mfd: cros_ec: Use fixed size arrays to transfer data with the EC

The struct cros_ec_command will be used as an ioctl() argument for the
API to control the ChromeOS EC from user-space. So the data structure
has to be 64-bit safe to make it compatible between 32 and 64 avoiding
the need for a compat ioctl interface. Since pointers are self-aligned
to different byte boundaries, use fixed size arrays instead of pointers
for transferring ingoing and outgoing data with the Embedded Controller.

Also, re-arrange struct members by decreasing alignment requirements to
reduce the needing padding size.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Acked-by: Lee Jones <lee.jones@linaro.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>

drivers/i2c/busses/i2c-cros-ec-tunnel.c

@@ -182,72 +182,41 @@ static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
 	const u16 bus_num = bus->remote_bus;
 	int request_len;
 	int response_len;
-	u8 *request = NULL;
-	u8 *response = NULL;
 	int result;
-	struct cros_ec_command msg;
+	struct cros_ec_command msg = { };
 
 	request_len = ec_i2c_count_message(i2c_msgs, num);
 	if (request_len < 0) {
 		dev_warn(dev, "Error constructing message %d\n", request_len);
-		result = request_len;
+		return request_len;
-		goto exit;
 	}
+
 	response_len = ec_i2c_count_response(i2c_msgs, num);
 	if (response_len < 0) {
 		/* Unexpected; no errors should come when NULL response */
 		dev_warn(dev, "Error preparing response %d\n", response_len);
-		result = response_len;
+		return response_len;
-		goto exit;
 	}
 
-	if (request_len <= ARRAY_SIZE(bus->request_buf)) {
+	result = ec_i2c_construct_message(msg.outdata, i2c_msgs, num, bus_num);
-		request = bus->request_buf;
-	} else {
-		request = kzalloc(request_len, GFP_KERNEL);
-		if (request == NULL) {
-			result = -ENOMEM;
-			goto exit;
-		}
-	}
-	if (response_len <= ARRAY_SIZE(bus->response_buf)) {
-		response = bus->response_buf;
-	} else {
-		response = kzalloc(response_len, GFP_KERNEL);
-		if (response == NULL) {
-			result = -ENOMEM;
-			goto exit;
-		}
-	}
-
-	result = ec_i2c_construct_message(request, i2c_msgs, num, bus_num);
 	if (result)
-		goto exit;
+		return result;
 
 	msg.version = 0;
 	msg.command = EC_CMD_I2C_PASSTHRU;
-	msg.outdata = request;
 	msg.outsize = request_len;
-	msg.indata = response;
 	msg.insize = response_len;
 
 	result = cros_ec_cmd_xfer(bus->ec, &msg);
 	if (result < 0)
-		goto exit;
+		return result;
 
-	result = ec_i2c_parse_response(response, i2c_msgs, &num);
+	result = ec_i2c_parse_response(msg.indata, i2c_msgs, &num);
 	if (result < 0)
-		goto exit;
+		return result;
 
 	/* Indicate success by saying how many messages were sent */
-	result = num;
+	return num;
-exit:
-	if (request != bus->request_buf)
-		kfree(request);
-	if (response != bus->response_buf)
-		kfree(response);
-
-	return result;
 }
 
 static u32 ec_i2c_functionality(struct i2c_adapter *adap)

drivers/input/keyboard/cros_ec_keyb.c

@@ -148,16 +148,19 @@ static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
 
 static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
 {
+	int ret;
 	struct cros_ec_command msg = {
-		.version = 0,
 		.command = EC_CMD_MKBP_STATE,
-		.outdata = NULL,
-		.outsize = 0,
-		.indata = kb_state,
 		.insize = ckdev->cols,
 	};
 
-	return cros_ec_cmd_xfer(ckdev->ec, &msg);
+	ret = cros_ec_cmd_xfer(ckdev->ec, &msg);
+	if (ret < 0)
+		return ret;
+
+	memcpy(kb_state, msg.indata, ckdev->cols);
+
+	return 0;
 }
 
 static irqreturn_t cros_ec_keyb_irq(int irq, void *data)

drivers/mfd/cros_ec.c

@@ -74,15 +74,11 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
 	ret = ec_dev->cmd_xfer(ec_dev, msg);
 	if (msg->result == EC_RES_IN_PROGRESS) {
 		int i;
-		struct cros_ec_command status_msg;
+		struct cros_ec_command status_msg = { };
-		struct ec_response_get_comms_status status;
+		struct ec_response_get_comms_status *status;
 
-		status_msg.version = 0;
 		status_msg.command = EC_CMD_GET_COMMS_STATUS;
-		status_msg.outdata = NULL;
+		status_msg.insize = sizeof(*status);
-		status_msg.outsize = 0;
-		status_msg.indata = (uint8_t *)&status;
-		status_msg.insize = sizeof(status);
 
 		/*
 		 * Query the EC's status until it's no longer busy or
@@ -98,7 +94,10 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
 			msg->result = status_msg.result;
 			if (status_msg.result != EC_RES_SUCCESS)
 				break;
-			if (!(status.flags & EC_COMMS_STATUS_PROCESSING))
+
+			status = (struct ec_response_get_comms_status *)
+				 status_msg.indata;
+			if (!(status->flags & EC_COMMS_STATUS_PROCESSING))
 				break;
 		}
 	}

include/linux/mfd/cros_ec.h

@@ -38,20 +38,20 @@ enum {
 /*
  * @version: Command version number (often 0)
  * @command: Command to send (EC_CMD_...)
- * @outdata: Outgoing data to EC
  * @outsize: Outgoing length in bytes
- * @indata: Where to put the incoming data from EC
  * @insize: Max number of bytes to accept from EC
  * @result: EC's response to the command (separate from communication failure)
+ * @outdata: Outgoing data to EC
+ * @indata: Where to put the incoming data from EC
  */
 struct cros_ec_command {
 	uint32_t version;
 	uint32_t command;
-	uint8_t *outdata;
 	uint32_t outsize;
-	uint8_t *indata;
 	uint32_t insize;
 	uint32_t result;
+	uint8_t outdata[EC_PROTO2_MAX_PARAM_SIZE];
+	uint8_t indata[EC_PROTO2_MAX_PARAM_SIZE];
 };
 
 /**