linux-kernel - Re: [PATCH v12 05/11] edma: config: Enable config options for EDMA

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Message-ID: <CAD=GYpZ_5Lp1La=f+2BQfmuj+sc3FgygZRD4gfj4JGGZ0Do=_Q@mail.gmail.com>
Date:	Fri, 21 Jun 2013 09:20:01 -0500
From:	Joel A Fernandes <agnel.joel@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Sekhar Nori <nsekhar@...com>, Joel A Fernandes <joelagnel@...com>,
	Tony Lindgren <tony@...mide.com>,
	Matt Porter <matt@...orter.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Vinod Koul <vinod.koul@...el.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Benoit Cousson <b-cousson@...com>,
	Russell King <linux@....linux.org.uk>,
	Rob Landley <rob@...dley.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jason Kridner <jkridner@...gleboard.org>,
	Koen Kooi <koen@...gleboard.org>,
	Devicetree Discuss <devicetree-discuss@...ts.ozlabs.org>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Documentation List <linux-doc@...r.kernel.org>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux SPI Devel List 
	<spi-devel-general@...ts.sourceforge.net>
Subject: Re: [PATCH v12 05/11] edma: config: Enable config options for EDMA

On Fri, Jun 21, 2013 at 9:00 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Friday 21 June 2013, Joel A Fernandes wrote:
>> >> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> >> index b1c66a4..7d58cd9 100644
>> >> --- a/arch/arm/Kconfig
>> >> +++ b/arch/arm/Kconfig
>> >> @@ -841,6 +841,7 @@ config ARCH_DAVINCI
>> >>       select HAVE_IDE
>> >>       select NEED_MACH_GPIO_H
>> >>       select TI_PRIV_EDMA
>> >> +     select DMADEVICES
>> >
>> > It is generally a bad idea to force select on something that can be
>> > enabled using menuconfig. Unless used carefully, select causes "unmet
>> > direct dependency" warnings which folks are already fighting hard to
>> > fix. This leads to what Russell referred in the past as "select madness" [1]
>>
>> Are you concerned with bloat issues? I know your point of view but the idea
>> was to build these options by default for these platforms even though
>> in some cases
>> it might not be used. I have seen folks including myself select the wrong
>> option. Having the build system automatically select the correct option for the
>> most common cases can be very useful I feel and not require manual
>> configuration.
>
> For defaults, you should use the defconfig, not 'select' in Kconfig.
>
> A lot of the 'select' statements are actually wrong because they
> do not take dependencies into account where A selects B but not C,
> and B depends on C, which leads to broken builds when C is disabled
> by a user (or randconfig).

I haven't come across this problem but- are you saying there is a
shortcoming in Kbuild/Kconfig that selects an option even if its
dependency is not met?

The problem with defconfig is also too many options I feel for a common case.
CONFIG_DMADEVICES=y
CONFIG_TI_EDMA=y

Most if not all future OMAPs from will use EDMA. Why not we can be
explicit about it and just built it in anyway. If ARCH_OMAP and
DMADEVICES are selected, then we can just build EDMA in by default.

I agree maybe the option can be dropped from Davinci but I suggest
let's keep it for OMAP. Is that ok?

Thanks,
Joel
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