net: stmmac: set get_rx_header_len() as void for it didn't have any error code to return

We found the following warning when using W=1 to build kernel:

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:3634:6: warning: variable ‘ret’ set but not used [-Wunused-but-set-variable]
int ret, coe = priv->hw->rx_csum;

When digging stmmac_get_rx_header_len(), dwmac4_get_rx_header_len() and
dwxgmac2_get_rx_header_len() return 0 only, without any error code to
report. Therefore, it's better to define get_rx_header_len() as void.
Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac4_descs.c

@@ -494,10 +494,9 @@ static void dwmac4_set_vlan(struct dma_desc *p, u32 type)
 	p->des2 |= cpu_to_le32(type & TDES2_VLAN_TAG_MASK);
 }
 
-static int dwmac4_get_rx_header_len(struct dma_desc *p, unsigned int *len)
+static void dwmac4_get_rx_header_len(struct dma_desc *p, unsigned int *len)
 {
 	*len = le32_to_cpu(p->des2) & RDES2_HL;
-	return 0;
 }
 
 static void dwmac4_set_sec_addr(struct dma_desc *p, dma_addr_t addr)

drivers/net/ethernet/stmicro/stmmac/dwxgmac2_descs.c

@@ -286,11 +286,10 @@ static int dwxgmac2_get_rx_hash(struct dma_desc *p, u32 *hash,
 	return -EINVAL;
 }
 
-static int dwxgmac2_get_rx_header_len(struct dma_desc *p, unsigned int *len)
+static void dwxgmac2_get_rx_header_len(struct dma_desc *p, unsigned int *len)
 {
 	if (le32_to_cpu(p->des3) & XGMAC_RDES3_L34T)
 		*len = le32_to_cpu(p->des2) & XGMAC_RDES2_HL;
-	return 0;
 }
 
 static void dwxgmac2_set_sec_addr(struct dma_desc *p, dma_addr_t addr)

drivers/net/ethernet/stmicro/stmmac/hwif.h

@@ -90,7 +90,7 @@ struct stmmac_desc_ops {
 	/* RSS */
 	int (*get_rx_hash)(struct dma_desc *p, u32 *hash,
 			   enum pkt_hash_types *type);
-	int (*get_rx_header_len)(struct dma_desc *p, unsigned int *len);
+	void (*get_rx_header_len)(struct dma_desc *p, unsigned int *len);
 	void (*set_sec_addr)(struct dma_desc *p, dma_addr_t addr);
 	void (*set_sarc)(struct dma_desc *p, u32 sarc_type);
 	void (*set_vlan_tag)(struct dma_desc *p, u16 tag, u16 inner_tag,
@@ -150,7 +150,7 @@ struct stmmac_desc_ops {
 #define stmmac_get_rx_hash(__priv, __args...) \
 	stmmac_do_callback(__priv, desc, get_rx_hash, __args)
 #define stmmac_get_rx_header_len(__priv, __args...) \
-	stmmac_do_callback(__priv, desc, get_rx_header_len, __args)
+	stmmac_do_void_callback(__priv, desc, get_rx_header_len, __args)
 #define stmmac_set_desc_sec_addr(__priv, __args...) \
 	stmmac_do_void_callback(__priv, desc, set_sec_addr, __args)
 #define stmmac_set_desc_sarc(__priv, __args...) \

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -3630,15 +3630,15 @@ static unsigned int stmmac_rx_buf1_len(struct stmmac_priv *priv,
 				       struct dma_desc *p,
 				       int status, unsigned int len)
 {
-	int ret, coe = priv->hw->rx_csum;
 	unsigned int plen = 0, hlen = 0;
+	int coe = priv->hw->rx_csum;
 
 	/* Not first descriptor, buffer is always zero */
 	if (priv->sph && len)
 		return 0;
 
 	/* First descriptor, get split header length */
-	ret = stmmac_get_rx_header_len(priv, p, &hlen);
+	stmmac_get_rx_header_len(priv, p, &hlen);
 	if (priv->sph && hlen) {
 		priv->xstats.rx_split_hdr_pkt_n++;
 		return hlen;