On Sun, 09 Aug 2015, Richard Weinberger wrote:

Hi!

-next faces some build issues on UML because of unmet direct dependencies.
Mostly due to HAS_IOMEM and I2C.

warning: (MEDIA_SUBDRV_AUTOSELECT && VIDEO_CX231XX && INV_MPU6050_IIO) selects I2C_MUX which has unmet direct dependencies (I2C && HAS_IOMEM)
warning: (ST_IRQCHIP && HIP04_ETH && STMMAC_PLATFORM && DWMAC_IPQ806X && DWMAC_LPC18XX && DWMAC_ROCKCHIP && DWMAC_SOCFPGA && DWMAC_STI && TI_CPSW && PINCTRL_ROCKCHIP &&
PINCTRL_DOVE && POWER_RESET_KEYSTONE && POWER_RESET_SYSCON && POWER_RESET_SYSCON_POWEROFF && S3C2410_WATCHDOG && VIDEO_OMAP3 && VIDEO_S5P_FIMC && RTC_DRV_AT91SAM9 && VIDEO_OMAP4 &&
HWSPINLOCK_QCOM && ATMEL_ST && QCOM_GSBI) selects MFD_SYSCON which has unmet direct dependencies (HAS_IOMEM)
warning: (MEDIA_SUBDRV_AUTOSELECT && VIDEO_CX231XX && INV_MPU6050_IIO) selects I2C_MUX which has unmet direct dependencies (I2C && HAS_IOMEM)
warning: (ST_IRQCHIP && HIP04_ETH && STMMAC_PLATFORM && DWMAC_IPQ806X && DWMAC_LPC18XX && DWMAC_ROCKCHIP && DWMAC_SOCFPGA && DWMAC_STI && TI_CPSW && PINCTRL_ROCKCHIP &&
PINCTRL_DOVE && POWER_RESET_KEYSTONE && POWER_RESET_SYSCON && POWER_RESET_SYSCON_POWEROFF && S3C2410_WATCHDOG && VIDEO_OMAP3 && VIDEO_S5P_FIMC && RTC_DRV_AT91SAM9 && VIDEO_OMAP4 &&
HWSPINLOCK_QCOM && ATMEL_ST && QCOM_GSBI) selects MFD_SYSCON which has unmet direct dependencies (HAS_IOMEM)

For example MFD_SYSCON cannot build on UML as it depends on HAS_IOMEM.
While the symbol MFD_SYSCON has correct dependencies some users of MFD_SYSCON
just issue a "select MFD_SYSCON" and bypass the HAS_IOMEM dependency and causing the build to fail.

This brings me to a question on kconfig itself, wouldn't it be better to just disable a symbol if it has
unmet direct dependencies?

If this is a question about "kconfig itself", you should probably have
included the correct ML and Maintainer:

KCONFIG
M:      Michal Marek [off-list ref]
L:      linux-kbuild-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
S:      Odd Fixes
F:      Documentation/kbuild/kconfig-language.txt
F:      scripts/kconfig/

There are also quite a few interested parties on LKML who might be
inclined to submit a fix for you.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog