linux-kernel - Re: [PATCH v0 42/42] notifier: Return an error when callback is already registered

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Date:   Mon, 8 Nov 2021 16:58:57 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>,
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Subject: Re: [PATCH v0 42/42] notifier: Return an error when callback is
 already registered

On Mon, Nov 08, 2021 at 04:25:47PM +0100, Geert Uytterhoeven wrote:
> I'm not against returning proper errors codes.  I'm against forcing
> callers to check things that cannot fail and to add individual error
> printing to each and every caller.

If you're against checking things at the callers, then the registration
function should be void. IOW, those APIs are not optimally designed atm.

> Note that in other areas, we are moving in the other direction,
> to a centralized printing of error messages, cfr. e.g. commit
> 7723f4c5ecdb8d83 ("driver core: platform: Add an error message to
> platform_get_irq*()").

Yes, thus my other idea to add a lower level __notifier_chain_register()
to do the checking.

I'll see if I can convert those notifier registration functions to
return void, in the process. But let's see what the others think first.

Thanks for taking the time.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette