linux-kernel - Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.

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Date:	Mon, 17 Dec 2007 14:31:15 +0100
From:	Rene Herman <rene.herman@...il.com>
To:	Pavel Machek <pavel@....cz>
CC:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Paul Rolland <rol@...917.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"David P. Reed" <dpreed@...d.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	rol@...be.net
Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.

On 17-12-07 14:31, Pavel Machek wrote:

> On Mon 2007-12-17 14:22:26, Rene Herman wrote:
>> On 17-12-07 14:09, Ingo Molnar wrote:
>>
>>>>> -#ifndef CONFIG_UDELAY_IO_DELAY
>>>>> -static int __init dmi_alternate_io_delay_port(const struct 
>>>>> dmi_system_id *id)
>>>>> +static int __init dmi_io_delay_0xed_port(const struct dmi_system_id 
>>>>> *id)
>>>>>  {
>>>>> -	printk(KERN_NOTICE "%s: using alternate I/O delay port\n", id->ident);
>>>>> -	io_delay = alternate_io_delay;
>>>>> +	printk(KERN_NOTICE "%s: using 0xed I/O delay port\n", id->ident);
>>>>> +	io_delay_type = CONFIG_IO_DELAY_TYPE_0XED;
>>>>> +
>>>>>  	return 0;
>>>>>  }
>>>> This isn't correct. DMI shouldn't override the CONFIG choice or someone 
>>>> with matching DMI will have a defective CONFIG option. That's why I put 
>>>> all of it inside #ifndef.
>>> no, the DMI quirk is just that: a quirk that makes boxes work. The DMI 
>>> quirk takes precedence over just about any .config default, except an 
>>> explicit boot-commandline override.
>> No, most definitely not. Having the user select udelay or none through the 
>> kernel config and then the kernel deciding "ah, you know what, I'll know 
>> better and use port access anyway" is _utterly_ broken behaviour. Software 
>> needs to listen to its master.
> 
> That's what command line is for. Ingo is right here.

No. The kernel shouldn't provide defective config options.

Rene.
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