ACPI: Add early device probing infrastructure

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>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index d1ce377db3e9..1d6b55a6f501 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);
+			count += acpi_probe_count;
+		} else {
+			int res;
+			res = acpi_table_parse(ape->id, ape->probe_table);
+			if (!res)
+				count++;
+		}
+	}
+	spin_unlock(&acpi_probe_lock);
+
+	return count;
+}