Subject: Re: [PATCH net-next 3/6] net: qualcomm: rmnet: kill RMNET_MAP_GET_*() accessor macros

From: Bjorn Andersson <[email-masked]>
Date: Thu, 4 Mar 2021 22:16:55 -0600

On Thu 04 Mar 16:34 CST 2021, 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.
> 
> In "rmnet_map_data.c", use sizeof(object) rather than sizeof(type)
> in one spot.  Also,there's no need to byte swap 0; it's all zeros
> irrespective of endianness.
> 

Reviewed-by: Bjorn Andersson <[email-masked]>

Regards,
Bjorn

> Signed-off-by: Alex Elder <[email-masked]>
> ---
>  drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c | 10 ++++++----
>  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, 16 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c
> index 3d00b32323084..2a6b2a609884c 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c
> @@ -56,20 +56,22 @@ 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) {
> +		/* Packet contains a MAP command (not data) */
>  		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 576501db2a0bc..2aea153f42473 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
> @@ -32,18 +32,6 @@ enum rmnet_map_commands {
>  	RMNET_MAP_COMMAND_ENUM_LENGTH
>  };
>  
> -#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 beaee49621287..add0f5ade2e61 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_command.c
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_command.c
> @@ -12,12 +12,13 @@ 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);
> @@ -49,6 +50,7 @@ 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;
>  
> @@ -58,7 +60,8 @@ 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 MAP header */
> +	cmd = (struct rmnet_map_control_command *)(map_header + 1);
>  	cmd->cmd_type = type & 0x03;
>  
>  	netif_tx_lock(dev);
> @@ -71,11 +74,13 @@ 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 MAP 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 bd1aa11c9ce59..fd55269c2ce3c 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
> @@ -321,7 +321,7 @@ 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);
> @@ -330,7 +330,7 @@ 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
>