linux-kernel - Re:[PATCH net-next] net/ncsi: allow to customize BMC MAC Address offset

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Message-ID: <75DDAF9A-DABC-4670-BEC0-320185017642@fb.com>
Date:   Wed, 7 Aug 2019 17:36:47 +0000
From:   Vijay Khemka <vijaykhemka@...com>
To:     Tao Ren <taoren@...com>,
        Samuel Mendoza-Jonas <sam@...dozajonas.com>,
        "David S . Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        William Kennington <wak@...gle.com>,
        Joel Stanley <joel@....id.au>
Subject: Re:[PATCH net-next] net/ncsi: allow to customize BMC MAC Address
 offset

Lgtm except one small comment below.

On 8/6/19, 5:22 PM, "openbmc on behalf of Tao Ren" <openbmc-bounces+vijaykhemka=fb.com@...ts.ozlabs.org on behalf of taoren@...com> wrote:

    Currently BMC's MAC address is calculated by adding 1 to NCSI NIC's base
    MAC address when CONFIG_NCSI_OEM_CMD_GET_MAC option is enabled. The logic
    doesn't work for platforms with different BMC MAC offset: for example,
    Facebook Yamp BMC's MAC address is calculated by adding 2 to NIC's base
    MAC address ("BaseMAC + 1" is reserved for Host use).
    
    This patch adds NET_NCSI_MC_MAC_OFFSET config option to customize offset
    between NIC's Base MAC address and BMC's MAC address. Its default value is
    set to 1 to avoid breaking existing users.
    
    Signed-off-by: Tao Ren <taoren@...com>
    ---
     net/ncsi/Kconfig    |  8 ++++++++
     net/ncsi/ncsi-rsp.c | 15 +++++++++++++--
     2 files changed, 21 insertions(+), 2 deletions(-)
    
    diff --git a/net/ncsi/Kconfig b/net/ncsi/Kconfig
    index 2f1e5756c03a..be8efe1ed99e 100644
    --- a/net/ncsi/Kconfig
    +++ b/net/ncsi/Kconfig
    @@ -17,3 +17,11 @@ config NCSI_OEM_CMD_GET_MAC
     	---help---
     	  This allows to get MAC address from NCSI firmware and set them back to
     		controller.
    +config NET_NCSI_MC_MAC_OFFSET
    +	int
    +	prompt "Offset of Management Controller's MAC Address"
    +	depends on NCSI_OEM_CMD_GET_MAC
    +	default 1
    +	help
    +	  This defines the offset between Network Controller's (base) MAC
    +	  address and Management Controller's MAC address.
    diff --git a/net/ncsi/ncsi-rsp.c b/net/ncsi/ncsi-rsp.c
    index 7581bf919885..24a791f9ebf5 100644
    --- a/net/ncsi/ncsi-rsp.c
    +++ b/net/ncsi/ncsi-rsp.c
    @@ -656,6 +656,11 @@ static int ncsi_rsp_handler_oem_bcm_gma(struct ncsi_request *nr)
     	struct ncsi_rsp_oem_pkt *rsp;
     	struct sockaddr saddr;
     	int ret = 0;
    +#ifdef CONFIG_NET_NCSI_MC_MAC_OFFSET
    +	int mac_offset = CONFIG_NET_NCSI_MC_MAC_OFFSET;
    +#else
    +	int mac_offset = 1;
    +#endif
     
     	/* Get the response header */
     	rsp = (struct ncsi_rsp_oem_pkt *)skb_network_header(nr->rsp);
    @@ -663,8 +668,14 @@ static int ncsi_rsp_handler_oem_bcm_gma(struct ncsi_request *nr)
     	saddr.sa_family = ndev->type;
     	ndev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
     	memcpy(saddr.sa_data, &rsp->data[BCM_MAC_ADDR_OFFSET], ETH_ALEN);
    -	/* Increase mac address by 1 for BMC's address */
    -	eth_addr_inc((u8 *)saddr.sa_data);
    +
    +	/* Management Controller's MAC address is calculated by adding
    +	 * the offset to Network Controller's (base) MAC address.
    +	 * Note: negative offset is "ignored", and BMC will use the Base
Just mention negative and zero offset is ignored. As you are ignoring 0 as well.

    +	 * MAC address in this case.
    +	 */
    +	while (mac_offset-- > 0)
    +		eth_addr_inc((u8 *)saddr.sa_data);
     	if (!is_valid_ether_addr((const u8 *)saddr.sa_data))
     		return -ENXIO;
     
    -- 
    2.17.1