[PATCH v2] acpi: configfs: Unload SSDT on configfs entry removal

[Jan Kiszka <jan.kiszka@siemens.com>]

Call directly into acpica to load a table to obtain its index on return.
We choose the direct call of acpica internal functions to avoid having
to modify its API which is used outside of Linux as well.

Use that index to unload the table again when the corresponding
directory in configfs gets removed. This allows to change SSDTs without
rebooting the system. It also allows to destroy devices again that a
dynamically loaded SSDT created.

This is widely similar to the DT overlay behavior.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

Changes in v2:
 - do not touch acpica

 drivers/acpi/acpi_configfs.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/acpi_configfs.c b/drivers/acpi/acpi_configfs.c
index 146a77fb762d..853bc7fc673f 100644
--- a/drivers/acpi/acpi_configfs.c
+++ b/drivers/acpi/acpi_configfs.c
@@ -15,11 +15,15 @@
 #include <linux/configfs.h>
 #include <linux/acpi.h>
 
+#include "acpica/accommon.h"
+#include "acpica/actables.h"
+
 static struct config_group *acpi_table_group;
 
 struct acpi_table {
 	struct config_item cfg;
 	struct acpi_table_header *header;
+	u32 index;
 };
 
 static ssize_t acpi_table_aml_write(struct config_item *cfg,
@@ -52,7 +56,11 @@ static ssize_t acpi_table_aml_write(struct config_item *cfg,
 	if (!table->header)
 		return -ENOMEM;
 
-	ret = acpi_load_table(table->header);
+	ACPI_INFO(("Host-directed Dynamic ACPI Table Load:"));
+	ret = acpi_tb_install_and_load_table(
+			ACPI_PTR_TO_PHYSADDR(table->header),
+			ACPI_TABLE_ORIGIN_EXTERNAL_VIRTUAL, FALSE,
+			&table->index);
 	if (ret) {
 		kfree(table->header);
 		table->header = NULL;
@@ -215,8 +223,18 @@ static struct config_item *acpi_table_make_item(struct config_group *group,
 	return &table->cfg;
 }
 
+static void acpi_table_drop_item(struct config_group *group,
+				 struct config_item *cfg)
+{
+	struct acpi_table *table = container_of(cfg, struct acpi_table, cfg);
+
+	ACPI_INFO(("Host-directed Dynamic ACPI Table Unload"));
+	acpi_tb_unload_table(table->index);
+}
+
 struct configfs_group_operations acpi_table_group_ops = {
 	.make_item = acpi_table_make_item,
+	.drop_item = acpi_table_drop_item,
 };
 
 static struct config_item_type acpi_tables_type = {