linux-kernel - Re: [PATCH v2] x86/earlyprintk: Add a force option for pciserial device

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Date:   Mon, 1 Oct 2018 22:18:10 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        H Peter Anvin <hpa@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Stuart R . Anderson" <stuart.r.anderson@...el.com>,
        alan@...ux.intel.com, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86/earlyprintk: Add a force option for pciserial
 device

Hi Boris,

On Mon, Oct 01, 2018 at 02:39:16PM +0200, Borislav Petkov wrote:
> On Sun, Sep 30, 2018 at 09:16:19PM +0800, Feng Tang wrote:
> > Got your point. As the following [,baudrate] is also optional, and this
> > "force" could be the last option for pciserial. The check may be
> > 
> > 	if (!strncmp(s, "force,", 6) || !strncmp(s, "force ", 6)) {
> > 		force = 1;
> > 		s += 6;
> > 	}
> 
> You have !strncmp(s, "force,", 6) twice in there. I have no clue what
> you're trying to say.

I was trying to address your last comments:

"No, you need to force the presence of "," otherwise cmdlines like this:

earlyprintk=pciserial,0:XX.X,forcedoodoo

work too."

As I rechecked, the baud rate for pciserial is optional, so there may
be no ",baudrate" following the "force". So this 2 strncmp is to
cover conditions for with and without baudrate.

> 
> > Do you mean this? 
> > 
> > 	if (((classcode >> 16 != PCI_CLASS_COMMUNICATION_MODEM) &&
> > 	     (classcode >> 16 != PCI_CLASS_COMMUNICATION_SERIAL)) ||
> > 	   (((classcode >> 8) & 0xff) != 0x02)) /* 16550 I/F at BAR0 */ {
> > 		if (!force)
> > 			return;
> > 	}
> 
> Yes.

Ok, thanks


Thanks,
Feng