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

From: Kim, Milo
Date: Mon Sep 07 2015 - 20:30:38 EST

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.

Fixes: b67893206fc0 ('leds:lp55xx: fix firmware loading error')
Cc: <stable@xxxxxxxxxxxxxxx> # v4.2+
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
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
This option supports common operations for LP5521/5523/55231/5562/8501

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,
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