From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752699Ab2G0SWA (ORCPT ); Fri, 27 Jul 2012 14:22:00 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:34853 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751965Ab2G0SV7 (ORCPT ); Fri, 27 Jul 2012 14:21:59 -0400 Date: Fri, 27 Jul 2012 11:21:55 -0700 From: Greg Kroah-Hartman To: Jean Delvare Cc: LKML Subject: Re: [PATCH/RFC] platform: Add support for automatic device IDs Message-ID: <20120727182155.GD23564@kroah.com> References: <20120727134625.71e29d2d@endymion.delvare> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120727134625.71e29d2d@endymion.delvare> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 27, 2012 at 01:46:25PM +0200, Jean Delvare wrote: > Right now we have support for explicit platform device IDs, as well as > ID-less platform devices when a given device type can only have one > instance. However there are cases where multiple instances of a device > type can exist, and their IDs aren't (and can't be) known in advance > and do not matter. In that case we need automatic device IDs to avoid > device name collisions. > > I am using magic ID value -4 for this (I left -2 and -3 free in case > we ever need a couple of other magic values.) The automatically > allocated device IDs are global (to avoid an additional per-driver > cost) and are stored internally as negative numbers, starting with -4. > This is required so that the IDs can be freed later. Externally the > positive value is used. > > Signed-off-by: Jean Delvare > Cc: Greg Kroah-Hartman > --- > If anyone has a problem with the -4 or using negative device IDs > internally, it would be possible to avoid that by adding a boolean > attribute to every platform device to record whether the ID needs to > be freed. This would cost some memory. A boolean is "free" don't worry about that. Don't overload the device id with "magic" values like this, I don't like that at all. I'd prefer to see another field added if this is really going to be needed. thanks, greg k-h