Subject: Re: Qualcomm rmnet driver and qmi_wwan

From: Subash Abhinov Kasiviswanathan <[email-masked]>
Date: Sat, 09 Jun 2018 11:55:22 -0600

> thanks, I will test it on Monday.
> 
> Just a question for my knowledge: is the new sysfs attribute really
> needed? I mean, is there not any other way to understand from qmi_wwan
> without user intervention that there is the rmnet device attached?
> 
> Regards,
> Daniele
> 

Hi Daniele

You can check for the rx_handler attached to qmi_wwan dev and see if it
belongs to rmnet. You can use the attached patch for it but it think the
sysfs way might be a bit cleaner.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

From f7a2b90948da47ade1b345eddb37b721f5ab65f4 Mon Sep 17 00:00:00 2001
From: Subash Abhinov Kasiviswanathan <[email-masked]>
Date: Sat, 9 Jun 2018 11:14:22 -0600
Subject: [PATCH] net: qmi_wwan: Allow packets to pass through to rmnet

Pass through mode is to allow packets in MAP format to be passed
on to rmnet if the rmnet rx handler is attached to it.

Signed-off-by: Subash Abhinov Kasiviswanathan <[email-masked]>
---
 drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c |  4 +++-
 drivers/net/usb/qmi_wwan.c                         | 10 ++++++++++
 include/linux/if_rmnet.h                           | 20 ++++++++++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/if_rmnet.h

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
index 5f4e447..164a18f 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
@@ -17,6 +17,7 @@
 #include <linux/module.h>
 #include <linux/netlink.h>
 #include <linux/netdevice.h>
+#include <linux/if_rmnet.h>
 #include "rmnet_config.h"
 #include "rmnet_handlers.h"
 #include "rmnet_vnd.h"
@@ -48,10 +49,11 @@
 	[IFLA_RMNET_FLAGS]	= { .len = sizeof(struct ifla_rmnet_flags) },
 };
 
-static int rmnet_is_real_dev_registered(const struct net_device *real_dev)
+int rmnet_is_real_dev_registered(const struct net_device *real_dev)
 {
 	return rcu_access_pointer(real_dev->rx_handler) == rmnet_rx_handler;
 }
+EXPORT_SYMBOL(rmnet_is_real_dev_registered);
 
 /* Needs rtnl lock */
 static struct rmnet_port*
diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
index f52a9be..abdae63 100644
--- a/drivers/net/usb/qmi_wwan.c
+++ b/drivers/net/usb/qmi_wwan.c
@@ -22,6 +22,7 @@
 #include <linux/usb/cdc.h>
 #include <linux/usb/usbnet.h>
 #include <linux/usb/cdc-wdm.h>
+#include <linux/if_rmnet.h>
 
 /* This driver supports wwan (3G/LTE/?) devices using a vendor
  * specific management protocol called Qualcomm MSM Interface (QMI) -
@@ -354,6 +355,10 @@ static ssize_t add_mux_store(struct device *d,  struct device_attribute *attr, c
 	if (kstrtou8(buf, 0, &mux_id))
 		return -EINVAL;
 
+	/* rmnet is already attached here */
+	if (rmnet_is_real_dev_registered(to_net_dev(d)))
+		return -EINVAL;
+
 	/* mux_id [1 - 0x7f] range empirically found */
 	if (mux_id < 1 || mux_id > 0x7f)
 		return -EINVAL;
@@ -543,6 +548,11 @@ static int qmi_wwan_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 	if (skb->len < dev->net->hard_header_len)
 		return 0;
 
+	if (rawip && rmnet_is_real_dev_registered(skb->dev)) {
+		skb->protocol = htons(ETH_P_MAP);
+		return (netif_rx(skb) == NET_RX_SUCCESS);
+	}
+
 	if (info->flags & QMI_WWAN_FLAG_MUX)
 		return qmimux_rx_fixup(dev, skb);
 
diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h
new file mode 100644
index 0000000..7a7fb96
--- /dev/null
+++ b/include/linux/if_rmnet.h
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2018, The Linux Foundation. All rights reserved.
+ *
+ */
+#ifndef _LINUX_IF_RMNET_H_
+#define _LINUX_IF_RMNET_H_
+#include <linux/netdevice.h>
+
+#if defined(CONFIG_RMNET)
+extern int rmnet_is_real_dev_registered(const struct net_device *real_dev);
+#else
+static inline
+int rmnet_is_real_dev_registered(const struct net_device *real_dev)
+{
+	return 0;
+}
+#endif
+
+#endif /* !(_LINUX_IF_RMNET_H_) */
-- 
1.9.1