linux-kernel - Re: [PATCH V3 04/10] clk: imx: Support building SCU clock driver as module

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Date:   Mon, 29 Jun 2020 17:08:10 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Anson Huang <anson.huang@....com>
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 04/10] clk: imx: Support building SCU clock driver as module

On Mon, Jun 29, 2020 at 4:52 PM Anson Huang <anson.huang@....com> wrote:
> > Subject: Re: [PATCH V3 04/10] clk: imx: Support building SCU clock driver as module
> > On Mon, Jun 29, 2020 at 2:53 PM Anson Huang <anson.huang@....com> wrote:
> >
> > Sorry, I misread the patch in multiple ways. First of all, you already put
> > clk-scu.o and clk-lpcg-scu.o files into a combined loadable module, and I had
> > only looked at clk-scu.c.
> >
> > What I actually meant here was to link clk-scu.o together with clk-imx8qxp.o
> > (and possibly future chip-specific files) into a loadable module and drop the
> > export.
>
> Sorry, could you please advise more details about how to do it in Makefile?
> I tried below but it looks like NOT working. multiple definition of module_init() error reported.
>
> obj-$(CONFIG_MXC_CLK_SCU) := clk-imx.o
> clk-imx-y += clk-scu.o clk-lpcg-scu.o
> clk-imx-$(CONFIG_CLK_IMX8QXP) += clk-imx8qxp.o clk-imx8qxp-lpcg.o

Right, you can't have multiple module_init() in a module, so what I suggested
earlier won't work any more as soon as you add a second chip that uses the
clk-scu driver, and then you have to use separate modules, or some hack
that calls the init functions one at a time, which is probably worse.

If it's only imx8qxp, you can do it like this:

obj-$(CONFIG_MXC_CLK_SCU) := clk-imx-scu.o clk-imx-lpcg.o
clk-imx-scu-y         += clk-scu.o clk-imx8qxp.o
clk-imx-lpcq-scu-y += clk-lpcg-scu.o clk-imx8qxp-lpcg.o

If you already know that the scu driver is going to be used in future
chips, then just stay with what you have now, using a separate module
per file, exporting the symbols as needed.

        Arnd