linux-kernel - Re: [PATCH 0/7] char/mei: Intel MEI Driver

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Message-Id: <201103241410.53871.arnd@arndb.de>
Date:	Thu, 24 Mar 2011 14:10:53 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	"Weil, Oren jer" <oren.jer.weil@...el.com>
Cc:	Greg KH <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"david@...dhou.se" <david@...dhou.se>
Subject: Re: [PATCH 0/7] char/mei: Intel MEI Driver

On Thursday 24 March 2011, Weil, Oren jer wrote:
> >For a simple example, look at drivers/watchdog/riowd.c (most other files in
> >that directory do as well), just replace the riowd_writereg() function in
> there
> >with one that calls an exported function from your hardware. This should
> >really be trivial to do.
> 
> our Watchdog is a FW Client (FW Feature) so in order to communicate with it
> we need 
> use the MEI Driver functions. (Send Connect Message, Send and Recv Data).
> AFAIK, I can't use sys_open/sys_write to communicate with the MEI Driver, I
> need to expose
> functions that handles all of that communication, right?

Yes. Use EXPORT_SYMBOL_GPL().

> >> So you need to add support to the watchdog infrastructure for this?
> >> For some reason I thought you could kick the watchdog from within
> >> kernel code, did I get this wrong?
> 
> >A watchdog must be triggered from user space, in Linux we do this by
> writing
> >to /dev/watchdog. If you did it from kernel space, the watchdog would not
> >detect the case where the system is half-broken and still able to trigger
> the
> >watchdog, but not do much beyond that.
> 
> The Intel AMT Watchdog is not like a regular Watchdog,  our interface is
> like regular watchdog (set timeout API, ping  API and etc..)
> But when the watchdog expired the system will not be reboot, the AMT
> Watchdog is sending a OOB Message/Event
> to remote management console and the console software can decide what to do.
> (it can notify the operator to check why
> the system hangs, it can send a OOB reboot command to reboot the hang system
> and etc...)

Close enough, I guess.

	Arnd
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