net/ncsi: Add NCSI OEM command support

This patch adds OEM commands and response handling. It also defines OEM
command and response structure as per NCSI specification along with its
handlers.

ncsi_cmd_handler_oem: This is a generic command request handler for OEM
commands
ncsi_rsp_handler_oem: This is a generic response handler for OEM commands

Signed-off-by: Vijay Khemka <vijaykhemka@fb.com>
Reviewed-by: Justin Lee <justin.lee1@dell.com>
Reviewed-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ncsi/ncsi-cmd.c

@@ -211,6 +211,25 @@ static int ncsi_cmd_handler_snfc(struct sk_buff *skb,
 	return 0;
 }
 
+static int ncsi_cmd_handler_oem(struct sk_buff *skb,
+				struct ncsi_cmd_arg *nca)
+{
+	struct ncsi_cmd_oem_pkt *cmd;
+	unsigned int len;
+
+	len = sizeof(struct ncsi_cmd_pkt_hdr) + 4;
+	if (nca->payload < 26)
+		len += 26;
+	else
+		len += nca->payload;
+
+	cmd = skb_put_zero(skb, len);
+	memcpy(&cmd->mfr_id, nca->data, nca->payload);
+	ncsi_cmd_build_header(&cmd->cmd.common, nca);
+
+	return 0;
+}
+
 static struct ncsi_cmd_handler {
 	unsigned char type;
 	int           payload;
@@ -244,7 +263,7 @@ static struct ncsi_cmd_handler {
 	{ NCSI_PKT_CMD_GNS,    0, ncsi_cmd_handler_default },
 	{ NCSI_PKT_CMD_GNPTS,  0, ncsi_cmd_handler_default },
 	{ NCSI_PKT_CMD_GPS,    0, ncsi_cmd_handler_default },
-	{ NCSI_PKT_CMD_OEM,    0, NULL                     },
+	{ NCSI_PKT_CMD_OEM,   -1, ncsi_cmd_handler_oem     },
 	{ NCSI_PKT_CMD_PLDM,   0, NULL                     },
 	{ NCSI_PKT_CMD_GPUUID, 0, ncsi_cmd_handler_default }
 };
@@ -316,8 +335,13 @@ int ncsi_xmit_cmd(struct ncsi_cmd_arg *nca)
 		return -ENOENT;
 	}
 
-	/* Get packet payload length and allocate the request */
-	nca->payload = nch->payload;
+	/* Get packet payload length and allocate the request
+	 * It is expected that if length set as negative in
+	 * handler structure means caller is initializing it
+	 * and setting length in nca before calling xmit function
+	 */
+	if (nch->payload >= 0)
+		nca->payload = nch->payload;
 	nr = ncsi_alloc_command(nca);
 	if (!nr)
 		return -ENOMEM;