linux-kernel - Re: [PATCH] soc: imx-scu: Support module build

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Date:   Thu, 18 Jun 2020 09:20:52 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Anson Huang <anson.huang@....com>
Cc:     Aisheng Dong <aisheng.dong@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        Peng Fan <peng.fan@....com>,
        Leonard Crestez <leonard.crestez@....com>,
        "krzk@...nel.org" <krzk@...nel.org>,
        Daniel Baluta <daniel.baluta@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH] soc: imx-scu: Support module build

On Wed, Jun 17, 2020 at 11:41 AM Anson Huang <anson.huang@....com> wrote:

> > >
> > > I'm ok with the change. But I'm curious how can this module be
> > > autoloaded without MODULE_DEVICE_TABLE.
> > > Have you tested if it can work?
> > >
> >
> > I ONLY tested the manual insmod, if want to support auto load, may need
> > some more change, will try it later and send out a V2 if needed.
>
> The further check shows that, if want to support auto load, the platform device
> register needs to be done in somewhere else which is built-in (in my test, I move it
> to clk-imx8qxp.c's probe), and also need to add below module alias in this driver,
> because it has no device node in DT and no device table in driver.
>
> +MODULE_ALIAS("platform:imx-scu-soc");
>
> Since this driver has no device node in DT, and the target is to build all SoC specific
> drivers as module, so the best way is to add a virtual device node in DT in order to support
> auto load?

I see that there is indeed a driver for the device node in
drivers/firmware/imx/imx-scu.c,
the only reason for this module using device_initcall() with a manual
platform_device_register_simple() seems to be that we cannot have two
platform drivers bind to the same device node.

I think a cleaner way to handle this would be to just move the entire soc
driver into the firmware driver and then remove the duplication.

       Arnd