Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965006AbWEBVtN (ORCPT ); Tue, 2 May 2006 17:49:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964994AbWEBVtM (ORCPT ); Tue, 2 May 2006 17:49:12 -0400 Received: from soundwarez.org ([217.160.171.123]:38094 "EHLO soundwarez.org") by vger.kernel.org with ESMTP id S965006AbWEBVtL (ORCPT ); Tue, 2 May 2006 17:49:11 -0400 Date: Tue, 2 May 2006 23:49:08 +0200 From: Kay Sievers To: Greg KH Cc: Kyle Moffett , Michael Holzheu , akpm@osdl.org, schwidefsky@de.ibm.com, penberg@cs.helsinki.fi, ioe-lkml@rameria.de, joern@wohnheim.fh-wedel.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] s390: Hypervisor File System Message-ID: <20060502214908.GB18192@vrfy.org> References: <20060428112225.418cadd9.holzheu@de.ibm.com> <20060429075311.GB1886@kroah.com> <8A7D2F4D-5A05-4C93-B514-03268CAA9201@mac.com> <20060429215501.GA9870@kroah.com> <4237705F-E1B2-46CF-BE66-EFB77F68EC42@mac.com> <20060501203815.GE19423@kroah.com> <2DBA690E-B11A-478E-B2E0-0529F4CE45A9@mac.com> <20060502040053.GA14413@kroah.com> <13D6E299-061B-46A5-A3CD-12E1075B9451@mac.com> <20060502213043.GB30957@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060502213043.GB30957@kroah.com> User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2163 Lines: 47 On Tue, May 02, 2006 at 02:30:43PM -0700, Greg KH wrote: > On Tue, May 02, 2006 at 04:48:42AM -0400, Kyle Moffett wrote: > > On May 2, 2006, at 00:00:53, Greg KH wrote: > > >On Mon, May 01, 2006 at 07:29:23PM -0400, Kyle Moffett wrote: > > >>So my question stands: What is the _recommended_ way to handle > > >>simple data types in low-bandwidth/frequency multiple-valued > > >>transactions to hardware? Examples include reading/modifying > > >>framebuffer settings (currently done through IOCTLS), s390 current > > >>state (up for discussion), etc. In these cases there needs to be > > >>an atomic snapshot or write of multiple values at the same time. > > >>Given the situation it would be _nice_ to use sysfs so the admin > > >>can do it by hand; makes things shell scriptable and reduces the > > >>number of binary compatibility issues. > > > > > >I really don't know of a way to use sysfs for this currently, and > > >hence, am not complaining too much about the different /proc files > > >that have this kind of information in it at the moment. > > > > > >If you or someone else wants to come up with some kind of solution > > >for it, I'm sure that many people would be very happy to see it. > > > > Hmm, ok; I'll see what I can come up with. Would anybody object to > > this kind of API (as in my previous email) that uses an open fd as a > > transaction "handle"? > > No, I think Kay played around with something like using the open fd of > the directory as such a lock (or was he using flock on it, I can't > remember now...) If you can assume that processes accessing the values are cooperative, it already works without any changes: $ time flock /sys/class/firmware echo 1 > /sys/class/firmware/timeout real 0m0.005s $ flock /sys/class/firmware sleep 5& [1] 6468 $ time flock /sys/class/firmware echo 1 > /sys/class/firmware/timeout real 0m3.558s Kay - 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/