linux-kernel - Re: [PATCH 1/1] irqchip: gpcv2: make config option visible

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Date:   Tue, 22 Jan 2019 11:40:17 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Aisheng Dong <aisheng.dong@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        dl-linux-imx <linux-imx@....com>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Andrey Smirnov <andrew.smirnov@...il.com>
Subject: Re: [PATCH 1/1] irqchip: gpcv2: make config option visible

On Tue, 22 Jan 2019 11:04:48 +0000,
Aisheng Dong <aisheng.dong@....com> wrote:
> 
> 
> 
> > From: Marc Zyngier [mailto:marc.zyngier@....com]
> > Sent: Friday, January 18, 2019 6:10 PM
> [...]
> > >>>
> > >>>  config IMX_GPCV2
> > >>> -	bool
> > >>> +	bool "i.MX GPCv2 IRQ chip"
> > >>> +	depends on ARCH_MXC || (COMPILE_TEST && OF)
> > >>>  	select IRQ_DOMAIN
> > >>>  	help
> > >>>  	  Enables the wakeup IRQs for IMX platforms with GPCv2 block
> > >>>
> > >>
> > >> How does it help exactly? It is pretty difficult for a user to know
> > >> exactly what they need. I'd rather see it selected by ARCH_MXC, which
> > >> makes it
> > >
> > > ARM64 SoC maintainers suggest not add more driver specific options
> > > except an Generic ARCH option.
> > >
> > > As GPCv2 is also used in MX8MQ. So we may select it in armv8 defconfig.
> > > If this option is invisible, we can't select it.
> > 
> > And conversely, users have no idea of what letter soup they have to select to
> > make their HW work properly. Selecting the driver when the platform is
> > supposed to be supported is the right way to solve this problem.
> > 
> 
> I think the problem is that we have no platform specific CONFIGs for arm v8 platforms.
> We have only one CONFIG_ARCH_MXC for all MX8 SoCs, e.g. mx8qxp, mx8mq...
> Only MX8MQ needs to use GPCv2. Selecting GPCv2 under ARCH_MXC means users
> have no chance to disable it for mx8qxp which does not need it.

And where is the problem to select this on platforms that do not
strictly require it? Code bloat?

If you want fine grained selection for people dealing with a single
SoC, make it depend on CONFIG_EXPERT. Don't force this on unsuspecting
users who expect their HW to just work.

Something like:

config IMX_GPCV2
       	bool "i.MX GPCv2 IRQ chip" if EXPERT
	def_bool ARCH_MXC
	select IRQ_DOMAIN
	help
	  Enables the wakeup IRQs for IMX platforms with GPCv2 block

> 
> We probably could introduce SOC option under drivers/soc/ to do the default configs
> selection. But we've already handled all other driver selections in defconfig
> e.g. firmware, clk, pinctrl, power domain and etc.
> Not sure whether GPCv2 should be an exception.

I think something like the above should be the rule. Configuration
feature creep is not helping anyone.

	M.

-- 
Jazz is not dead, it just smell funny.