linux-kernel - Re: [PATCH] nubus: Unconditionally register bus type

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Date:   Mon, 7 May 2018 14:53:13 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Finn Thain <fthain@...egraphics.com.au>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nubus: Unconditionally register bus type

Hi Finn,

(responding immediately to patches doing non-kosher things ;-)

On Mon, May 7, 2018 at 1:57 AM, Finn Thain <fthain@...egraphics.com.au> wrote:
> On Sun, 6 May 2018, Greg Kroah-Hartman wrote:
>> > > Why not just have an "bus is registered" flag in your driver
>> > > register function that refuses to let drivers register with the
>> > > driver core if it isn't set?
>> >
>> > Perhaps that should happen in the core driver_register() function.
>> > BUG_ON is frowned upon, after all. Would that be acceptable?
>>
>> I don't understand what you mean here, perhaps make a patch to show it?
>>
>
> As an alternative to your suggestion (add flag to avoid the BUG_ON):
>
> --- a/drivers/base/driver.c
> +++ b/drivers/base/driver.c
> @@ -148,7 +148,10 @@ int driver_register(struct device_driver *drv)
>         int ret;
>         struct device_driver *other;
>
> -       BUG_ON(!drv->bus->p);
> +       if (!drv->bus->p) {
> +               WARN_ONCE(1, "Cannot register driver with invalid bus\n");
> +               return -EPROBE_DEFER;
> +       }
>
>         if ((drv->bus->probe && drv->probe) ||
>             (drv->bus->remove && drv->remove) ||
>
> I'm not actually proposing this change; just responding to your question.

The bus_type.p field may be unused by some bus drivers, hence this
would prevent their drivers from being registered.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds