Message-ID: <20190306124221.bf6qj6zx6jbdcsey@shell.armlinux.org.uk>
Date:   Wed, 6 Mar 2019 12:42:21 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Peng Hao <peng.hao2@....com.cn>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Lucas Stach <l.stach@...gutronix.de>
Subject: Re: Smarter Kconfig help

On Wed, Mar 06, 2019 at 11:34:36AM +0000, Russell King - ARM Linux admin wrote:
> On Wed, Mar 06, 2019 at 12:49:40PM +0200, Andy Shevchenko wrote:
> > On Wed, Mar 6, 2019 at 11:52 AM Russell King - ARM Linux admin
> > <linux@...linux.org.uk> wrote:
> > > On Wed, Mar 06, 2019 at 10:45:52AM +0100, Lucas Stach wrote:
> > > > Am Dienstag, den 05.03.2019, 17:31 +0000 schrieb Russell King - ARM Linux admin:
> > 
> > > > While I totally agree that the irqsteer driver should only default Y on
> > > > 64bit i.MX SoCs, I'm not really sure what to do about the Kconfig help
> > > > text.
> > > >
> > > > Enumerating SoCs in the Kconfig of a IP block driver is always prone to
> > > > get outdated. Just as the first example I've been able to come up with,
> > > > the MMC_SDHCI_ESDHC_IMX help text says: "This selects the Freescale
> > > > eSDHC/uSDHC controller support found on i.MX25, i.MX35 i.MX5x and
> > > > i.MX6x.", while the same IP block is to be found on i.MX7 and various
> > > > i.MX8.
> > > >
> > > > For the Kconfig user, who needs to decide if an option is relevant,
> > > > outdated SoC information is probably just as bad as no information at
> > > > all.
> > >
> > > How about "This option does not apply to AArch32 based SoCs" or
> > 
> > Negative is usually error prone.
> > 
> > > "This option should be enabled for i.MX7 and later SoCs" ?
> > 
> > Why it should be? It can / could be I guess.
> 
> I've no idea.  I'm just making suggestions - if you have anything
> better, let's hear it.

In case it isn't clear, this is the *exact* point here - I don't know
whether this option should be enabled for iMX6 or not, and the only
way I found out was to grep the dts files in arch/arm/boot/dts for
the driver's compatible string.  What that reveals is that *no* 32-bit
dts files contain the compatible string, and so I summise that *no*
32-bit iMX SoC should have this driver enabled.

Given that I don't know for certain, _I_ can't write a proper help
text for this - I can only make suggestions which _might_ fit what
the reality actually is.

The excuse that "we can't list the explicit SoCs" to me seems to be
a very lame excuse for a poor, one line help text that says absolutely
nothing that can't already be gathered from the option line itself.
So the current help text might as well be deleted - it's that "useful".

The best that I can come up with right now, given what little I know
from grepping the 32-bit DTS files, is that the help text should at
least indicate that it *isn't* applicable to 32-bit SoCs, or if you
prefer, *is* applicable to 64-bit SoCs.  Beyond that, I have no
information to formulate a better suggestion.

This is precisely why I say that we need to be smarter about Kconfig
help text: if it gives no useful information, it might as well not
even exist, and we might as well be honest and have Kconfig say that
there is no help available for the option.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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