ath10k: wmi: Use struct_size() helper in ath10k_wmi_alloc_skb()

Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes. Also, remove unnecessary
variable _len_.

This code was detected with the help of Coccinelle and, audited and
fixed manually.
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200616225132.GA19873@embeddedor

drivers/net/wireless/ath/ath10k/wmi.c

@@ -6552,7 +6552,7 @@ static struct sk_buff *ath10k_wmi_op_gen_init(struct ath10k *ar)
 	struct wmi_init_cmd *cmd;
 	struct sk_buff *buf;
 	struct wmi_resource_config config = {};
-	u32 len, val;
+	u32 val;
 
 	config.num_vdevs = __cpu_to_le32(TARGET_NUM_VDEVS);
 	config.num_peers = __cpu_to_le32(TARGET_NUM_PEERS);
@@ -6604,10 +6604,8 @@ static struct sk_buff *ath10k_wmi_op_gen_init(struct ath10k *ar)
 	config.num_msdu_desc = __cpu_to_le32(TARGET_NUM_MSDU_DESC);
 	config.max_frag_entries = __cpu_to_le32(TARGET_MAX_FRAG_ENTRIES);
 
-	len = sizeof(*cmd) +
-	      (sizeof(struct host_memory_chunk) * ar->wmi.num_mem_chunks);
-
-	buf = ath10k_wmi_alloc_skb(ar, len);
+	buf = ath10k_wmi_alloc_skb(ar, struct_size(cmd, mem_chunks.items,
+						   ar->wmi.num_mem_chunks));
 	if (!buf)
 		return ERR_PTR(-ENOMEM);
 
@@ -6625,7 +6623,7 @@ static struct sk_buff *ath10k_wmi_10_1_op_gen_init(struct ath10k *ar)
 	struct wmi_init_cmd_10x *cmd;
 	struct sk_buff *buf;
 	struct wmi_resource_config_10x config = {};
-	u32 len, val;
+	u32 val;
 
 	config.num_vdevs = __cpu_to_le32(TARGET_10X_NUM_VDEVS);
 	config.num_peers = __cpu_to_le32(TARGET_10X_NUM_PEERS);
@@ -6669,10 +6667,8 @@ static struct sk_buff *ath10k_wmi_10_1_op_gen_init(struct ath10k *ar)
 	config.num_msdu_desc = __cpu_to_le32(TARGET_10X_NUM_MSDU_DESC);
 	config.max_frag_entries = __cpu_to_le32(TARGET_10X_MAX_FRAG_ENTRIES);
 
-	len = sizeof(*cmd) +
-	      (sizeof(struct host_memory_chunk) * ar->wmi.num_mem_chunks);
-
-	buf = ath10k_wmi_alloc_skb(ar, len);
+	buf = ath10k_wmi_alloc_skb(ar, struct_size(cmd, mem_chunks.items,
+						   ar->wmi.num_mem_chunks));
 	if (!buf)
 		return ERR_PTR(-ENOMEM);
 
@@ -6690,7 +6686,7 @@ static struct sk_buff *ath10k_wmi_10_2_op_gen_init(struct ath10k *ar)
 	struct wmi_init_cmd_10_2 *cmd;
 	struct sk_buff *buf;
 	struct wmi_resource_config_10x config = {};
-	u32 len, val, features;
+	u32 val, features;
 
 	config.num_vdevs = __cpu_to_le32(TARGET_10X_NUM_VDEVS);
 	config.num_peer_keys = __cpu_to_le32(TARGET_10X_NUM_PEER_KEYS);
@@ -6742,10 +6738,8 @@ static struct sk_buff *ath10k_wmi_10_2_op_gen_init(struct ath10k *ar)
 	config.num_msdu_desc = __cpu_to_le32(TARGET_10X_NUM_MSDU_DESC);
 	config.max_frag_entries = __cpu_to_le32(TARGET_10X_MAX_FRAG_ENTRIES);
 
-	len = sizeof(*cmd) +
-	      (sizeof(struct host_memory_chunk) * ar->wmi.num_mem_chunks);
-
-	buf = ath10k_wmi_alloc_skb(ar, len);
+	buf = ath10k_wmi_alloc_skb(ar, struct_size(cmd, mem_chunks.items,
+						   ar->wmi.num_mem_chunks));
 	if (!buf)
 		return ERR_PTR(-ENOMEM);
 
@@ -6777,7 +6771,6 @@ static struct sk_buff *ath10k_wmi_10_4_op_gen_init(struct ath10k *ar)
 	struct wmi_init_cmd_10_4 *cmd;
 	struct sk_buff *buf;
 	struct wmi_resource_config_10_4 config = {};
-	u32 len;
 
 	config.num_vdevs = __cpu_to_le32(ar->max_num_vdevs);
 	config.num_peers = __cpu_to_le32(ar->max_num_peers);
@@ -6839,10 +6832,8 @@ static struct sk_buff *ath10k_wmi_10_4_op_gen_init(struct ath10k *ar)
 	config.iphdr_pad_config = __cpu_to_le32(TARGET_10_4_IPHDR_PAD_CONFIG);
 	config.qwrap_config = __cpu_to_le32(TARGET_10_4_QWRAP_CONFIG);
 
-	len = sizeof(*cmd) +
-	      (sizeof(struct host_memory_chunk) * ar->wmi.num_mem_chunks);
-
-	buf = ath10k_wmi_alloc_skb(ar, len);
+	buf = ath10k_wmi_alloc_skb(ar, struct_size(cmd, mem_chunks.items,
+						   ar->wmi.num_mem_chunks));
 	if (!buf)
 		return ERR_PTR(-ENOMEM);
 
@@ -7550,12 +7541,9 @@ ath10k_wmi_op_gen_scan_chan_list(struct ath10k *ar,
 	struct sk_buff *skb;
 	struct wmi_channel_arg *ch;
 	struct wmi_channel *ci;
-	int len;
 	int i;
 
-	len = sizeof(*cmd) + arg->n_channels * sizeof(struct wmi_channel);
-
-	skb = ath10k_wmi_alloc_skb(ar, len);
+	skb = ath10k_wmi_alloc_skb(ar, struct_size(cmd, chan_info, arg->n_channels));
 	if (!skb)
 		return ERR_PTR(-EINVAL);