linux-kernel - Re: [PATCH v2] x86: i8237: Register based on FADT legacy boot flag

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Message-ID: <alpine.DEB.2.21.1803191152450.2010@nanos.tec.linutronix.de>
Date:   Mon, 19 Mar 2018 11:57:04 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Anshuman Gupta <anshuman.gupta@...el.com>
cc:     Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>, x86@...nel.org,
        mingo@...hat.com, hpa@...or.com, rjw@...ysocki.net,
        andriy.shevchenko@...ux.intel.com, linux-kernel@...r.kernel.org,
        Alan Cox <alan@...ux.intel.com>
Subject: Re: [PATCH v2] x86: i8237: Register based on FADT legacy boot flag

On Mon, 19 Mar 2018, Anshuman Gupta wrote:
> On Wed, Mar 14, 2018 at 04:07:43PM +0100, Thomas Gleixner wrote:
> > On Wed, 14 Mar 2018, Rajneesh Bhardwaj wrote:
> > > +	 * support 8237 DMA or bus mastering from LPC. Platform firmware
> > > +	 * must announce the support for such legacy devices via
> > > +	 * ACPI_FADT_LEGACY_DEVICES field in FADT table.
> > > +	 */
> > > +	if (!x86_platform.legacy.devices.pnpbios && dmi_get_bios_year() >= 2017)
> > 
> > Please use arch_pnpbios_disabled() and explain why you need that year
>   arch_pnpbios_disabled is defined only when CONFIG_PNPBIOS is set, which may 
>   not be true for all configurations.

The please create a helper function x86_pnpbios_disabled() and use that one
in arch_pnp_bios_disabled() and in your new code.

> > check. If there is no pnpbios then why is the year interesting and why
> > would anyone trust something which comes from BIOS?
>
>   Modern bios fsp have started using to use ACPI_FADT_LEGACY_DEVICES field in
>   FADT table, that is the reason we require a year check for BIOS.
>   https://review.coreboot.org/#/c/coreboot/+/23833/
>   https://review.coreboot.org/#/c/coreboot/+/23835/ 

Sorry, this gerrit stuff is unreadable. Please explain it in your own
words. You have to do that anyway as that information wants to be in a
comment or at least in the change log.

Thanks,

	tglx