Commit 16653c16 authored by Alex Elder's avatar Alex Elder Committed by David S. Miller
Browse files

net: qualcomm: rmnet: use masks instead of C bit-fields 



The actual layout of bits defined in C bit-fields (e.g. int foo : 3)
is implementation-defined.  Structures defined in <linux/if_rmnet.h>
address this by specifying all bit-fields twice, to cover two
possible layouts.

I think this pattern is repetitive and noisy, and I find the whole
notion of compiler "bitfield endianness" to be non-intuitive.

Stop using C bit-fields for the command/data flag and the pad length
fields in the rmnet_map structure, and define a single-byte flags
field instead.  Define a mask for the single-bit "command" flag,
and another mask for the encoded pad length.  The content of both
fields can be accessed using a simple bitwise AND operation.

Signed-off-by: default avatarAlex Elder <elder@linaro.org>
Reviewed-by: default avatarBjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: default avatarAlexander Duyck <alexanderduyck@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9d131d04

drivers/net/ethernet/qualcomm/rmnet/rmnet_handlers.c

+2 −2
Original line number Diff line number Diff line
@@ -61,7 +61,7 @@ __rmnet_map_ingress_handler(struct sk_buff *skb, 
	u16 len, pad;

	u8 mux_id;



	if (map_header->cd_bit) {

	if (map_header->flags & MAP_CMD_FLAG) {

		/* Packet contains a MAP command (not data) */

		if (port->data_format & RMNET_FLAGS_INGRESS_MAP_COMMANDS)

			return rmnet_map_command(skb, port);
@@ -70,7 +70,7 @@ __rmnet_map_ingress_handler(struct sk_buff *skb, 
	}



	mux_id = map_header->mux_id;

	pad = map_header->pad_len;

	pad = map_header->flags & MAP_PAD_LEN_MASK;

	len = ntohs(map_header->pkt_len) - pad;



	if (mux_id >= RMNET_MAX_LOGICAL_EP)

drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c

+3 −1
Original line number Diff line number Diff line
@@ -280,6 +280,7 @@ struct rmnet_map_header *rmnet_map_add_map_header(struct sk_buff *skb, 
		return map_header;

	}



	BUILD_BUG_ON(MAP_PAD_LEN_MASK < 3);

	padding = ALIGN(map_datalen, 4) - map_datalen;



	if (padding == 0)
@@ -293,7 +294,8 @@ struct rmnet_map_header *rmnet_map_add_map_header(struct sk_buff *skb, 


done:

	map_header->pkt_len = htons(map_datalen + padding);

	map_header->pad_len = padding & 0x3F;

	/* This is a data packet, so the CMD bit is 0 */

	map_header->flags = padding & MAP_PAD_LEN_MASK;



	return map_header;

}

include/linux/if_rmnet.h

+10 −13
Original line number Diff line number Diff line
@@ -6,21 +6,18 @@ 
#define _LINUX_IF_RMNET_H_



struct rmnet_map_header {

#if defined(__LITTLE_ENDIAN_BITFIELD)

	u8  pad_len:6;

	u8  reserved_bit:1;

	u8  cd_bit:1;

#elif defined (__BIG_ENDIAN_BITFIELD)

	u8  cd_bit:1;

	u8  reserved_bit:1;

	u8  pad_len:6;

#else

#error	"Please fix <asm/byteorder.h>"

#endif

	u8 flags;			/* MAP_CMD_FLAG, MAP_PAD_LEN_MASK */

	u8 mux_id;

	__be16 pkt_len;

	__be16 pkt_len;			/* Length of packet, including pad */

}  __aligned(1);



/* rmnet_map_header flags field:

 *  PAD_LEN:	number of pad bytes following packet data

 *  CMD:	1 = packet contains a MAP command; 0 = packet contains data

 */

#define MAP_PAD_LEN_MASK		GENMASK(5, 0)

#define MAP_CMD_FLAG			BIT(7)



struct rmnet_map_dl_csum_trailer {

	u8  reserved1;

#if defined(__LITTLE_ENDIAN_BITFIELD)