[PATCH v3 1/7] acpi: Add early device probing infrastructure

[Marc Zyngier]

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 at 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);
+			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;
+}
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 1781e54..efd7ed1 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -181,6 +181,16 @@
 #define CPUIDLE_METHOD_OF_TABLES() OF_TABLE(CONFIG_CPU_IDLE, cpuidle_method)
 #define EARLYCON_OF_TABLES()	OF_TABLE(CONFIG_SERIAL_EARLYCON, earlycon)
 
+#ifdef CONFIG_ACPI
+#define ACPI_PROBE_TABLE(name)						\
+	. = ALIGN(8);							\
+	VMLINUX_SYMBOL(__##name##_acpi_probe_table) = .;		\
+	*(__##name##_acpi_probe_table)					\
+	VMLINUX_SYMBOL(__##name##_acpi_probe_table_end) = .;
+#else
+#define ACPI_PROBE_TABLE(name)
+#endif
+
 #define KERNEL_DTB()							\
 	STRUCT_ALIGN();							\
 	VMLINUX_SYMBOL(__dtb_start) = .;				\
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 84e7055..51a96a8 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -787,6 +787,61 @@ int acpi_dev_prop_read(struct acpi_device *adev, const char *propname,
 
 struct fwnode_handle *acpi_get_next_subnode(struct device *dev,
 					    struct fwnode_handle *subnode);
+
+struct acpi_probe_entry;
+typedef bool (*acpi_probe_entry_validate_subtbl)(struct acpi_subtable_header *,
+						 struct acpi_probe_entry *);
+
+#define ACPI_TABLE_ID_LEN	5
+
+/**
+ * struct acpi_probe_entry - boot-time probing entry
+ * @id:			ACPI table name
+ * @type:		Optional subtable type to match
+ *			(if @id contains subtables)
+ * @subtable_valid:	Optional callback to check the validity of
+ *			the subtable
+ * @probe_table:	Callback to the driver being probed when table
+ *			match is successful
+ * @probe_subtbl:	Callback to the driver being probed when table and
+ *			subtable match (and optional callback is successful)
+ * @driver_data:	Sideband data provided back to the driver
+ */
+struct acpi_probe_entry {
+	__u8 id[ACPI_TABLE_ID_LEN];
+	__u8 type;
+	acpi_probe_entry_validate_subtbl subtable_valid;
+	union {
+		acpi_tbl_table_handler probe_table;
+		acpi_tbl_entry_handler probe_subtbl;
+	};
+	kernel_ulong_t driver_data;
+};
+
+#define ACPI_DECLARE_PROBE_ENTRY(table, name, table_id, subtable, valid, data, fn)	\
+	static const struct acpi_probe_entry __acpi_probe_##name	\
+		__used __section(__##table##_acpi_probe_table)		\
+		 = {							\
+			.id = table_id,					\
+			.type = subtable,				\
+			.subtable_valid = valid,			\
+			.probe_table = (acpi_tbl_table_handler)fn,	\
+			.driver_data = data, 				\
+		   }
+
+#define ACPI_PROBE_TABLE(name)		__##name##_acpi_probe_table
+#define ACPI_PROBE_TABLE_END(name)	__##name##_acpi_probe_table_end
+
+int __acpi_probe_device_table(struct acpi_probe_entry *start, int nr);
+
+#define acpi_probe_device_table(t)					\
+	({ 								\
+		extern struct acpi_probe_entry ACPI_PROBE_TABLE(t),	\
+			                       ACPI_PROBE_TABLE_END(t);	\
+		__acpi_probe_device_table(&ACPI_PROBE_TABLE(t),		\
+					  (&ACPI_PROBE_TABLE_END(t) -	\
+					   &ACPI_PROBE_TABLE(t)));	\
+	})
 #else
 static inline int acpi_dev_get_property(struct acpi_device *adev,
 					const char *name, acpi_object_type type,
@@ -845,6 +900,17 @@ static inline struct fwnode_handle *acpi_get_next_subnode(struct device *dev,
 {
 	return NULL;
 }
+
+#define ACPI_DECLARE_PROBE_ENTRY(table, name, table_id, subtable, validate, data, fn) \
+	static const void * __acpi_table_##name[]			\
+		__attribute__((unused))					\
+		 = { (void *) table_id,					\
+		     (void *) subtable,					\
+		     (void *) valid,					\
+		     (void *) fn,					\
+		     (void *) data }
+
+#define acpi_probe_device_table(t)	({ int __r = 0; __r;})
 #endif
 
 #endif	/*_LINUX_ACPI_H*/
-- 
2.1.4