[PATCH] iio: adc: ad_sigma_delta: allow COMPILE_TEST in isolation

[Radu Sabau via B4 Relay]

From: Radu Sabau <radu.sabau@xxxxxxxxxx>

AD_SIGMA_DELTA is a hidden tristate that can only be enabled by
selecting drivers (AD7124, AD7192, etc.), all of which require SPI.
This prevents compile-testing the library code directly with allmodconfig
or by manually enabling it with COMPILE_TEST.

Add a prompt string guarded by "if COMPILE_TEST" so the symbol becomes
directly selectable when COMPILE_TEST is set.

Also add an explicit "depends on SPI" since the ad_sigma_delta library
directly calls SPI core symbols such as spi_bus_lock(), spi_bus_unlock(),
and spi_sync_locked().

Signed-off-by: Radu Sabau <radu.sabau@xxxxxxxxxx>
---
 drivers/iio/adc/Kconfig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index a9dedbb8eb46..329d1f6e5106 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -33,7 +33,8 @@ config AB8500_GPADC
 	  and USB voltages integral to the U8500 platform.
 
 config AD_SIGMA_DELTA
-	tristate
+	tristate "Analog Devices Sigma-Delta Modulator support" if COMPILE_TEST
+	depends on SPI
 	select IIO_BUFFER
 	select IIO_BUFFER_DMAENGINE
 	select IIO_TRIGGERED_BUFFER

---
base-commit: 4549871118cf616eecdd2d939f78e3b9e1dddc48
change-id: 20260608-ad_sigma_delta_spi-6063f200195b

Best regards,
-- 
Radu Sabau <radu.sabau@xxxxxxxxxx>