Hi Rob,
On Tue, Mar 29, 2016 at 10:13 PM, Rob Herring <[email protected]> wrote:
> On Tue, Mar 29, 2016 at 2:37 PM, Arnd Bergmann <[email protected]> wrote:
>> On Tuesday 29 March 2016 13:23:00 Rob Herring wrote:
>>> Drivers shouldn't have to care about HAS_IOMEM to compile and having to
>>> causes a Kconfig mess:
>>>
>>> warning: (MEDIA_SUBDRV_AUTOSELECT && VIDEO_CX231XX && INV_MPU6050_I2C)
>>> selects I2C_MUX which has unmet direct dependencies (I2C && HAS_IOMEM)
>>> warning: (ST_IRQCHIP && STMMAC_PLATFORM && DWMAC_IPQ806X && DWMAC_LPC18XX
>>> && DWMAC_ROCKCHIP && DWMAC_SOCFPGA && DWMAC_STI && TI_CPSW &&
>>> PINCTRL_ROCKCHIP && PINCTRL_DOVE && POWER_RESET_KEYSTONE &&
>>> S3C2410_WATCHDOG && VIDEO_OMAP3 && VIDEO_S5P_FIMC && USB_XHCI_MTK &&
>>> RTC_DRV_AT91SAM9 && LPC18XX_DMAMUX && VIDEO_OMAP4 && HWSPINLOCK_QCOM &&
>>> ATMEL_ST && QCOM_GSBI && PHY_HI6220_USB) selects MFD_SYSCON which has unmet
>>> direct dependencies (HAS_IOMEM)
>>>
>>> Reuse the !MMU variants for !HAS_IOMEM as they are sufficient for our
>>> needs. This fixes build errors for UM allyesconfig:
>>>
>>> drivers/mfd/syscon.c:89:2: error: implicit declaration of function
>>> 'iounmap' [-Werror=implicit-function-declaration]
>>> iounmap(base);
>>>
>>> Reported-by: Fengguang Wu <[email protected]>
>>> Cc: Arnd Bergmann <[email protected]>
>>> Cc: [email protected]
>>> Signed-off-by: Rob Herring <[email protected]>
>>
>> (adding Richard and the UML list to cc)
>>
>> I actually prototyped a patch that did the opposite: remove the
>> readl/writel/...
>> definitions when HAS_IOMEM is unset. I didn't get far enough to submit it,
>> but see below for what I did.
>
> Ewww. Why do the opposite of what we do for every other Kconfig symbol
> which is provide empty functions? It really only functions as a
> disable on UML flag which runs counter to enabling drivers to build
> for all arches.
Usually the empty function fall into one of two classes:
1. They return an error, so drivers will abort their initialization,
2. They are a plain no-op, for functions with harmless side-effects.
The !MMU versions are not dummies, but assume a transparent translation.
This may lead to drivers continuing their initialization and crashing the
system.
> I actually started a patch to remove the HAS_IOMEM dependency
> everywhere (or just the per driver cases). It didn't break as bad as I
> expected, but became more than I wanted to fix. Mainly, all the devm_
> variants also need empty versions or to be always enabled.
Should these dependencies on HAS_IOMEM be changed to "HAS_IOMEM ||
COMPILE_TEST"?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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