From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934763AbbI2MSA (ORCPT ); Tue, 29 Sep 2015 08:18:00 -0400 Received: from mail-wi0-f175.google.com ([209.85.212.175]:36314 "EHLO mail-wi0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756074AbbI2MRl (ORCPT ); Tue, 29 Sep 2015 08:17:41 -0400 Subject: Re: [PATCH v3 1/7] acpi: Add early device probing infrastructure To: Marc Zyngier References: <1443451758-22717-1-git-send-email-marc.zyngier@arm.com> <1443451758-22717-2-git-send-email-marc.zyngier@arm.com> <560A13FC.4080204@linaro.org> <20150929082906.2cabe51a@arm.com> Cc: "Rafael J. Wysocki" , Len Brown , Hanjun Guo , Tomasz Nowicki , Thomas Gleixner , Jason Cooper , Lorenzo Pieralisi , Sudeep Holla , Will Deacon , Catalin Marinas , linaro-acpi@lists.linaro.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org From: Daniel Lezcano Message-ID: <560A8161.1060808@linaro.org> Date: Tue, 29 Sep 2015 14:17:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux i686; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20150929082906.2cabe51a@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/29/2015 09:29 AM, Marc Zyngier wrote: > On Tue, 29 Sep 2015 06:30:52 +0200 > Daniel Lezcano wrote: > >> >> Hi Marc, >> >> On 09/28/2015 04:49 PM, Marc Zyngier wrote: >>> IRQ controllers and timers are the two types of device the kernel >>> requires before being able to use the device driver model. >>> >>> ACPI so far lacks a proper probing infrastructure similar to the one >>> we have with DT, where we're able to declare IRQ chips and >>> clocksources inside the driver code, and let the core code pick it up >>> and call us back on a match. This leads to all kind of really ugly >>> hacks all over the arm64 code and even in the ACPI layer. >>> >>> In order to allow some basic probing based on the ACPI tables, >>> introduce "struct acpi_probe_entry" which contains just enough >>> data and callbacks to match a table, an optional subtable, and >>> call a probe function. A driver can, at build time, register itself >>> and expect being called if the right entry exists in the ACPI >>> table. >>> >>> A acpi_probe_device_table() is provided, taking an identifier for >>> a set of acpi_prove_entries, and iterating over the registered >>> entries. >>> >>> Signed-off-by: Marc Zyngier >>> --- >>> drivers/acpi/scan.c | 39 +++++++++++++++++++++++ >>> include/asm-generic/vmlinux.lds.h | 10 ++++++ >>> include/linux/acpi.h | 66 +++++++++++++++++++++++++++++++++++++++ >>> 3 files changed, 115 insertions(+) >>> >>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c >>> index f834b8c..daf9fc8 100644 >>> --- a/drivers/acpi/scan.c >>> +++ b/drivers/acpi/scan.c >>> @@ -1913,3 +1913,42 @@ int __init acpi_scan_init(void) >>> mutex_unlock(&acpi_scan_lock); >>> return result; >>> } >>> + >>> +static struct acpi_probe_entry *ape; >>> +static int acpi_probe_count; >>> +static DEFINE_SPINLOCK(acpi_probe_lock); >>> + >>> +static int __init acpi_match_madt(struct acpi_subtable_header *header, >>> + const unsigned long end) >>> +{ >>> + if (!ape->subtable_valid || ape->subtable_valid(header, ape)) >>> + if (!ape->probe_subtbl(header, end)) >>> + acpi_probe_count++; >>> + >>> + return 0; >>> +} >>> + >>> +int __init __acpi_probe_device_table(struct acpi_probe_entry *ap_head, int nr) >>> +{ >>> + int count = 0; >>> + >>> + if (acpi_disabled) >>> + return 0; >>> + >>> + spin_lock(&acpi_probe_lock); >>> + for (ape = ap_head; nr; ape++, nr--) { >>> + if (ACPI_COMPARE_NAME(ACPI_SIG_MADT, ape->id)) { >>> + acpi_probe_count = 0; >>> + acpi_table_parse_madt(ape->type, acpi_match_madt, 0); >> >> Isn't supposed 'acpi_table_parse_madt' to return the count ? and >> shouldn't the return code be checked ? > > acpi_table_madt_parse() returns the count of the entries it has parsed. > We're interested in the count of entries that have been successfully > probed. Not quite the same thing. > > As for the return code, checking it is highly symbolic, because there > is no way we can recover from an error in the ACPI parsing - we're > dead anyway, as we end up without interrupt controller. I can add a > WARN_ON(), but I'm not sure more noise will help understanding the > problem. > > There is also the perfectly valid case where ACPI has been forcefully > disabled (or on arm64, not forcefully enabled). In which case, the > parsing code will abort early, and there is no reason to scream about > it. I see. Thanks for the details. - Daniel -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog