Messages in this thread | | | Subject | Re: [PATCH v3 1/7] acpi: Add early device probing infrastructure | From | Daniel Lezcano <> | Date | Tue, 29 Sep 2015 14:17:37 +0200 |
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On 09/29/2015 09:29 AM, Marc Zyngier wrote: > On Tue, 29 Sep 2015 06:30:52 +0200 > Daniel Lezcano <daniel.lezcano@linaro.org> 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 <marc.zyngier@arm.com> >>> --- >>> 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
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