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Diffstat (limited to 'drivers/acpi/acpi_keyvalue.c')
-rw-r--r--drivers/acpi/acpi_keyvalue.c115
1 files changed, 115 insertions, 0 deletions
diff --git a/drivers/acpi/acpi_keyvalue.c b/drivers/acpi/acpi_keyvalue.c
new file mode 100644
index 000000000000..5c3cde921b22
--- /dev/null
+++ b/drivers/acpi/acpi_keyvalue.c
@@ -0,0 +1,115 @@
+/*
+ * Key/Value handler from _DSM method
+ *
+ * Copyright (C) 2013 Linaro Ltd
+ *
+ * Author: Graeme Gregory <graeme.gregory@linaro.org>
+ *
+ * Original based on code :-
+ *
+ * Copyright (C) 2013 Advanced Micro Devices, Inc.
+ *
+ * Author: Brandon Anderson <brandon.anderson@amd.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/acpi.h>
+
+/* UUID: a706b112-bf0b-48d2-9fa3-95591a3c4c06 (randomly generated) */
+static const char acpi_amba_dsm_uuid[] = {
+ 0xa7, 0x06, 0xb1, 0x12, 0xbf, 0x0b, 0x48, 0xd2,
+ 0x9f, 0xa3, 0x95, 0x59, 0x1a, 0x3c, 0x4c, 0x06
+};
+
+/* acpi_dsm_lookup_value()
+ *
+ * Helper to parse through ACPI _DSM object for a device. Each entry
+ * has three fields.
+ */
+int acpi_dsm_lookup_value(acpi_handle handle,
+ const char *tag, int index,
+ struct acpi_dsm_entry *entry)
+{
+ acpi_status status;
+ struct acpi_object_list input;
+ struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
+ union acpi_object params[4];
+ union acpi_object *obj;
+ int len, match_count, i;
+
+ /* invalidate output in case there's no entry to supply */
+ entry->key = NULL;
+ entry->value = NULL;
+
+ if (!acpi_has_method(handle, "_DSM"))
+ return -ENOENT;
+
+ input.count = 4;
+ params[0].type = ACPI_TYPE_BUFFER; /* UUID */
+ params[0].buffer.length = sizeof(acpi_amba_dsm_uuid);
+ params[0].buffer.pointer = (char *)acpi_amba_dsm_uuid;
+ params[1].type = ACPI_TYPE_INTEGER; /* Revision */
+ params[1].integer.value = 1;
+ params[2].type = ACPI_TYPE_INTEGER; /* Function # */
+ params[2].integer.value = 1;
+ params[3].type = ACPI_TYPE_PACKAGE; /* Arguments */
+ params[3].package.count = 0;
+ params[3].package.elements = NULL;
+ input.pointer = params;
+
+ status = acpi_evaluate_object_typed(handle, "_DSM",
+ &input, &output, ACPI_TYPE_PACKAGE);
+ if (ACPI_FAILURE(status)) {
+ pr_err("failed to get _DSM package for this device\n");
+ return -ENOENT;
+ }
+
+ obj = (union acpi_object *)output.pointer;
+
+ /* parse 2 objects per entry */
+ match_count = 0;
+ for (i = 0; (i + 2) <= obj->package.count; i += 2) {
+ /* key must be a string */
+ len = obj->package.elements[i].string.length;
+ if (len <= 0)
+ continue;
+
+ /* check to see if this is the entry to return */
+ if (strncmp(tag, obj->package.elements[i].string.pointer,
+ len) != 0 ||
+ match_count < index) {
+ match_count++;
+ continue;
+ }
+
+ /* copy the key */
+ entry->key = kmalloc(len + 1, GFP_KERNEL);
+ strncpy(entry->key,
+ obj->package.elements[i].string.pointer,
+ len);
+ entry->key[len] = '\0';
+
+ /* value is a string with space-delimited fields if necessary */
+ len = obj->package.elements[i + 1].string.length;
+ if (len > 0) {
+ entry->value = kmalloc(len + 1, GFP_KERNEL);
+ strncpy(entry->value,
+ obj->package.elements[i+1].string.pointer,
+ len);
+ entry->value[len] = '\0';
+ }
+
+ break;
+ }
+
+ kfree(output.pointer);
+
+ if (entry->key == NULL)
+ return -ENOENT;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_dsm_lookup_value);