linux-kernel - Re: [PATCH] applesmc: add sysfs file to report OSK

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Date:	Mon, 10 Dec 2012 22:30:08 +0100
From:	Rene Rebe <rene@...ctcode.com>
To:	Alexander Graf <agraf@...e.de>
Cc:	Henrik Rydberg <rydberg@...omail.se>,
	Guenter Roeck <groeck-dsl@...global.net>,
	"Gabriel L. Somlo" <somlo@....edu>,
	"khali@...ux-fr.org" <khali@...ux-fr.org>,
	"linux@...ck-us.net" <linux@...ck-us.net>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] applesmc: add sysfs file to report OSK


On 10.12.2012, at 22:24, Alexander Graf wrote:

> On 10.12.2012, at 21:43, Rene Rebe <rene@...ctcode.com> wrote:
> 
>> On 10.12.2012, at 21:19, Alexander Graf <agraf@...e.de> wrote:
>>> 
>>> On 10.12.2012, at 20:54, Henrik Rydberg wrote:
>>> 
>>>> Hi Guenter,
>>>> 
>>>>> On Mon, Dec 10, 2012 at 09:51:35AM -0500, Gabriel L. Somlo wrote:
>>>>>> The AppleSMC contains two char[32] keys, OSK0 and OSK1, which are not
>>>>>> reported in the key count and index by default. These keys are used by
>>>>>> the OS X boot sequence, and normally don't matter when running Linux.
>>>>>> 
>>>>>> This patch creates a sysfs entry which reports the value of these keys
>>>>>> as an ASCII string, to help emulators (such as QEMU) load OS X when
>>>>>> running on genuine Apple hardware.
>>>>>> 
>>>>>> Signed-off-by: Gabriel L. Somlo <somlo@....edu>
>>>>>> ---
>>>>>> 
>>>>>> For extra context: To boot OS X as a guest, QEMU must (among others)
>>>>>> emulate the AppleSMC. To boot successfully, OS X insists on querying
>>>>>> the (emulated) SMC for the value of OSK0 and OSK1. Currently, these
>>>>>> values must be supplied on the QEMU command line as
>>>>>> 
>>>>>> -device applesmc,osk="...concatenated values of OSK0 and OSK1..."
>>>>>> 
>>>>>> With the availability of /sys/devices/platform/applesmc.768/osk, the
>>>>>> emulated QEMU AppleSMC could acquire this string directly from the
>>>>>> (Apple-manufactured) host machine.
>>>>> Hmm ... this is a non-hwmon attribute which doesn't really belong into hwmon
>>>>> in the first place ... like several other attributes in the same driver.
>>>>> 
>>>>> So I'll leave it up to the maintainer to decide if we should accept it. Henrik ?
>>>> 
>>>> Indeed, the reaons against this patch are too many. I was just about
>>>> to reply with the below:
>>>> 
>>>> Gabriel,
>>>> 
>>>> The OSK string seems constant accross machines, which renders the
>>>> patch rather pointless, no? And even if the OSK differs between a
>>>> couple of machines, the emulator could easily handle it gracefully.
>>> 
>>> The point is that the return value of the OSK is a copyrighted string, we can not include in any other layer. The only way to make this legally savvy is to read the key from the host.
>>> 
>>>> 
>>>> There are also some technical issues with the patch below, to keep in
>>>> mind for future submissions.
>>> 
>>> Sigh - most of the comments below go back to earlier review from me. He basically had a version almost exactly like what you're asking him to do :). Funny how code style taste differs.
>> 
>> And this is exactly the reason why I'm less and less motivated to waste my lifetime with upstream work ...
> 
> It's nit that bad really. Gabriel can just send his earlier version again with the ret variable name changed and then it shouldn't be an issue to get it in.
> 
> Reading the key really is an important bit in creating a legally safe and easy method to virtualize Mac OS X on Linux. Just believe us on this one :).

Sure, you do not need to convince me about that ;-)

-- 
  René Rebe, ExactCODE GmbH, Jaegerstr. 67, DE-10117 Berlin
  http://exactcode.com | http://t2-project.org | http://rene.rebe.de

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