[PATCH 2/2] ACPI/thermal: support for thermal zone description

[Prashanth Prakash <pprakash@codeaurora.org>]

Per ACPI 6.2 spec, platforms can optionally add a string(_STR)
object within each thermal zone package which provides a user
friendly name/description.

Add support to parse the string object, which will be exposed
to userspace by thermal framework.

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
---
 drivers/acpi/thermal.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index 1d0417b..6ab6480 100644
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -41,6 +41,7 @@
 #include <linux/acpi.h>
 #include <linux/workqueue.h>
 #include <linux/uaccess.h>
+#include <linux/nls.h>
 
 #define PREFIX "ACPI: "
 
@@ -188,6 +189,7 @@ struct acpi_thermal {
 	int tz_enabled;
 	int kelvin_offset;
 	struct work_struct thermal_check_work;
+	char desc[THERMAL_MAX_DESC_STR_LEN];
 };
 
 /* --------------------------------------------------------------------------
@@ -543,6 +545,15 @@ static int thermal_get_temp(struct thermal_zone_device *thermal, int *temp)
 	return 0;
 }
 
+static int thermal_get_desc(struct thermal_zone_device *thermal, char *desc,
+			int size)
+{
+	struct acpi_thermal *tz = thermal->devdata;
+
+	strlcpy(desc, tz->desc, size);
+	return 0;
+}
+
 static int thermal_get_mode(struct thermal_zone_device *thermal,
 				enum thermal_device_mode *mode)
 {
@@ -880,6 +891,7 @@ static int acpi_thermal_cooling_device_cb(struct thermal_zone_device *thermal,
 	.get_crit_temp = thermal_get_crit_temp,
 	.get_trend = thermal_get_trend,
 	.notify = thermal_notify,
+	.get_desc = thermal_get_desc,
 };
 
 static int acpi_thermal_register_thermal_zone(struct acpi_thermal *tz)
@@ -1014,6 +1026,29 @@ static void acpi_thermal_aml_dependency_fix(struct acpi_thermal *tz)
 	acpi_evaluate_integer(handle, "_TMP", NULL, &value);
 }
 
+static void acpi_thermal_get_desc(struct acpi_thermal *tz)
+{
+	acpi_handle handle = tz->device->handle;
+	acpi_status status;
+	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
+
+	status = acpi_evaluate_object(handle, "_STR", NULL, &buffer);
+
+	if (ACPI_FAILURE(status))
+		strlcpy(tz->desc, "<not supported>", THERMAL_MAX_DESC_STR_LEN);
+	else {
+		union acpi_object *str;
+		int result;
+
+		str = buffer.pointer;
+		result = utf16s_to_utf8s((wchar_t *)str->string.pointer,
+					str->string.length, UTF16_LITTLE_ENDIAN,
+					tz->desc, THERMAL_MAX_DESC_STR_LEN-1);
+		tz->desc[result] = 0;
+		kfree(buffer.pointer);
+	}
+}
+
 static int acpi_thermal_get_info(struct acpi_thermal *tz)
 {
 	int result = 0;
@@ -1045,6 +1080,9 @@ static int acpi_thermal_get_info(struct acpi_thermal *tz)
 	else
 		acpi_thermal_get_polling_frequency(tz);
 
+	/* Get thermal zone description [_STR] (optional) */
+	acpi_thermal_get_desc(tz);
+
 	return 0;
 }
 
-- 
Qualcomm Datacenter Technologies on behalf of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.