Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754581AbbEMRzH (ORCPT ); Wed, 13 May 2015 13:55:07 -0400 Received: from down.free-electrons.com ([37.187.137.238]:46430 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751441AbbEMRzE (ORCPT ); Wed, 13 May 2015 13:55:04 -0400 Date: Wed, 13 May 2015 19:50:34 +0200 From: Maxime Ripard To: Greg Kroah-Hartman Cc: Mark Brown , linux-kernel@vger.kernel.org, Hans de Goede , linux-spi@vger.kernel.org, Martin Sperl , Michal Suchanek Subject: Re: [PATCH] spi: Force the registration of the spidev devices Message-ID: <20150513175034.GC4004@lukather> References: <1431462804-30467-1-git-send-email-maxime.ripard@free-electrons.com> <20150513112604.GI3066@sirena.org.uk> <20150513153740.GC11677@kroah.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="5QAgd0e35j3NYeGe" Content-Disposition: inline In-Reply-To: <20150513153740.GC11677@kroah.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3045 Lines: 77 --5QAgd0e35j3NYeGe Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Greg, On Wed, May 13, 2015 at 08:37:40AM -0700, Greg Kroah-Hartman wrote: > On Wed, May 13, 2015 at 12:26:04PM +0100, Mark Brown wrote: > > On Tue, May 12, 2015 at 10:33:24PM +0200, Maxime Ripard wrote: > >=20 > > > While this is nicer than the DT solution because of its accurate hard= ware > > > representation, it's still not perfect because you might not have acc= ess to the > > > DT, or you might be driving a completely generic device (such as a > > > microcontroller) that might be used for something else in a different > > > context/board. > >=20 > > Greg, you're copied on this because this seems to be a generic problem > > that should perhaps be solved at a driver model level - having a way to > > bind userspace access to devices that we don't otherwise have a driver > > for. The subsystem could specify the UIO driver to use when no other > > driver is available. >=20 > That doesn't really work. I've been talking to the ACPI people about > this, and the problem is "don't otherwise have a driver for" is an > impossible thing to prove, as you never know when a driver is going to > be loaded from userspace. >=20 > You can easily bind drivers to devices today from userspace, why not > just use the built-in functionality you have today if you "know" that > there is no driver for this hardware. What we're really after here is that we want to have an spidev instance when we don't even have a device. And since SPI isn't really doing any kind of hotplug, the only situation that might be problematic is if we have the DT overlays registering new devices. Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com --5QAgd0e35j3NYeGe Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJVU47qAAoJEBx+YmzsjxAgykoP/jYonFs6kWgHcsaDK2E68fnC 0afbUWEWocyt455nRvPnuZT3b+tyDPIlmVzryxI5AB1apyDA7EqELWCn/SYu+zsK xMQPZyyxk1gLkVI+7huxiGDBvqezdJWjyzLUJA7eVJpe4qL4ByxaOYSIXKZokDfP udJxR5nIZtH2AhvXnq2rxFLQruVXmzUh8qmG7uGGgBdmjwAy926YLbPuKXUaM7s4 NLjT4dVTVEfpW2a8J0Uz0x1QZeNpBTrY0FpCS1xpdFIvtp5HmzvSf+dCD2ns1Lre 0VVe6D0SNxixyf/+8Z3fDkfneAUxLxSHuFXWiVXM4gazrVAjOd6ThjEwTY+1gKS2 nWOBMjNVj3htihI7yYMA1UW/KOVVPlWM8Qr81U+3EZDGJ2hx1LXuZpI3gkhK5D1J e6i6avSNDo1nSQ4+DGhSEqYIPkPIRKs7Lcqi5Yktm9a7qEyY60SHLqmNXHG7L2C9 aJxiWbDv4hBvV+r6h4HRptyceM4s+fpBNiWoHfqPwaWd5DbstfOaciOi/lCv+58r aI6b4TBul5va8inU7qUAq4eoLEA+VggpqQfnQIKwdZoEW8N8KFzMucJ72t8y1fEh uy52V2mKbc9O1IXdg3d8CNg8HutzE02Yytj1Dpq/1DtqdN40Z25R9nCb6284+JVF fDHFvUhfm9BqmuMcd04F =W2mn -----END PGP SIGNATURE----- --5QAgd0e35j3NYeGe-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/