From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755801Ab1KWSJA (ORCPT ); Wed, 23 Nov 2011 13:09:00 -0500 Received: from service87.mimecast.com ([91.220.42.44]:53702 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755652Ab1KWSI7 convert rfc822-to-8bit (ORCPT ); Wed, 23 Nov 2011 13:08:59 -0500 Subject: Re: [PATCH] virtio-mmio: Devices parameter parsing From: Pawel Moll To: Rusty Russell Cc: "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" In-Reply-To: <87fwhhx9is.fsf@rustcorp.com.au> References: <1321365185-2928-1-git-send-email-pawel.moll@arm.com> <87sjlooq3m.fsf@rustcorp.com.au> <1321467222.3137.417.camel@hornet.cambridge.arm.com> <87vcqe9ml9.fsf@rustcorp.com.au> <1321886688.3093.248.camel@hornet.cambridge.arm.com> <1321898210.3093.263.camel@hornet.cambridge.arm.com> <87fwhhx9is.fsf@rustcorp.com.au> Date: Wed, 23 Nov 2011 18:08:52 +0000 Message-ID: <1322071732.3093.491.camel@hornet.cambridge.arm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 X-OriginalArrivalTime: 23 Nov 2011 18:08:53.0160 (UTC) FILETIME=[F5785280:01CCAA0A] X-MC-Unique: 111112318085602601 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-11-22 at 00:53 +0000, Rusty Russell wrote: > > Any ideas? > Perhaps not today. So, we will need a linked list of devices and > resources. Yeah, that means allocating, which means YA > slab_is_available()/alloc_bootmem() hack. Hm. It doesn't sound like a good deal, really... Loads of tricks to get data I need quite late in the boot process... > Think of yourself as a pioneer... I had a vague idea of "late parameters" last night, which would be parsed once whole machinery is up and running. Will look around and try to propose something. On Tue, 2011-11-22 at 00:44 +0000, Rusty Russell wrote: > Or would it be simpler to enhance sscanf() with some weird format option > for suffixing? I haven't looked for similar cases, but I'd suspect a > big win in general. > > This would be neater than anything else we've got: > if (sscanf(device, "%llu@%llu[KMG]:%u", ...) != 3 > && sscanf(device, "%llu@%llu[KMG]:%u:%u", ...) != 4) > return -EINVAL; sscanf was a good hint! Thanks, why haven't I thought of it myself? ;-) That's what I came up with: static int vm_cmdline_set(const char *device, const struct kernel_param *kp) { struct resource resources[2] = {}; char *str; long long int base; int processed, consumed = 0; struct platform_device *pdev; resources[0].flags = IORESOURCE_MEM; resources[1].flags = IORESOURCE_IRQ; resources[0].end = memparse(device, &str) - 1; processed = sscanf(str, "@%lli:%u%n:%d%n", &base, &resources[1].start, &consumed, &vm_cmdline_id, &consumed); if (processed < 2 || processed > 3 || str[consumed]) return -EINVAL; resources[0].start = base; resources[0].end += base; resources[1].end = resources[1].start; The only bit missing from sscanf() would be some sort of "%m" format, which behaved like memparse and also processed unsigned number with "0 base" (hard to believe but the only "universal" - as in octal, dec and hex - format is %i, which is signed). But still, looks quite neat already :-) I'll try to have a look at the "late parameters" idea tomorrow. Any early warnings? Cheers! Pawel