[RFC PATCH v2 10/10] HACK: acpi: configfs: add unload_hanlde_path attribute for tables

[Octavian Purdila <octavian.purdila@intel.com>]

Because there is no way to get a references to a table that we can use
to unload a table this patch adds an attribute allows the user to attach
a path to an ACPI handle to be used when unloading the table. The ACPI
handle must have been loaded with the table to which attribute is part
of, otherwise the unload operation will not be correct.

This patch should only be used to test table unloading and removal of
associated ACPI devices and should not be merged. Once the new table
loading/unloading APIs make it in ACPICA we can implement table
unloading properly.

Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
---
 drivers/acpi/configfs.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

diff --git a/drivers/acpi/configfs.c b/drivers/acpi/configfs.c
index 5efa8ca..7bcdfbb 100644
--- a/drivers/acpi/configfs.c
+++ b/drivers/acpi/configfs.c
@@ -18,6 +18,7 @@ static struct config_group *acpi_table_group;
 struct acpi_user_table {
 	struct config_item cfg;
 	struct acpi_table_header *table;
+	acpi_handle handle;
 };
 
 static ssize_t acpi_table_data_write(struct config_item *cfg,
@@ -65,14 +66,59 @@ static ssize_t acpi_table_data_write(struct config_item *cfg,
 
 CONFIGFS_BIN_ATTR_WO(acpi_table_, data, NULL, MAX_ACPI_TABLE_SIZE);
 
+ssize_t acpi_table_unload_handle_path_show(struct config_item *item, char *page)
+{
+	struct acpi_buffer path = {ACPI_ALLOCATE_BUFFER, NULL};
+	struct acpi_user_table *table;
+	int ret;
+
+	table = container_of(item, struct acpi_user_table, cfg);
+
+	ret = acpi_get_name(table->handle, ACPI_FULL_PATHNAME, &path);
+	if (ret)
+		return ret;
+
+	ret = sprintf(page, "%s\n", (char *)path.pointer);
+	kfree(path.pointer);
+
+	return ret;
+}
+
+ssize_t acpi_table_unload_handle_path_store(struct config_item *item,
+					    const char *page, size_t count)
+{
+	struct acpi_user_table *table;
+	char *str;
+
+	table = container_of(item, struct acpi_user_table, cfg);
+
+	str = kmalloc(count + 1, GFP_KERNEL);
+	memcpy(str, page, count);
+	str[count] = 0;
+
+	acpi_get_handle(NULL, strim(str), &table->handle);
+
+	kfree(str);
+
+	return count;
+}
+
+CONFIGFS_ATTR(acpi_table_, unload_handle_path);
+
 struct configfs_bin_attribute *acpi_table_bin_attrs[] = {
 	&acpi_table_attr_data,
 	NULL,
 };
 
+struct configfs_attribute *acpi_table_attrs[] = {
+	&acpi_table_attr_unload_handle_path,
+	NULL,
+};
+
 static struct config_item_type acpi_table_type = {
 	.ct_owner = THIS_MODULE,
 	.ct_bin_attrs = acpi_table_bin_attrs,
+	.ct_attrs = acpi_table_attrs,
 };
 
 static struct config_item *acpi_table_make_item(struct config_group *group,
@@ -88,8 +134,20 @@ 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 *item)
+{
+	struct acpi_user_table *table;
+
+	table = container_of(item, struct acpi_user_table, cfg);
+
+	if (table->handle)
+		acpi_unload_parent_table(table->handle);
+}
+
 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 = {
-- 
1.9.1