Date:	Tue, 2 Jul 2013 22:15:49 +0200 (CEST)
From:	Enrico Mioso <mrkiko.rs@...il.com>
To:	Enrico Mioso <mrkiko.rs@...il.com>
cc:	netdev@...r.kernel.org,
	Bjørn Mork <bjorn@...k.no>
Subject: Re: [PATCH RFC 3/3] huawei_cdc_ncm base skeleton

This is more an RFC than a patch.
This is the huawei_cdc_ncm driver skeleton - it handles the embedded AT channel 
on my device, and is stable upon usage, installing and removal.
The wwan interface is not functional - and surely there are lots of errors!

Signed-off-by: Enrico Mioso <mrkiko.rs@...il.com>

diff --git a/drivers/net/usb/huawei_cdc_ncm.c b/drivers/net/usb/huawei_cdc_ncm.c
new file mode 100644
index 0000000..2e76c87
--- /dev/null
+++ b/drivers/net/usb/huawei_cdc_ncm.c
@@ -0,0 +1,239 @@
+/*
+ * huawei_cdc_ncm.c - handles hawei-style NCM devices.
+ * Copyright (C) Enrico Mioso <mrkiko.rs@...il.com>
+ * This driver handles devices resembling the CDC NCM standard, but 
+ * encapsulating another protocl inside it. An example are some Huawei modems.
+ * This code is based on the original cdc_ncm implementation, that is:
+ * Copyright (C) ST-Ericsson 2010-2012
+ * Contact: Alexey Orishko <alexey.orishko@...ricsson.com>
+ * Original author: Hans Petter Selasky <hans.petter.selasky@...ricsson.com>
+ *
+ * USB Host Driver for Network Control Model (NCM)
+ * http://www.usb.org/developers/devclass_docs/NCM10.zip
+ *
+ * The NCM encoding, decoding and initialization logic
+ * derives from FreeBSD 8.x. if_cdce.c and if_cdcereg.h
+ *
+ * This software is available to you under a choice of one of two
+ * licenses. You may choose this file to be licensed under the terms
+ * of the GNU General Public License (GPL) Version 2 or the 2-clause
+ * BSD license listed below:
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/ethtool.h>
+#include <linux/if_vlan.h>
+#include <linux/ip.h>
+#include <linux/mii.h>
+#include <linux/usb.h>
+#include <linux/usb/cdc.h>
+#include <linux/usb/usbnet.h>
+#include <linux/usb/cdc-wdm.h>
+#include <linux/usb/cdc_ncm.h>
+
+/* Specific driver data */
+struct huawei_cdc_ncm_state {
+	struct cdc_ncm_ctx *ctx;
+	atomic_t pmcount;
+	struct usb_driver *subdriver;
+	struct usb_interface *control;
+	struct usb_interface *data;
+};
+
+static int huawei_cdc_ncm_manage_power(struct usbnet *usbnet_dev, int on)
+{
+	struct huawei_cdc_ncm_state *drvstate = (void *)&usbnet_dev->data;
+	int rv = 0;
+
+	if ((on && atomic_add_return(1, &drvstate->pmcount) == 1) || (!on && atomic_dec_and_test(&drvstate->pmcount))) {
+		rv = usb_autopm_get_interface(usbnet_dev->intf);
+		if (rv < 0)
+			goto err;
+		usbnet_dev->intf->needs_remote_wakeup = on;
+		usb_autopm_put_interface(usbnet_dev->intf);
+	}
+err:
+	return rv;
+}
+
+static int huawei_cdc_ncm_wdm_manage_power(struct usb_interface *intf, int status)
+{
+	struct usbnet *usbnet_dev = usb_get_intfdata(intf);
+
+	/* can be called while disconnecting */
+	if (!usbnet_dev)
+		return 0;
+
+	return huawei_cdc_ncm_manage_power(usbnet_dev, status);
+}
+
+
+/* Bind our driver to needed interfaces. Heavily inspired by cdc_mbim.c one! */
+static int huawei_cdc_ncm_bind(struct usbnet *usbnet_dev, struct usb_interface *intf) {
+
+	/* Some general use variables */
+	struct cdc_ncm_ctx *ctx;
+	struct usb_driver *subdriver = ERR_PTR(-ENODEV);
+	int ret = -ENODEV;
+	struct huawei_cdc_ncm_state *drvstate = (void *)&usbnet_dev->data;
+	
+	/* Actually binds us to the device: use standard ncm function */
+	ret = cdc_ncm_bind_common(usbnet_dev, intf, 1); /* altsetting should be 1 */
+	
+	/* Did the ncm bind function fail? */
+	if (ret)
+		goto err;
+	
+	/* Let cdc data ctx pointer point to our state structure */
+	ctx = drvstate->ctx;
+	
+	if (usbnet_dev->status) 
+		subdriver = usb_cdc_wdm_register(ctx->control, &usbnet_dev->status->desc, 4096, huawei_cdc_ncm_wdm_manage_power); /* a smarter way to calculate that constant? */
+	if (IS_ERR(subdriver)) {
+	 ret = PTR_ERR(subdriver);
+	 cdc_ncm_unbind(usbnet_dev, intf);
+   goto err;
+	}
+	
+	/* Prevent usbnet from using the status descriptor */
+	usbnet_dev->status = NULL;
+	
+	drvstate->subdriver = subdriver;
+	
+	/* FIXME: should we handle the vlan header in some way? */
+	/* FIXME2: in my opinion we also could not do ARP, hoping somebody can help... */
+err:
+	return ret; /* ret = -ENODEV if not changed in the meanwhile */
+}
+
+static void huawei_cdc_ncm_unbind(struct usbnet *usbnet_dev, struct usb_interface *intf) {
+	struct huawei_cdc_ncm_state *drvstate = (void *)&usbnet_dev->data;
+	struct cdc_ncm_ctx *ctx = drvstate->ctx;
+	
+	/* Bye cdc-wdm! And see you soon! :) */
+	if (drvstate->subdriver && drvstate->subdriver->disconnect)
+		drvstate->subdriver->disconnect(ctx->control);
+	drvstate->subdriver = NULL;
+	
+	/* Unbind from both control and data interface */
+	cdc_ncm_unbind(usbnet_dev, intf);
+}
+
+/* Suspend function - the logic has been taken from cdc_mbim.c directly. */
+static int huawei_cdc_ncm_suspend(struct usb_interface *intf, pm_message_t message)
+{
+	int ret = 0;
+	struct usbnet *usbnet_dev = usb_get_intfdata(intf);
+	struct huawei_cdc_ncm_state *drvstate = (void *)&usbnet_dev->data;
+	struct cdc_ncm_ctx *ctx = drvstate->ctx;
+
+	if (ctx == NULL) {
+		ret = -1;
+		goto error;
+	}
+
+	/*
+	 * Both usbnet_suspend() and subdriver->suspend() MUST return 0
+	 * in system sleep context, otherwise, the resume callback has
+	 * to recover device from previous suspend failure.
+	 */
+	ret = usbnet_suspend(intf, message);
+	if (ret < 0)
+		goto error;
+
+	if (intf == ctx->control && drvstate->subdriver && drvstate->subdriver->suspend)
+		ret = drvstate->subdriver->suspend(intf, message);
+	if (ret < 0)
+		usbnet_resume(intf);
+
+error:
+	return ret;
+}
+
+/* Resume function - logic took completely from huawei_cdc.c */
+static int huawei_cdc_ncm_resume(struct usb_interface *intf)
+{
+	int ret = 0;
+	struct usbnet *usbnet_dev = usb_get_intfdata(intf);
+	struct huawei_cdc_ncm_state *drvstate = (void *)&usbnet_dev->data;
+	struct cdc_ncm_ctx *ctx = drvstate->ctx;
+	bool callsub = (intf == ctx->control && drvstate->subdriver && drvstate->subdriver->resume); /* should we call subdriver's resume? ? */
+
+	if (callsub)
+		ret = drvstate->subdriver->resume(intf);
+	if (ret < 0)
+		goto err;
+	ret = usbnet_resume(intf);
+	if (ret < 0 && callsub && drvstate->subdriver->suspend)
+		drvstate->subdriver->suspend(intf, PMSG_SUSPEND);
+err:
+	return ret;
+}
+
+
+/* General driver informations, exposed partly to modutils */
+static const struct driver_info huawei_cdc_ncm_info = {
+	.description = "Huawei-style CDC NCM",
+	.flags = FLAG_NO_SETINT | FLAG_MULTI_PACKET | FLAG_WWAN,
+	.bind = huawei_cdc_ncm_bind,
+	.unbind = huawei_cdc_ncm_unbind,
+	.manage_power = huawei_cdc_ncm_manage_power,
+	/* NCM RX and TX fixup functions work properly on these devices */
+	.rx_fixup = cdc_ncm_rx_fixup,
+	.tx_fixup = cdc_ncm_tx_fixup,
+};
+
+static const struct usb_device_id huawei_cdc_ncm_devs[] = {
+	/* The correct NCM handling will be implemented. For now, only my dongle
+		will be handled.
+		*/
+	{ USB_DEVICE_INTERFACE_NUMBER(0x12d1, 0x1506, 1), \
+		.driver_info = (unsigned long)&huawei_cdc_ncm_info,
+	},
+
+	{
+		/* Terminating entry */
+	},
+};
+/* Expose table in module info */
+MODULE_DEVICE_TABLE(usb, huawei_cdc_ncm_devs);
+
+
+/* USB driver struct - used by USB stack */
+static struct usb_driver huawei_cdc_ncm_driver = {
+	.name = "huawei_cdc_ncm",
+	.id_table = huawei_cdc_ncm_devs,
+	.probe = usbnet_probe,
+	.disconnect = usbnet_disconnect,
+	.suspend = huawei_cdc_ncm_suspend,
+	.resume = huawei_cdc_ncm_resume,
+	.reset_resume = huawei_cdc_ncm_resume,
+	.supports_autosuspend = 1,
+	.disable_hub_initiated_lpm = 1,
+};
+module_usb_driver(huawei_cdc_ncm_driver);
+MODULE_AUTHOR("Enrico Mioso <mrkiko.rs@...il.com>");
+MODULE_DESCRIPTION("USB CDC NCM host driver with encapsulated protocol support");
+MODULE_LICENSE("GPL");

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