HID: intel-ish-hid: remove data[128] usage on stack when sending HBM request

Instead of using an 128-byte on-stack array to store the request, we can
instantiate the request on stack directly. This can save the stack usage of
these functions, since most of the requests are much smaller than 128 bytes.
Signed-off-by: Hong Liu <hong.liu@intel.com>
Tested-by: Hongyan Song <hongyan.song@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/intel-ish-hid/ishtp/bus.c

@@ -119,7 +119,7 @@ int ishtp_send_msg(struct ishtp_device *dev, struct ishtp_msg_hdr *hdr,
  * Return: This returns IPC send message status.
  */
 int ishtp_write_message(struct ishtp_device *dev, struct ishtp_msg_hdr *hdr,
-			unsigned char *buf)
+			void *buf)
 {
 	return ishtp_send_msg(dev, hdr, buf, NULL, NULL);
 }

drivers/hid/intel-ish-hid/ishtp/bus.h

@@ -85,7 +85,7 @@ int	ishtp_send_msg(struct ishtp_device *dev,
 /* Write a single-fragment message */
 int	ishtp_write_message(struct ishtp_device *dev,
 			    struct ishtp_msg_hdr *hdr,
-			    unsigned char *buf);
+			    void *buf);
 
 /* Use DMA to send/receive messages */
 int ishtp_use_dma_transfer(void);

drivers/hid/intel-ish-hid/ishtp/hbm.c

@@ -136,19 +136,14 @@ int ishtp_hbm_start_wait(struct ishtp_device *dev)
 int ishtp_hbm_start_req(struct ishtp_device *dev)
 {
 	struct ishtp_msg_hdr hdr;
-	unsigned char data[128];
-	struct ishtp_msg_hdr *ishtp_hdr = &hdr;
-	struct hbm_host_version_request *start_req;
-	const size_t len = sizeof(struct hbm_host_version_request);
+	struct hbm_host_version_request start_req = { 0 };
 
-	ishtp_hbm_hdr(ishtp_hdr, len);
+	ishtp_hbm_hdr(&hdr, sizeof(start_req));
 
 	/* host start message */
-	start_req = (struct hbm_host_version_request *)data;
-	memset(start_req, 0, len);
-	start_req->hbm_cmd = HOST_START_REQ_CMD;
-	start_req->host_version.major_version = HBM_MAJOR_VERSION;
-	start_req->host_version.minor_version = HBM_MINOR_VERSION;
+	start_req.hbm_cmd = HOST_START_REQ_CMD;
+	start_req.host_version.major_version = HBM_MAJOR_VERSION;
+	start_req.host_version.minor_version = HBM_MINOR_VERSION;
 
 	/*
 	 * (!) Response to HBM start may be so quick that this thread would get
@@ -156,7 +151,7 @@ int ishtp_hbm_start_req(struct ishtp_device *dev)
 	 * So set it at first, change back to ISHTP_HBM_IDLE upon failure
 	 */
 	dev->hbm_state = ISHTP_HBM_START;
-	if (ishtp_write_message(dev, ishtp_hdr, data)) {
+	if (ishtp_write_message(dev, &hdr, &start_req)) {
 		dev_err(dev->devc, "version message send failed\n");
 		dev->dev_state = ISHTP_DEV_RESETTING;
 		dev->hbm_state = ISHTP_HBM_IDLE;
@@ -178,19 +173,13 @@ int ishtp_hbm_start_req(struct ishtp_device *dev)
 void ishtp_hbm_enum_clients_req(struct ishtp_device *dev)
 {
 	struct ishtp_msg_hdr hdr;
-	unsigned char data[128];
-	struct ishtp_msg_hdr *ishtp_hdr = &hdr;
-	struct hbm_host_enum_request *enum_req;
-	const size_t len = sizeof(struct hbm_host_enum_request);
+	struct hbm_host_enum_request enum_req = { 0 };
 
 	/* enumerate clients */
-	ishtp_hbm_hdr(ishtp_hdr, len);
+	ishtp_hbm_hdr(&hdr, sizeof(enum_req));
+	enum_req.hbm_cmd = HOST_ENUM_REQ_CMD;
 
-	enum_req = (struct hbm_host_enum_request *)data;
-	memset(enum_req, 0, len);
-	enum_req->hbm_cmd = HOST_ENUM_REQ_CMD;
-
-	if (ishtp_write_message(dev, ishtp_hdr, data)) {
+	if (ishtp_write_message(dev, &hdr, &enum_req)) {
 		dev->dev_state = ISHTP_DEV_RESETTING;
 		dev_err(dev->devc, "enumeration request send failed\n");
 		ish_hw_reset(dev);
@@ -208,12 +197,8 @@ void ishtp_hbm_enum_clients_req(struct ishtp_device *dev)
  */
 static int ishtp_hbm_prop_req(struct ishtp_device *dev)
 {
-
 	struct ishtp_msg_hdr hdr;
-	unsigned char data[128];
-	struct ishtp_msg_hdr *ishtp_hdr = &hdr;
-	struct hbm_props_request *prop_req;
-	const size_t len = sizeof(struct hbm_props_request);
+	struct hbm_props_request prop_req = { 0 };
 	unsigned long next_client_index;
 	uint8_t client_num;
 
@@ -237,15 +222,12 @@ static int ishtp_hbm_prop_req(struct ishtp_device *dev)
 
 	dev->fw_clients[client_num].client_id = next_client_index;
 
-	ishtp_hbm_hdr(ishtp_hdr, len);
-	prop_req = (struct hbm_props_request *)data;
+	ishtp_hbm_hdr(&hdr, sizeof(prop_req));
 
-	memset(prop_req, 0, sizeof(struct hbm_props_request));
+	prop_req.hbm_cmd = HOST_CLIENT_PROPERTIES_REQ_CMD;
+	prop_req.address = next_client_index;
 
-	prop_req->hbm_cmd = HOST_CLIENT_PROPERTIES_REQ_CMD;
-	prop_req->address = next_client_index;
-
-	if (ishtp_write_message(dev, ishtp_hdr, data)) {
+	if (ishtp_write_message(dev, &hdr, &prop_req)) {
 		dev->dev_state = ISHTP_DEV_RESETTING;
 		dev_err(dev->devc, "properties request send failed\n");
 		ish_hw_reset(dev);
@@ -266,19 +248,14 @@ static int ishtp_hbm_prop_req(struct ishtp_device *dev)
 static void ishtp_hbm_stop_req(struct ishtp_device *dev)
 {
 	struct ishtp_msg_hdr hdr;
-	unsigned char data[128];
-	struct ishtp_msg_hdr *ishtp_hdr = &hdr;
-	struct hbm_host_stop_request *req;
-	const size_t len = sizeof(struct hbm_host_stop_request);
+	struct hbm_host_stop_request stop_req = { 0 } ;
 
-	ishtp_hbm_hdr(ishtp_hdr, len);
-	req = (struct hbm_host_stop_request *)data;
+	ishtp_hbm_hdr(&hdr, sizeof(stop_req));
 
-	memset(req, 0, sizeof(struct hbm_host_stop_request));
-	req->hbm_cmd = HOST_STOP_REQ_CMD;
-	req->reason = DRIVER_STOP_REQUEST;
+	stop_req.hbm_cmd = HOST_STOP_REQ_CMD;
+	stop_req.reason = DRIVER_STOP_REQUEST;
 
-	ishtp_write_message(dev, ishtp_hdr, data);
+	ishtp_write_message(dev, &hdr, &stop_req);
 }
 
 /**
@@ -294,15 +271,15 @@ int ishtp_hbm_cl_flow_control_req(struct ishtp_device *dev,
 				  struct ishtp_cl *cl)
 {
 	struct ishtp_msg_hdr hdr;
-	unsigned char data[128];
-	struct ishtp_msg_hdr *ishtp_hdr = &hdr;
-	const size_t len = sizeof(struct hbm_flow_control);
+	struct hbm_flow_control flow_ctrl;
+	const size_t len = sizeof(flow_ctrl);
 	int	rv;
 	unsigned long	flags;
 
 	spin_lock_irqsave(&cl->fc_spinlock, flags);
-	ishtp_hbm_hdr(ishtp_hdr, len);
-	ishtp_hbm_cl_hdr(cl, ISHTP_FLOW_CONTROL_CMD, data, len);
+
+	ishtp_hbm_hdr(&hdr, len);
+	ishtp_hbm_cl_hdr(cl, ISHTP_FLOW_CONTROL_CMD, &flow_ctrl, len);
 
 	/*
 	 * Sync possible race when RB recycle and packet receive paths
@@ -315,7 +292,7 @@ int ishtp_hbm_cl_flow_control_req(struct ishtp_device *dev,
 
 	cl->recv_msg_num_frags = 0;
 
-	rv = ishtp_write_message(dev, ishtp_hdr, data);
+	rv = ishtp_write_message(dev, &hdr, &flow_ctrl);
 	if (!rv) {
 		++cl->out_flow_ctrl_creds;
 		++cl->out_flow_ctrl_cnt;
@@ -345,14 +322,13 @@ int ishtp_hbm_cl_flow_control_req(struct ishtp_device *dev,
 int ishtp_hbm_cl_disconnect_req(struct ishtp_device *dev, struct ishtp_cl *cl)
 {
 	struct ishtp_msg_hdr hdr;
-	unsigned char data[128];
-	struct ishtp_msg_hdr *ishtp_hdr = &hdr;
-	const size_t len = sizeof(struct hbm_client_connect_request);
+	struct hbm_client_connect_request disconn_req;
+	const size_t len = sizeof(disconn_req);
 
-	ishtp_hbm_hdr(ishtp_hdr, len);
-	ishtp_hbm_cl_hdr(cl, CLIENT_DISCONNECT_REQ_CMD, data, len);
+	ishtp_hbm_hdr(&hdr, len);
+	ishtp_hbm_cl_hdr(cl, CLIENT_DISCONNECT_REQ_CMD, &disconn_req, len);
 
-	return ishtp_write_message(dev, ishtp_hdr, data);
+	return ishtp_write_message(dev, &hdr, &disconn_req);
 }
 
 /**
@@ -391,14 +367,13 @@ static void ishtp_hbm_cl_disconnect_res(struct ishtp_device *dev,
 int ishtp_hbm_cl_connect_req(struct ishtp_device *dev, struct ishtp_cl *cl)
 {
 	struct ishtp_msg_hdr hdr;
-	unsigned char data[128];
-	struct ishtp_msg_hdr *ishtp_hdr = &hdr;
-	const size_t len = sizeof(struct hbm_client_connect_request);
+	struct hbm_client_connect_request conn_req;
+	const size_t len = sizeof(conn_req);
 
-	ishtp_hbm_hdr(ishtp_hdr, len);
-	ishtp_hbm_cl_hdr(cl, CLIENT_CONNECT_REQ_CMD, data, len);
+	ishtp_hbm_hdr(&hdr, len);
+	ishtp_hbm_cl_hdr(cl, CLIENT_CONNECT_REQ_CMD, &conn_req, len);
 
-	return ishtp_write_message(dev, ishtp_hdr, data);
+	return ishtp_write_message(dev, &hdr, &conn_req);
 }
 
 /**