From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id DF1C36B026E for ; Fri, 15 Dec 2017 21:15:44 -0500 (EST) Received: by mail-oi0-f72.google.com with SMTP id d76so4844233oig.12 for ; Fri, 15 Dec 2017 18:15:44 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id 20sor3125187otd.69.2017.12.15.18.15.43 for (Google Transport Security); Fri, 15 Dec 2017 18:15:44 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <20171214021019.13579-1-ross.zwisler@linux.intel.com> <20171214021019.13579-2-ross.zwisler@linux.intel.com> <1658696.rIK19Js0WO@aspire.rjw.lan> From: "Rafael J. Wysocki" Date: Sat, 16 Dec 2017 03:15:43 +0100 Message-ID: Subject: Re: [PATCH v3 1/3] acpi: HMAT support in acpi_parse_entries_array() Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: "Rafael J. Wysocki" , Linux ACPI , Ross Zwisler , "linux-kernel@vger.kernel.org" , "Anaczkowski, Lukasz" , "Box, David E" , "Kogut, Jaroslaw" , "Koss, Marcin" , "Koziej, Artur" , "Lahtinen, Joonas" , "Moore, Robert" , "Nachimuthu, Murugasamy" , "Odzioba, Lukasz" , "Rafael J. Wysocki" , "Schmauss, Erik" , "Verma, Vishal L" , "Zheng, Lv" , Andrew Morton , Balbir Singh , Brice Goglin , Dave Hansen , Jerome Glisse , John Hubbard , Len Brown , Tim Chen , Linux MM , "linux-nvdimm@lists.01.org" On Sat, Dec 16, 2017 at 2:57 AM, Dan Williams wrote: > On Fri, Dec 15, 2017 at 5:53 PM, Rafael J. Wysocki wrote: >> On Friday, December 15, 2017 2:10:17 AM CET Dan Williams wrote: >>> On Wed, Dec 13, 2017 at 6:10 PM, Ross Zwisler >>> wrote: >>> > The current implementation of acpi_parse_entries_array() assumes that each >>> > subtable has a standard ACPI subtable entry of type struct >>> > acpi_subtable_header. This standard subtable header has a one byte length >>> > followed by a one byte type. >>> > >>> > The HMAT subtables have to allow for a longer length so they have subtable >>> > headers of type struct acpi_hmat_structure which has a 2 byte type and a 4 >>> > byte length. >>> >>> Hmm, NFIT has a 2 byte type and a 2 byte length, so its one more >>> permutation. I happened to reinvent sub-table parsing in the NFIT >>> driver, but it might be nice in the future to refactor that to use the >>> common parsing. >>> >>> > >>> > Enhance the subtable parsing in acpi_parse_entries_array() so that it can >>> > handle these new HMAT subtables. >>> > >>> > Signed-off-by: Ross Zwisler >>> > --- >>> > drivers/acpi/tables.c | 52 ++++++++++++++++++++++++++++++++++++++++----------- >>> > 1 file changed, 41 insertions(+), 11 deletions(-) >>> > >>> > diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c >>> > index 80ce2a7d224b..f777b94c234a 100644 >>> > --- a/drivers/acpi/tables.c >>> > +++ b/drivers/acpi/tables.c >>> > @@ -218,6 +218,33 @@ void acpi_table_print_madt_entry(struct acpi_subtable_header *header) >>> > } >>> > } >>> > >>> > +static unsigned long __init >>> > +acpi_get_entry_type(char *id, void *entry) >>> > +{ >>> > + if (strncmp(id, ACPI_SIG_HMAT, 4) == 0) >>> > + return ((struct acpi_hmat_structure *)entry)->type; >>> > + else >>> > + return ((struct acpi_subtable_header *)entry)->type; >>> > +} >>> >>> It seems inefficient to make all checks keep asking "is HMAT?". >> >> Well, ideally, the signature should be checked once. I guess that can be >> arranged for here. >> >>> Especially if we want to extend this to other table types should we >>> instead setup and pass a pair of function pointers to parse the >>> sub-table format? >> >> Function pointers may be too much even. :-) > > True, how about an enum of acpi sub-table header types? That works. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org