netdev - RE: [PATCH net-next] mdio_bus: Remove unneeded gpiod NULL check

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Message-ID: <9235D6609DB808459E95D78E17F2E43D40B1B47F@CHN-SV-EXMX02.mchp-main.com>
Date:   Thu, 7 Sep 2017 21:51:11 +0000
From:   <Woojung.Huh@...rochip.com>
To:     <f.fainelli@...il.com>, <linus.walleij@...aro.org>
CC:     <andrew@...n.ch>, <festevam@...il.com>,
        <sergei.shtylyov@...entembedded.com>, <davem@...emloft.net>,
        <netdev@...r.kernel.org>, <fabio.estevam@....com>
Subject: RE: [PATCH net-next] mdio_bus: Remove unneeded gpiod NULL check

> >>> If someone is using GPIO descriptors with GPIO disabled, i.e. calling
> >>> gpiod_get() and friends, this is very likely to be a bug, and what
> >>> the driver wants to do is:
> >>>
> >>>  depends on GPIOLIB
> >>>
> >>> or
> >>>
> >>>  select GPIOLIB
> >>>
> >>> in Kconfig. The whole optional thing is mainly a leftover from when it
> >>> was possible to have a local implementation of the GPIOLIB API in
> >>> some custom header file, noone sane should be doing that anymore,
> >>> and if they do, they can very well face the warnings.
> >>>
> >>> If someone is facing a lot of WARN_ON() messages to this, it is a clear
> >>> indication that they need to fix their Kconfig and in that case it is proper.
> >> Linus & Andrew,
> >>
> >> I knew that it is already in David's pulling request.
> >> Configuring GPIOLIB is the right solution  even if platform doesn't use it?
> >
> > I guess?
> >
> > "Platform doesn't use it" what does that mean?
> >
> > Does it mean it does not call the
> > APIs of the GPIOLIB, does it mean it doesn't have a GPIO driver
> > at probe (but may have one by having it probed from a module)
> > or does it mean the platform can never have it?
> 
> I think it means CONFIG_GPIOLIB=n in the kernel because it's not needed,
> yet you run code (like drivers/net/phy/mdio_bus.c) that unconditionally
> calls into GPIOLIB and attempts to configure a given GPIO if available.
Yes. I'm facing issue on PC which won't need GPIOLIB as default.
Warning message goes away when GPIOLIB is enabled, and fortunately,
Ubuntu default config has it.
So, it may not be seen by many users when with full/default configuration.

> This thread is actually what prompted me to write this email:
>
> https://lkml.org/lkml/2017/9/2/3
Thanks for the link.