From: Arnd Bergmann <arnd@arndb.de>

This driver uses the legacy gpiolib interfaces to get gpio
numbers from platform data:

drivers/mfd/si476x-i2c.c: In function 'si476x_core_start':
   drivers/mfd/si476x-i2c.c:133:21: error: implicit declaration of function 'gpio_is_valid'; did you mean 'uuid_is_valid'? [-Werror=implicit-function-declaration]
     133 |                 if (gpio_is_valid(core->gpio_reset))

There are no in-tree users of this driver, so nothing defines
the platform data.

Add a dependency on GPIOLIB_LEGACY for the moment to avoid the build
failure, and make sure the sound driver does not get built without the
mfd portion either pass that dependency along.

Alternatively, we could remove the mfd driver along with the radio and
sound portions.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202507231653.UFlH2dMO-lkp@intel.com/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/mfd/Kconfig      | 1 +
 sound/soc/codecs/Kconfig | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 425c5fba6cb1..6d52a3d22430 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -1411,6 +1411,7 @@ config MFD_SEC_I2C
 config MFD_SI476X_CORE
 	tristate "Silicon Laboratories 4761/64/68 AM/FM radio."
 	depends on I2C
+	depends on GPIOLIB_LEGACY
 	select MFD_CORE
 	select REGMAP_I2C
 	help
diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
index 759bcb8260cd..9d5b449fa747 100644
--- a/sound/soc/codecs/Kconfig
+++ b/sound/soc/codecs/Kconfig
@@ -1903,6 +1903,7 @@ config SND_SOC_SGTL5000
 
 config SND_SOC_SI476X
 	tristate
+	depends on MFD_SI476X_CORE
 
 config SND_SOC_SIGMADSP
 	tristate
-- 
2.39.5