From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933553AbXGSDrZ (ORCPT ); Wed, 18 Jul 2007 23:47:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757162AbXGSDrS (ORCPT ); Wed, 18 Jul 2007 23:47:18 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:59456 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758209AbXGSDrR (ORCPT ); Wed, 18 Jul 2007 23:47:17 -0400 Date: Wed, 18 Jul 2007 20:47:06 -0700 From: Andrew Morton To: Robin Getz Cc: "Mike Frysinger" , linux-kernel@vger.kernel.org Subject: Re: early_printk accessing __log_buf Message-Id: <20070718204706.42a02272.akpm@linux-foundation.org> In-Reply-To: <200707182337.34767.rgetz@blackfin.uclinux.org> References: <200707181756.44074.rgetz@blackfin.uclinux.org> <200707181939.46910.rgetz@blackfin.uclinux.org> <8bd0f97a0707181653j3d44aab2tf8b6d24689458023@mail.gmail.com> <200707182337.34767.rgetz@blackfin.uclinux.org> X-Mailer: Sylpheed 2.4.1 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 18 Jul 2007 23:37:34 -0400 Robin Getz wrote: > On Wed 18 Jul 2007 19:53, Mike Frysinger pondered: > > On 7/18/07, Robin Getz wrote: > > > On Wed 18 Jul 2007 18:16, Andrew Morton pondered: > > > > I'd suggest that any interface into here should be via function calls, > > > > not via direct access to printk internals: think up some nice > > > > copy_me_some_of_the_log_buffer() interface. > > > > > > If so - I would still like to put it in: > > > - ifdef CONFIG_EARLY_PRINTK > > > - and define as __init > > > > > > so that people don't use it when they shouldn't (when the kernel is up an > > > running). > > > > > > Something simple like - early_copy_log_buff(void *dest, size_t n) > > > > > > copies n bytes from log_buf to memory area dest. Returns number of bytes that > > > could not be copied. Can find out how many bytes are in the log_buff by > > > calling with zero size. > > > > > > This is not destructive to existing interfaces (log_start and con_start are > > > not updated/used). This should ensure that if booting does work - that normal > > > messages come out the standard method. > > > > > > Any other suggestions? > > > > maybe something as cheesy as early_get_log_buf() ? that way you dont > > have to do any buffer management, you can just operate read-only on > > the string ... > > I actually thought I might just do something like: > > char *c; > while (early_copy_log_buff(c, 1)) > out_early_serial_byte(c); > > that way - I don't need to be very complex in the arch code. > > That is about as cheesy/easy as I could think of... > Let's forget the "early" stuff - there are applications of this at oops-time as well, and that's as late as it gets ;) How about int log_buf_read(int index, char *my_char); You pass it a zero to start off, and it returns 0 or -1 if `index' is out of bounds. Probably we'd also need a log_buf_size(int) to find out how much is in there at present (for people who want to read the last 1000 bytes). Something simple and general, anyway.