linux-kernel - Re: [PATCH 06/38] Annotate hardware config module parameters in drivers/clocksource/

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Date:   Wed, 19 Apr 2017 16:33:05 +0100
From:   David Howells <dhowells@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     dhowells@...hat.com, LKML <linux-kernel@...r.kernel.org>,
        gnomes@...rguk.ukuu.org.uk, gregkh@...uxfoundation.org,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        Jens Rottmann <JRottmann@...PERTEmbedded.de>,
        Andres Salomon <dilinger@...ued.net>
Subject: Re: [PATCH 06/38] Annotate hardware config module parameters in drivers/clocksource/

Hi Thomas,

Thomas Gleixner <tglx@...utronix.de> wrote:

> > --- a/drivers/clocksource/cs5535-clockevt.c
> > +++ b/drivers/clocksource/cs5535-clockevt.c
> > @@ -22,7 +22,7 @@
> >  #define DRV_NAME "cs5535-clockevt"
> >  
> >  static int timer_irq;
> > -module_param_named(irq, timer_irq, int, 0644);
> > +module_param_hw_named(irq, timer_irq, int, irq, 0644);
> >  MODULE_PARM_DESC(irq, "Which IRQ to use for the clock source MFGPT ticks.");
> 
> I'm not sure about this. AFAIR the parameter is required to work on
> anything else than some arbitrary hardware which has it mapped to 0.
> 
> Cc'ed people who might know.

Given what Jens said:

	Parameter defaults to 0, which means:
	1. autodetect (=keep IRQ BIOS has set up)
	2. if that fails use CONFIG_CS5535_MFGPT_DEFAULT_IRQ
	(see drivers/misc/cs5535-mfgpt.c: cs5535_mfgpt_set_irq())

	Autodetect works fine for our (ex-LiPPERT, now ADLINK) COTS boards:
	Linux auto-uses IRQ chosen in BIOS Setup. Wouldn't know about other
	companies, of course, but (2.) means parameter can be avoided via make
	menuconfig.

are you willing to okay this?

David