Re: [net-next PATCH RFC v6 08/16] net: dsa: tag_qca: add define for handling mdio Ethernet packet

[Vladimir Oltean <olteanv@gmail.com>]

On Tue, Dec 14, 2021 at 11:44:01PM +0100, Ansuel Smith wrote:
> Add all the required define to prepare support for mdio read/write in
> Ethernet packet. Any packet of this type has to be dropped as the only
> use of these special packet is receive ack for an mdio write request or
> receive data for an mdio read request.
> A struct is used that emulates the Ethernet header but is used for a
> different purpose.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
> ---
>  include/linux/dsa/tag_qca.h | 41 +++++++++++++++++++++++++++++++++++++
>  net/dsa/tag_qca.c           | 13 +++++++++---
>  2 files changed, 51 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/dsa/tag_qca.h b/include/linux/dsa/tag_qca.h
> index c02d2d39ff4a..21cd0db5acc2 100644
> --- a/include/linux/dsa/tag_qca.h
> +++ b/include/linux/dsa/tag_qca.h
> @@ -12,10 +12,51 @@
>  #define QCA_HDR_RECV_FRAME_IS_TAGGED	BIT(3)
>  #define QCA_HDR_RECV_SOURCE_PORT	GENMASK(2, 0)
>  
> +/* Packet type for recv */
> +#define QCA_HDR_RECV_TYPE_NORMAL	0x0
> +#define QCA_HDR_RECV_TYPE_MIB		0x1
> +#define QCA_HDR_RECV_TYPE_RW_REG_ACK	0x2
> +
>  #define QCA_HDR_XMIT_VERSION		GENMASK(15, 14)
>  #define QCA_HDR_XMIT_PRIORITY		GENMASK(13, 11)
>  #define QCA_HDR_XMIT_CONTROL		GENMASK(10, 8)
>  #define QCA_HDR_XMIT_FROM_CPU		BIT(7)
>  #define QCA_HDR_XMIT_DP_BIT		GENMASK(6, 0)
>  
> +/* Packet type for xmit */
> +#define QCA_HDR_XMIT_TYPE_NORMAL	0x0
> +#define QCA_HDR_XMIT_TYPE_RW_REG	0x1
> +
> +#define MDIO_CHECK_CODE_VAL		0x5
> +
> +/* Specific define for in-band MDIO read/write with Ethernet packet */
> +#define QCA_HDR_MDIO_SEQ_LEN		4 /* 4 byte for the seq */
> +#define QCA_HDR_MDIO_COMMAND_LEN	4 /* 4 byte for the command */
> +#define QCA_HDR_MDIO_DATA1_LEN		4 /* First 4 byte for the mdio data */
> +#define QCA_HDR_MDIO_HEADER_LEN		(QCA_HDR_MDIO_SEQ_LEN + \
> +					QCA_HDR_MDIO_COMMAND_LEN + \
> +					QCA_HDR_MDIO_DATA1_LEN)
> +
> +#define QCA_HDR_MDIO_DATA2_LEN		12 /* Other 12 byte for the mdio data */
> +#define QCA_HDR_MDIO_PADDING_LEN	34 /* Padding to reach the min Ethernet packet */
> +
> +#define QCA_HDR_MDIO_PKG_LEN		(QCA_HDR_MDIO_HEADER_LEN + \
> +					QCA_HDR_LEN + \
> +					QCA_HDR_MDIO_DATA2_LEN + \
> +					QCA_HDR_MDIO_PADDING_LEN)
> +
> +#define QCA_HDR_MDIO_SEQ_NUM		GENMASK(31, 0)  /* 63, 32 */
> +#define QCA_HDR_MDIO_CHECK_CODE		GENMASK(31, 29) /* 31, 29 */
> +#define QCA_HDR_MDIO_CMD		BIT(28)		/* 28 */
> +#define QCA_HDR_MDIO_LENGTH		GENMASK(23, 20) /* 23, 20 */
> +#define QCA_HDR_MDIO_ADDR		GENMASK(18, 0)  /* 18, 0 */
> +
> +/* Special struct emulating a Ethernet header */
> +struct mdio_ethhdr {
> +	u32 command;		/* command bit 31:0 */
> +	u32 seq;		/* seq 63:32 */
> +	u32 mdio_data;		/* first 4byte mdio */
> +	__be16 hdr;		/* qca hdr */
> +} __packed;
> +
>  #endif /* __TAG_QCA_H */
> diff --git a/net/dsa/tag_qca.c b/net/dsa/tag_qca.c
> index f8df49d5956f..d30249b5205d 100644
> --- a/net/dsa/tag_qca.c
> +++ b/net/dsa/tag_qca.c
> @@ -32,10 +32,10 @@ static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev)
>  
>  static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev)
>  {
> -	u8 ver;
> -	u16  hdr;
> -	int port;
> +	u16  hdr, pk_type;

Why the two spaces between "u16" and "hdr"?

>  	__be16 *phdr;
> +	int port;
> +	u8 ver;
>  
>  	if (unlikely(!pskb_may_pull(skb, QCA_HDR_LEN)))
>  		return NULL;
> @@ -48,6 +48,13 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev)
>  	if (unlikely(ver != QCA_HDR_VERSION))
>  		return NULL;
>  
> +	/* Get pk type */
> +	pk_type = FIELD_GET(QCA_HDR_RECV_TYPE, hdr);
> +
> +	/* Ethernet MDIO read/write packet */
> +	if (pk_type == QCA_HDR_RECV_TYPE_RW_REG_ACK)
> +		return NULL;
> +
>  	/* Remove QCA tag and recalculate checksum */
>  	skb_pull_rcsum(skb, QCA_HDR_LEN);
>  	dsa_strip_etype_header(skb, QCA_HDR_LEN);
> -- 
> 2.33.1
>