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Date:   Mon, 20 May 2019 08:41:08 -0700
From:   Bjorn Andersson <bjorn.andersson@linaro.org>
To:     Alex Elder <elder@linaro.org>
Cc:     arnd@arndb.de, subashab@codeaurora.org, david.brown@linaro.org,
        agross@kernel.org, davem@davemloft.net,
        ilias.apalodimas@linaro.org, cpratapa@codeaurora.org,
        syadagir@codeaurora.org, evgreen@chromium.org, benchan@google.com,
        ejcaruso@google.com, netdev@vger.kernel.org,
        linux-arm-msm@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/8] net: qualcomm: rmnet: kill RMNET_MAP_GET_*()
 accessor macros
Message-ID: <20190520154108.GQ2085@tuxbook-pro>
References: <20190520135354.18628-1-elder@linaro.org>
 <20190520135354.18628-3-elder@linaro.org>
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On Mon 20 May 06:53 PDT 2019, Alex Elder wrote:

> The following macros, defined in "rmnet_map.h", assume a socket
> buffer is provided as an argument without any real indication this
> is the case.
>     RMNET_MAP_GET_MUX_ID()
>     RMNET_MAP_GET_CD_BIT()
>     RMNET_MAP_GET_PAD()
>     RMNET_MAP_GET_CMD_START()
>     RMNET_MAP_GET_LENGTH()
> What they hide is pretty trivial accessing of fields in a structure,
> and it's much clearer to see this if we do these accesses directly.
> 
> So rather than using these accessor macros, assign a local
> variable of the map header pointer type to the socket buffer data
> pointer, and derereference that pointer variable.
> 
> Use the network byte order macros (e.g., ntohs()), not the Linux
> byte order functions (e.g. be_to_cpu16()) to convert the big-endian
> packet length field, to match the convention used elswhere in the
> driver.
> 
> There's no need to byte swap 0; it's all zeros irrespective of
> endianness.
> 

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

> Signed-off-by: Alex Elder <elder@linaro.org>
> ---
>  drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c |  9 +++++----
>  drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h      | 12 ------------
>  .../net/ethernet/qualcomm/rmnet/rmnet_map_command.c  | 11 ++++++++---
>  drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c |  4 ++--
>  4 files changed, 15 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c
> index 11167abe5934..4c1b62b72504 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c
> @@ -65,20 +65,21 @@ static void
>  __rmnet_map_ingress_handler(struct sk_buff *skb,
>  			    struct rmnet_port *port)
>  {
> +	struct rmnet_map_header *map_header = (void *)skb->data;
>  	struct rmnet_endpoint *ep;
>  	u16 len, pad;
>  	u8 mux_id;
>  
> -	if (RMNET_MAP_GET_CD_BIT(skb)) {
> +	if (map_header->cd_bit) {
>  		if (port->data_format & RMNET_FLAGS_INGRESS_MAP_COMMANDS)
>  			return rmnet_map_command(skb, port);
>  
>  		goto free_skb;
>  	}
>  
> -	mux_id = RMNET_MAP_GET_MUX_ID(skb);
> -	pad = RMNET_MAP_GET_PAD(skb);
> -	len = RMNET_MAP_GET_LENGTH(skb) - pad;
> +	mux_id = map_header->mux_id;
> +	pad = map_header->pad_len;
> +	len = ntohs(map_header->pkt_len) - pad;
>  
>  	if (mux_id >= RMNET_MAX_LOGICAL_EP)
>  		goto free_skb;
> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
> index b1ae9499c0b2..a30a7b405a11 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
> @@ -63,18 +63,6 @@ struct rmnet_map_ul_csum_header {
>  	u16 csum_enabled:1;
>  } __aligned(1);
>  
> -#define RMNET_MAP_GET_MUX_ID(Y) (((struct rmnet_map_header *) \
> -				 (Y)->data)->mux_id)
> -#define RMNET_MAP_GET_CD_BIT(Y) (((struct rmnet_map_header *) \
> -				(Y)->data)->cd_bit)
> -#define RMNET_MAP_GET_PAD(Y) (((struct rmnet_map_header *) \
> -				(Y)->data)->pad_len)
> -#define RMNET_MAP_GET_CMD_START(Y) ((struct rmnet_map_control_command *) \
> -				    ((Y)->data + \
> -				      sizeof(struct rmnet_map_header)))
> -#define RMNET_MAP_GET_LENGTH(Y) (ntohs(((struct rmnet_map_header *) \
> -					(Y)->data)->pkt_len))
> -
>  #define RMNET_MAP_COMMAND_REQUEST     0
>  #define RMNET_MAP_COMMAND_ACK         1
>  #define RMNET_MAP_COMMAND_UNSUPPORTED 2
> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_command.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_command.c
> index f6cf59aee212..f675f47c3495 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_command.c
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_command.c
> @@ -20,12 +20,13 @@ static u8 rmnet_map_do_flow_control(struct sk_buff *skb,
>  				    struct rmnet_port *port,
>  				    int enable)
>  {
> +	struct rmnet_map_header *map_header = (void *)skb->data;
>  	struct rmnet_endpoint *ep;
>  	struct net_device *vnd;
>  	u8 mux_id;
>  	int r;
>  
> -	mux_id = RMNET_MAP_GET_MUX_ID(skb);
> +	mux_id = map_header->mux_id;
>  
>  	if (mux_id >= RMNET_MAX_LOGICAL_EP) {
>  		kfree_skb(skb);
> @@ -57,6 +58,7 @@ static void rmnet_map_send_ack(struct sk_buff *skb,
>  			       unsigned char type,
>  			       struct rmnet_port *port)
>  {
> +	struct rmnet_map_header *map_header = (void *)skb->data;
>  	struct rmnet_map_control_command *cmd;
>  	struct net_device *dev = skb->dev;
>  
> @@ -66,7 +68,8 @@ static void rmnet_map_send_ack(struct sk_buff *skb,
>  
>  	skb->protocol = htons(ETH_P_MAP);
>  
> -	cmd = RMNET_MAP_GET_CMD_START(skb);
> +	/* Command data immediately follows the header */
> +	cmd = (struct rmnet_map_control_command *)(map_header + 1);
>  	cmd->cmd_type = type & 0x03;
>  
>  	netif_tx_lock(dev);
> @@ -79,11 +82,13 @@ static void rmnet_map_send_ack(struct sk_buff *skb,
>   */
>  void rmnet_map_command(struct sk_buff *skb, struct rmnet_port *port)
>  {
> +	struct rmnet_map_header *map_header = (void *)skb->data;
>  	struct rmnet_map_control_command *cmd;
>  	unsigned char command_name;
>  	unsigned char rc = 0;
>  
> -	cmd = RMNET_MAP_GET_CMD_START(skb);
> +	/* Command data immediately follows the header */
> +	cmd = (struct rmnet_map_control_command *)(map_header + 1);
>  	command_name = cmd->command_name;
>  
>  	switch (command_name) {
> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
> index 57a9c314a665..498f20ba1826 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
> @@ -323,7 +323,7 @@ struct sk_buff *rmnet_map_deaggregate(struct sk_buff *skb,
>  		return NULL;
>  
>  	maph = (struct rmnet_map_header *)skb->data;
> -	packet_len = ntohs(maph->pkt_len) + sizeof(struct rmnet_map_header);
> +	packet_len = ntohs(maph->pkt_len) + sizeof(*maph);
>  
>  	if (port->data_format & RMNET_FLAGS_INGRESS_MAP_CKSUMV4)
>  		packet_len += sizeof(struct rmnet_map_dl_csum_trailer);
> @@ -332,7 +332,7 @@ struct sk_buff *rmnet_map_deaggregate(struct sk_buff *skb,
>  		return NULL;
>  
>  	/* Some hardware can send us empty frames. Catch them */
> -	if (ntohs(maph->pkt_len) == 0)
> +	if (!maph->pkt_len)
>  		return NULL;
>  
>  	skbn = alloc_skb(packet_len + RMNET_MAP_DEAGGR_SPACING, GFP_ATOMIC);
> -- 
> 2.20.1
>