[RFC PATCH v3 02/13] drivers: acpi: iort: introduce linker section for IORT entries probing

[Lorenzo Pieralisi]

Since commit e647b532275b ("ACPI: Add early device probing
infrastructure") the kernel has gained the infrastructure that allows
adding linker script section entries to execute ACPI driver callbacks
(ie probe routines) for all subsystems that register a table entry
in the respective kernel section (eg clocksource, irqchip).

Since ARM IOMMU devices data is described through IORT tables when
booting with ACPI, the ARM IOMMU drivers must be made able to hook ACPI
callback routines that are called to probe IORT entries and initialize
the respective IOMMU devices.

To avoid adding driver specific hooks into IORT table initialization
code (breaking therefore code modularity - ie ACPI IORT code must be made
aware of ARM SMMU drivers ACPI init callbacks), this patch adds code
that allows ARM SMMU drivers to take advantage of the ACPI early probing
infrastructure, so that they can add linker script section entries
containing drivers callback to be executed on IORT tables detection.

Since IORT nodes are differentiated by a type, the callback routines
can easily parse the IORT table entries, check the IORT nodes and
carry out some actions whenever the IORT node type associated with
the driver specific callback is matched.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
Cc: Tomasz Nowicki <tn at semihalf.com>
Cc: "Rafael J. Wysocki" <rjw at rjwysocki.net>
Cc: Marc Zyngier <marc.zyngier at arm.com>
---
 drivers/acpi/iort.c               | 2 ++
 include/asm-generic/vmlinux.lds.h | 1 +
 include/linux/iort.h              | 3 +++
 3 files changed, 6 insertions(+)

diff --git a/drivers/acpi/iort.c b/drivers/acpi/iort.c
index 6611607..1f440d2 100644
--- a/drivers/acpi/iort.c
+++ b/drivers/acpi/iort.c
@@ -383,4 +383,6 @@ void __init iort_table_detect(void)
 		const char *msg = acpi_format_exception(status);
 		pr_err("Failed to get table, %s\n", msg);
 	}
+
+	acpi_probe_device_table(iort);
 }
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 6a67ab9..b896ab2 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -538,6 +538,7 @@
 	IRQCHIP_OF_MATCH_TABLE()					\
 	ACPI_PROBE_TABLE(irqchip)					\
 	ACPI_PROBE_TABLE(clksrc)					\
+	ACPI_PROBE_TABLE(iort)						\
 	EARLYCON_TABLE()
 
 #define INIT_TEXT							\
diff --git a/include/linux/iort.h b/include/linux/iort.h
index d7daba1..9bb30c5 100644
--- a/include/linux/iort.h
+++ b/include/linux/iort.h
@@ -38,4 +38,7 @@ static inline struct irq_domain *
 iort_get_device_domain(struct device *dev, u32 req_id) { return NULL; }
 #endif
 
+#define IORT_ACPI_DECLARE(name, table_id, fn)		\
+	ACPI_DECLARE_PROBE_ENTRY(iort, name, table_id, 0, NULL, 0, fn)
+
 #endif /* __IORT_H__ */
-- 
2.6.4