greybus: fix battery_operation()

This patch fixes some problems with the battery protocol driver.

First, when gb_operation_create() is called, it creates buffers of
the requested sizes to hold the operation request and response
messages.  There is therefore no reason to allocate a local response
buffer.  By the time the (synchronous) gb_operation_request_send()
call returns, the operation response buffer will have been filled in.

(In addition, the content of local_response was not being filled
before its contents were used...)

Next, all the message structures are misnamed.  The structures that
are defined are all the content of operation response messages (not
request messages).  So this changes all the types names to properly
reflect their role.

All the local variables using these types are similarly renamed.

I added a new type, gb_generic_battery_response, to be used for
casting the fake_response used in battery_operation().
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/battery-gb.c

@@ -54,7 +54,7 @@ struct gb_battery_proto_version_response {
 #define GB_BATTERY_TECH_NiCd			0x0005
 #define GB_BATTERY_TECH_LiMn			0x0006
 
-struct gb_battery_technology_request {
+struct gb_battery_technology_response {
 	__u8	status;
 	__le32	technology;
 };
@@ -66,50 +66,53 @@ struct gb_battery_technology_request {
 #define GB_BATTERY_STATUS_NOT_CHARGING		0x0003
 #define GB_BATTERY_STATUS_FULL			0x0004
 
-struct gb_battery_status_request {
+struct gb_battery_status_response {
 	__u8	status;
 	__le16	battery_status;
 };
 
-struct gb_battery_max_voltage_request {
+struct gb_battery_max_voltage_response {
 	__u8	status;
 	__le32	max_voltage;
 };
 
-struct gb_battery_capacity_request {
+struct gb_battery_capacity_response {
 	__u8	status;
 	__le32	capacity;
 };
 
-struct gb_battery_temperature_request {
+struct gb_battery_temperature_response {
 	__u8	status;
 	__le32	temperature;
 };
 
-struct gb_battery_voltage_request {
+struct gb_battery_voltage_response {
 	__u8	status;
 	__le32	voltage;
 };
 
+/* Generia response structure--prefix for all other responses */
+struct gb_generic_battery_response {
+	__u8	status;
+};
 
+/*
+ * None of the battery operation requests have any payload.  This
+ * function implements all of the requests by allowing the caller to
+ * supply a buffer into which the operation response should be
+ * copied.
+ */
 static int battery_operation(struct gb_battery *gb, int type,
 			     void *response, int response_size)
 {
 	struct gb_connection *connection = gb->connection;
 	struct gb_operation *operation;
-	struct gb_battery_technology_request *fake_request;
-	u8 *local_response;
+	struct gb_generic_battery_response *fake_response;
 	int ret;
 
-	local_response = kmalloc(response_size, GFP_KERNEL);
-	if (!local_response)
-		return -ENOMEM;
-
 	operation = gb_operation_create(connection, type, 0, response_size);
-	if (!operation) {
-		kfree(local_response);
+	if (!operation)
 		return -ENOMEM;
-	}
 
 	/* Synchronous operation--no callback */
 	ret = gb_operation_request_send(operation, NULL);
@@ -123,18 +126,17 @@ static int battery_operation(struct gb_battery *gb, int type,
 	 * layout for where the status is, so cast this to a random request so
 	 * we can see the status easier.
 	 */
-	fake_request = (struct gb_battery_technology_request *)local_response;
-	if (fake_request->status) {
+	fake_response = operation->response.payload;
+	if (fake_response->status) {
 		gb_connection_err(connection, "version response %hhu",
-			fake_request->status);
+			fake_response->status);
 		ret = -EIO;
 	} else {
-		/* Good request, so copy to the caller's buffer */
-		memcpy(response, local_response, response_size);
+		/* Good response, so copy to the caller's buffer */
+		memcpy(response, fake_response, response_size);
 	}
 out:
 	gb_operation_destroy(operation);
-	kfree(local_response);
 
 	return ret;
 }
@@ -145,33 +147,33 @@ static int battery_operation(struct gb_battery *gb, int type,
  */
 static int get_version(struct gb_battery *gb)
 {
-	struct gb_battery_proto_version_response version_request;
+	struct gb_battery_proto_version_response version_response;
 	int retval;
 
 	retval = battery_operation(gb, GB_BATTERY_TYPE_PROTOCOL_VERSION,
-				   &version_request, sizeof(version_request));
+				   &version_response, sizeof(version_response));
 	if (retval)
 		return retval;
 
-	if (version_request.major > GB_BATTERY_VERSION_MAJOR) {
+	if (version_response.major > GB_BATTERY_VERSION_MAJOR) {
 		pr_err("unsupported major version (%hhu > %hhu)\n",
-			version_request.major, GB_BATTERY_VERSION_MAJOR);
+			version_response.major, GB_BATTERY_VERSION_MAJOR);
 		return -ENOTSUPP;
 	}
 
-	gb->version_major = version_request.major;
-	gb->version_minor = version_request.minor;
+	gb->version_major = version_response.major;
+	gb->version_minor = version_response.minor;
 	return 0;
 }
 
 static int get_tech(struct gb_battery *gb)
 {
-	struct gb_battery_technology_request tech_request;
+	struct gb_battery_technology_response tech_response;
 	u32 technology;
 	int retval;
 
 	retval = battery_operation(gb, GB_BATTERY_TYPE_TECHNOLOGY,
-				   &tech_request, sizeof(tech_request));
+				   &tech_response, sizeof(tech_response));
 	if (retval)
 		return retval;
 
@@ -180,7 +182,7 @@ static int get_tech(struct gb_battery *gb)
 	 * "identical" which should allow gcc to optomize the code away to
 	 * nothing.
 	 */
-	technology = le32_to_cpu(tech_request.technology);
+	technology = le32_to_cpu(tech_response.technology);
 	switch (technology) {
 	case GB_BATTERY_TECH_NiMH:
 		technology = POWER_SUPPLY_TECHNOLOGY_NiMH;
@@ -210,12 +212,12 @@ static int get_tech(struct gb_battery *gb)
 
 static int get_status(struct gb_battery *gb)
 {
-	struct gb_battery_status_request status_request;
+	struct gb_battery_status_response status_response;
 	u16 battery_status;
 	int retval;
 
 	retval = battery_operation(gb, GB_BATTERY_TYPE_STATUS,
-				   &status_request, sizeof(status_request));
+				   &status_response, sizeof(status_response));
 	if (retval)
 		return retval;
 
@@ -224,7 +226,7 @@ static int get_status(struct gb_battery *gb)
 	 * "identical" which should allow gcc to optomize the code away to
 	 * nothing.
 	 */
-	battery_status = le16_to_cpu(status_request.battery_status);
+	battery_status = le16_to_cpu(status_response.battery_status);
 	switch (battery_status) {
 	case GB_BATTERY_STATUS_CHARGING:
 		battery_status = POWER_SUPPLY_STATUS_CHARGING;
@@ -248,61 +250,61 @@ static int get_status(struct gb_battery *gb)
 
 static int get_max_voltage(struct gb_battery *gb)
 {
-	struct gb_battery_max_voltage_request volt_request;
+	struct gb_battery_max_voltage_response volt_response;
 	u32 max_voltage;
 	int retval;
 
 	retval = battery_operation(gb, GB_BATTERY_TYPE_MAX_VOLTAGE,
-				   &volt_request, sizeof(volt_request));
+				   &volt_response, sizeof(volt_response));
 	if (retval)
 		return retval;
 
-	max_voltage = le32_to_cpu(volt_request.max_voltage);
+	max_voltage = le32_to_cpu(volt_response.max_voltage);
 	return max_voltage;
 }
 
 static int get_capacity(struct gb_battery *gb)
 {
-	struct gb_battery_capacity_request capacity_request;
+	struct gb_battery_capacity_response capacity_response;
 	u32 capacity;
 	int retval;
 
 	retval = battery_operation(gb, GB_BATTERY_TYPE_CAPACITY,
-				   &capacity_request, sizeof(capacity_request));
+				   &capacity_response, sizeof(capacity_response));
 	if (retval)
 		return retval;
 
-	capacity = le32_to_cpu(capacity_request.capacity);
+	capacity = le32_to_cpu(capacity_response.capacity);
 	return capacity;
 }
 
 static int get_temp(struct gb_battery *gb)
 {
-	struct gb_battery_temperature_request temp_request;
+	struct gb_battery_temperature_response temp_response;
 	u32 temperature;
 	int retval;
 
 	retval = battery_operation(gb, GB_BATTERY_TYPE_TEMPERATURE,
-				   &temp_request, sizeof(temp_request));
+				   &temp_response, sizeof(temp_response));
 	if (retval)
 		return retval;
 
-	temperature = le32_to_cpu(temp_request.temperature);
+	temperature = le32_to_cpu(temp_response.temperature);
 	return temperature;
 }
 
 static int get_voltage(struct gb_battery *gb)
 {
-	struct gb_battery_voltage_request voltage_request;
+	struct gb_battery_voltage_response voltage_response;
 	u32 voltage;
 	int retval;
 
 	retval = battery_operation(gb, GB_BATTERY_TYPE_VOLTAGE,
-				   &voltage_request, sizeof(voltage_request));
+				   &voltage_response, sizeof(voltage_response));
 	if (retval)
 		return retval;
 
-	voltage = le32_to_cpu(voltage_request.voltage);
+	voltage = le32_to_cpu(voltage_response.voltage);
 	return voltage;
 }