linux-kernel - Re: [PATCH v2 2/7] x86/boot: Introduce helpers for serial I/O

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Message-ID: <20190328132855.GH22720@zn.tnic>
Date:   Thu, 28 Mar 2019 14:28:55 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/7] x86/boot: Introduce helpers for serial I/O

On Thu, Mar 28, 2019 at 03:11:40PM +0200, Andy Shevchenko wrote:
> Any idea how it can be done?

Like this?

static u8 serial_inb(unsigned long addr, int offset)
{
	if (early_serial_do_mmio) {
		asm volatile("movb %1,%0" : "=q" (v) : "m" (*(volatile u8 __force *)addr));

		return v;
	} else {
		 return inb(addr + offset);
	}
}

-- 
Regards/Gruss,
    Boris.

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