(f_dev, "firmware: requesting %s\n", buf->fw_id);
> 		kobject_uevent(&fw_priv->dev.kobj, KOBJ_ADD);
> 	} else {
> 		timeout = MAX_JIFFY_OFFSET;
> 	}
> 
> 	retval = wait_for_completion_interruptible_timeout(&buf->completion,
> 			timeout);
> }
> 
> It will take too long to get the result.

Why it takes too long?  It's the timeout, so it happens only when the
input isn't completed.

> I don't know the reason why 
> timeout was modified in the commit [68ff2a00dbf5: firmware_loader: 
> handle timeout via wait_for_completion_interruptible_timeout()].

My guess about the rationale behind the change is that, if it's no
udev event, the (more-or-less) manual interaction is expected.  If
it's done by human, we can't expect that it's typed always so quickly
in time.

> Moreover, this time value is not identical to the result of 
> timeout_show().

That's bad, indeed.

> Is it OK to remove the line as follows?
> 
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index 171841a..8187404 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -909,8 +909,6 @@ static int _request_firmware_load(struct 
> firmware_priv *fw_priv,
>   		dev_set_uevent_suppress(f_dev, false);
>   		dev_dbg(f_dev, "firmware: requesting %s\n", buf->fw_id);
>   		kobject_uevent(&fw_priv->dev.kobj, KOBJ_ADD);
> -	} else {
> -		timeout = MAX_JIFFY_OFFSET;
>   	}
> 
>   	retval = wait_for_completion_interruptible_timeout(&buf->completion,
> 
> If the driver requires longer loading time, then it can be done by 
> updating '/sys/class/firmware/timeout'.

I guess this would be harmless for most cases.  But it's better to
have a clarification why the shorter timeout is mandatory...


thanks,

Takashi