From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2F0B510F0
	for <patches@lists.linux.dev>; Wed, 20 Apr 2022 07:49:16 +0000 (UTC)
Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2EC32C385A1;
	Wed, 20 Apr 2022 07:49:15 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org;
	s=korg; t=1650440955;
	bh=f//ddCb1kg1OUp3nBiyVRIMPPYnTIOUqEVT0YxYxFNY=;
	h=Date:From:To:Cc:Subject:References:In-Reply-To:From;
	b=pOlkMTGMogFALyUhAiodmRVJkTER+iPBmeuHteiMlxC8bXyAVLZqqCgaYPtpflvTC
	 QS4Kd3pUP+RF7B2cyWw9fMkwf9ZqW8ZFLqE9m4BhKpFgQKwFpwNhzu42stTQdbacpX
	 BRqOhbJ7X2mZ1wjgYIBxU59iBp4C8mUKdyJFZIKk=
Date: Wed, 20 Apr 2022 09:49:13 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Tony Luck <tony.luck@intel.com>, Hans de Goede <hdegoede@redhat.com>,
	markgross@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>, X86 ML <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Jonathan Corbet <corbet@lwn.net>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	"Joseph, Jithu" <jithu.joseph@intel.com>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux Doc Mailing List <linux-doc@vger.kernel.org>,
	platform-driver-x86@vger.kernel.org, patches@lists.linux.dev,
	Ravi V Shankar <ravi.v.shankar@intel.com>
Subject: Re: [PATCH v3 03/11] platform/x86/intel/ifs: Create device for Intel
 IFS (In Field Scan)
Message-ID: <Yl+6+fhMkAj1Jn0p@kroah.com>
References: <20220407191347.9681-1-jithu.joseph@intel.com>
 <20220419163859.2228874-1-tony.luck@intel.com>
 <20220419163859.2228874-4-tony.luck@intel.com>
 <Yl7npfrVTPFEIivC@kroah.com>
 <CAPcyv4jzscs3Dg4QN0+XHRYdekBeqy1=dRX-mWCj1OXo8jS2vQ@mail.gmail.com>
 <CAPcyv4hBGgN=LqY55nf2K4E1OD0n=_axri4CNSKVneStYEp6rw@mail.gmail.com>
Precedence: bulk
X-Mailing-List: patches@lists.linux.dev
List-Id: <patches.lists.linux.dev>
List-Subscribe: <mailto:patches+subscribe@lists.linux.dev>
List-Unsubscribe: <mailto:patches+unsubscribe@lists.linux.dev>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAPcyv4hBGgN=LqY55nf2K4E1OD0n=_axri4CNSKVneStYEp6rw@mail.gmail.com>

On Tue, Apr 19, 2022 at 03:28:26PM -0700, Dan Williams wrote:
> On Tue, Apr 19, 2022 at 11:09 AM Dan Williams <dan.j.williams@intel.com> wrote:
> >
> > On Tue, Apr 19, 2022 at 9:48 AM Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Tue, Apr 19, 2022 at 09:38:51AM -0700, Tony Luck wrote:
> > > > The initial implementation of IFS is model specific. Enumeration is
> > > > via a combination of family-model-stepping and a check for a bit in the
> > > > CORE_CAPABILITIES MSR.
> > > >
> > > > Linux has handled this lack of enumeration before with a code stub to
> > > > create a device.  See arch/x86/kernel/pmem.c. Use the same approach
> > > > here.
> > >
> > > Ick, why?  Why not just create a simple virtual device and use that?  Do
> > > you really want to bind a driver to this?  Or do you already "know" the
> > > only driver that you have will bind to this?
> >
> > With the realization that there may be multiple instances of an
> > IFS-like capability going forward, and that ideally those capabilities
> > would move away from a CPU capability bit to an ACPI description, then
> > it seemed to me that a simulated platform_device for this is a
> > reasonable fit. I.e. when / if an ACPI _HID is assigned for this
> > capability the same platform_driver can be reused for those instances.
> 
> Turns out the ACPI enumeration for this may not materialize, so this
> can indeed move to a simple / driver-less device.

Hey, see, doing extra work now was not a good idea :)