netdev - Re: [PATCH net-next v4] net/ncsi: Add NCSI Broadcom OEM command

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Date:   Mon, 15 Oct 2018 17:27:19 +0000
From:   Vijay Khemka <vijaykhemka@...com>
To:     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>
CC:     "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>
Subject: Re: [PATCH net-next v4] net/ncsi: Add NCSI Broadcom OEM command



On 10/14/18, 8:51 PM, "Samuel Mendoza-Jonas" <sam@...dozajonas.com> wrote:

    On Mon, 2018-10-15 at 13:08 +1100, Samuel Mendoza-Jonas wrote:
    > On Fri, 2018-10-12 at 11:20 -0700, Vijay Khemka wrote:
    > > This patch adds OEM Broadcom commands and response handling. It also
    > > defines OEM Get MAC Address handler to get and configure the device.
    > > 
    > > ncsi_oem_gma_handler_bcm: This handler send NCSI broadcom command for
    > > getting mac address.
    > > ncsi_rsp_handler_oem_bcm: This handles response received for all
    > > broadcom OEM commands.
    > > ncsi_rsp_handler_oem_bcm_gma: This handles get mac address response and
    > > set it to device.
    > > 
    > > Signed-off-by: Vijay Khemka <vijaykhemka@...com>
    > > ---
    > >  v4: updated as per comment from Sam, I was just wondering if I can remove
    > >  NCSI_OEM_CMD_GET_MAC config option and let this code be valid always and
    > >  it will configure mac address if there is get mac address handler for given 
    > >  manufacture id.
    > 
    > Hi Vijay,
    > 
    > We can look at handling this a different way, but I don't think we want
    > to unconditionally set the system's MAC address based on the OEM GMA
    > command. If the user wants to set a custom MAC address, or in the case of
    > OpenBMC for example who have their MAC address saved in flash, this will
    > override that value with whatever the Network Controller has saved. In
    > particular as it is set up it will override any MAC address every time a
    > channel is configured, such as during a failover event.
    > 
    > We *could* always send the GMA command if it is available and move the
    > decision whether to use the resulting address or not into the response
    > handler. That would simplify the ncsi_configure_channel() logic a bit.
    > Another idea may be to have a Netlink command to tell NCSI to ignore the
    > GMA result; then we could drop the config option and the system can
    > safely change the address if desired.
    > 
    > Any thoughts? I'll also ping some of the OpenBMC people and see what
    > their expectations are.
    
    After a bit of a think and an ask around, to quote a colleague:
    > I think we'd want it handled (overall) like any other net device; the MAC
    > address in the device's ROM provides a default, and is overridden by anything
    > specified by userspace 
    
    Which describes what I was thinking pretty well.
    So if we can have it such that the NCSI driver only sets the MAC address
    _once_, and then after then does not update it again, we should be able to call
    the OEM GMA command without hiding it behind a config option. So the first time
    a channel was configured we store and set the MAC address given, but then on
    later configure events we don't continue to update it. What do you think?
    
    Cheers,
    Sam

  I agree with you setting it only once. I gave a thought about config option and realize that 
  we should allow user to configure it. If user wants to set mac address through device tree 
  and not through ROM then we must not override mac set by device tree. So my proposal is 
  setting of mac address in response should be hidden under config option. Getting mac address 
  can still go without config option. Your thought?
    
    > 
    > > +#if IS_ENABLED(CONFIG_NCSI_OEM_CMD_GET_MAC)
    > > +
    > > +/* NCSI OEM Command APIs */
    > > +static void ncsi_oem_gma_handler_bcm(struct ncsi_cmd_arg *nca)
    > > +{
    > > +	unsigned char data[NCSI_OEM_BCM_CMD_GMA_LEN];
    > > +	int ret = 0;
    > > +
    > > +	nca->payload = NCSI_OEM_BCM_CMD_GMA_LEN;
    > > +
    > > +	memset(data, 0, NCSI_OEM_BCM_CMD_GMA_LEN);
    > > +	*(unsigned int *)data = ntohl(NCSI_OEM_MFR_BCM_ID);
    > > +	data[5] = NCSI_OEM_BCM_CMD_GMA;
    > > +
    > > +	nca->data = data;
    > > +
    > > +	ret = ncsi_xmit_cmd(nca);
    > > +	if (ret)
    > > +		netdev_err(nca->ndp->ndev.dev,
    > > +			   "NCSI: Failed to transmit cmd 0x%x during configure\n",
    > > +			   nca->type);
    > > +}
    > 
    > As a side note while unlikely we probably want to propagate the return
    > value of ncsi_xmit_cmd() from here; otherwise we'll miss a failure and
    > the configure process will stall.
    > 
    > Regards,
    > Sam
    > 
  I will take care of this.