From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753653AbZLCIaJ (ORCPT ); Thu, 3 Dec 2009 03:30:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753562AbZLCIaI (ORCPT ); Thu, 3 Dec 2009 03:30:08 -0500 Received: from poutre.nerim.net ([62.4.16.124]:64375 "EHLO poutre.nerim.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753239AbZLCIaH (ORCPT ); Thu, 3 Dec 2009 03:30:07 -0500 Date: Thu, 3 Dec 2009 09:30:09 +0100 From: Jean Delvare To: Dmitry Torokhov Cc: LKML , Tejun Heo , Jeff Garzik , "Rafael J. Wysocki" , "H. Peter Anvin" Subject: Re: [PATCH] DMI: allow omitting ident strings in DMI tables Message-ID: <20091203093009.059197a6@hyperion.delvare> In-Reply-To: <20091203031240.GB9121@core.coreip.homeip.net> References: <20091203031240.GB9121@core.coreip.homeip.net> X-Mailer: Claws Mail 3.5.0 (GTK+ 2.14.4; i586-suse-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dmitry, On Wed, 2 Dec 2009 19:12:40 -0800, Dmitry Torokhov wrote: > The purpose of dmi->ident is twofold - it may be used by DMI callback > functions when composing log messages; it is also used to determine > end of DMI table in dmi_check_system() and dmi_first_match(). However, > in case when callbacks are not interested in using ident at all it just > wastes memory. Let's consider entries with empty ident but initialized > first match slot as a valid entry and not as end-of-table marker. You are free to use an empty string ("") as the ident. This will use 1 byte of memory, I'm sure you can afford it. struct dmi_system_id is 332 bytes large on 32-bit systems (344 on 64-bit systems), and we use such an empty structure as the list terminator. So I really doubt we care about the extra few bytes used by the ident strings. > > Signed-off-by: Dmitry Torokhov > --- > > CCed a few random people since they touched dmi code in the last few > months... > > drivers/firmware/dmi_scan.c | 13 +++++++++++-- > 1 files changed, 11 insertions(+), 2 deletions(-) > > > diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c > index 938100f..9116aa7 100644 > --- a/drivers/firmware/dmi_scan.c > +++ b/drivers/firmware/dmi_scan.c > @@ -440,6 +440,15 @@ static bool dmi_matches(const struct dmi_system_id *dmi) > } > > /** > + * dmi_is_end_of_table - check for end-of-table marker > + * @dmi: pointer to the dmi_system_id structure to check > + */ > +static bool dmi_is_end_of_table(const struct dmi_system_id *dmi) > +{ > + return dmi->ident == NULL && dmi->matches[0].slot == DMI_NONE; If you really want to allow for dmi->ident == NULL, then I guess you can _only_ check for dmi->matches[0].slot == DMI_NONE. I can't think of any legitimate use of DMI_NONE for a used slot. The only thing you have to do then is to ensure that DMI_NONE = 0 in (I'm not sure if any C standard guarantees that enums starts at 0.) There's a possible optimization in dmi_matches(), BTW: DMI_NONE should break, not continue. -- Jean Delvare