linux-kernel - Re: [PATCH 1/2] asm-generic/io.h: provide default ioremap/iounmap for !HAS

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Date:	Tue, 29 Mar 2016 15:13:38 -0500
From:	Rob Herring <robh@...nel.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Lee Jones <lee.jones@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Richard Weinberger <richard@....at>,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [PATCH 1/2] asm-generic/io.h: provide default ioremap/iounmap for !HAS_IOMEM

On Tue, Mar 29, 2016 at 2:37 PM, Arnd Bergmann <arnd@...db.de> 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 <fengguang.wu@...el.com>
>> Cc: Arnd Bergmann <arnd@...db.de>
>> Cc: linux-arch@...r.kernel.org
>> Signed-off-by: Rob Herring <robh@...nel.org>
>
> (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.

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.

Rob