linux-kernel - RE: [PATCH V3 02/10] init.h: Fix the __setup

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Message-ID: <DB3PR0402MB39161C372E869A670D115FBBF56C0@DB3PR0402MB3916.eurprd04.prod.outlook.com>
Date:   Wed, 1 Jul 2020 10:02:21 +0000
From:   Anson Huang <anson.huang@....com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        "oleksandr.suvorov@...adex.com" <oleksandr.suvorov@...adex.com>,
        Stefan Agner <stefan.agner@...adex.com>,
        Peng Fan <peng.fan@....com>, Abel Vesa <abel.vesa@....com>,
        Aisheng Dong <aisheng.dong@....com>,
        Andy Duan <fugang.duan@....com>,
        Daniel Baluta <daniel.baluta@....com>,
        YueHaibing <yuehaibing@...wei.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH V3 02/10] init.h: Fix the __setup_param() macro for module
 build

Hi, Arnd


> Subject: Re: [PATCH V3 02/10] init.h: Fix the __setup_param() macro for
> module build
> 
> On Wed, Jul 1, 2020 at 11:27 AM Anson Huang <anson.huang@....com>
> wrote:
> > > Subject: Re: [PATCH V3 02/10] init.h: Fix the __setup_param() macro
> > > for module build
> > >
> > > On Wed, Jul 1, 2020 at 7:14 AM Anson Huang <anson.huang@....com>
> > > wrote:
> > >
> > > I don't understand what your plan is here. Do you mean you will
> > > leave that part of the clk driver as built-in?
> >
> > I meant I will leave the #else block of __setup_param() defined as
> > nothing as below to make module build passed.
> >
> > #define __setup_param(str, unique_id, fn, early)        /* nothing */
> 
> No, I think that is  mistake. It will mean that other drivers with the same bug
> as the imx-clk driver will appear to build fine, but not work correctly.
> 
> A build error is better than silently dropping the command line parsing in my
> opinion.
> 
> > > This error just means you can't have a __setup_param() call in a
> > > loadable module, which we already knew. If you need to do something
> > > with the clocks early on, that has to be in built-in code and cannot
> > > be in a module. If you don't need that code, then you should just
> > > remove it from both the modular version and the built-in version.
> > >
> > > What is the purpose of that __setup_param() argument parsing in the
> > > clock driver?
> >
> > We need the code for proper uart clock management of earlycon, from
> > the code, it is trying to keep console uart clock enabled during kernel boot
> up.
> 
> Why not move this all to a separate file then and only build it when
> CONFIG_CLK_IMX=y?
> It seems that you don't need the imx_keep_uart_clocks_param() if the clk
> driver is loaded as a module, but then you also don't need the
> imx_clk_disable_uart() and imx_register_uart_clocks() functions or the
> associated variables.

If so, how about just adding "#ifndef MODULE" check for this part of code? I think
it should be easier/better than adding a file and build it conditionally?

Thanks,
Anson