[14/29] i2400m: linkage to the networking stack

diff --git a/drivers/net/wimax/i2400m/netdev.c b/drivers/net/wimax/i2400m/netdev.c
new file mode 100644
index 0000000..63fe708
--- /dev/null
+++ b/drivers/net/wimax/i2400m/netdev.c
@@ -0,0 +1,524 @@ 
+/*
+ * Intel Wireless WiMAX Connection 2400m
+ * Glue with the networking stack
+ *
+ *
+ * Copyright (C) 2007 Intel Corporation <linux-wimax@intel.com>
+ * Yanir Lubetkin <yanirx.lubetkin@intel.com>
+ * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ *
+ * This implements an ethernet device for the i2400m.
+ *
+ * We fake being an ethernet device to simplify the support from user
+ * space and from the other side. The world is (sadly) configured to
+ * take in only Ethernet devices...
+ *
+ * Because of this, currently there is an copy-each-rxed-packet
+ * overhead on the RX path. Each IP packet has to be reallocated to
+ * add an ethernet header (as there is no space in what we get from
+ * the device). This is a known drawback and coming versions of the
+ * device's firmware are being changed to add header space that can be
+ * used to insert the ethernet header without having to reallocate and
+ * copy.
+ *
+ * TX error handling is tricky; because we have to FIFO/queue the
+ * buffers for transmission (as the hardware likes it aggregated), we
+ * just give the skb to the TX subsystem and by the time it is
+ * transmitted, we have long forgotten about it. So we just don't care
+ * too much about it.
+ *
+ * Note that when the device is in idle mode with the basestation, we
+ * need to negotiate coming back up online. That involves negotiation
+ * and possible user space interaction. Thus, we defer to a workqueue
+ * to do all that. By default, we only queue a single packet and drop
+ * the rest, as potentially the time to go back from idle to normal is
+ * long.
+ *
+ * ROADMAP
+ *
+ * i2400m_open         Called on ifconfig up
+ * i2400m_stop         Called on ifconfig down
+ *
+ * i2400m_hard_start_xmit Called by the network stack to send a packet
+ *   i2400m_net_wake_tx	  Wake up device from basestation-IDLE & TX
+ *     i2400m_wake_tx_work
+ *       i2400m_cmd_exit_idle
+ *       i2400m_tx
+ *   i2400m_net_tx        TX a data frame
+ *     i2400m_tx
+ *
+ * i2400m_change_mtu      Called on ifconfig mtu XXX
+ *
+ * i2400m_tx_timeout      Called when the device times out
+ *
+ * i2400m_net_rx          Called by the RX code when a data frame is
+ *                        available.
+ * i2400m_netdev_setup    Called to setup all the netdev stuff from
+ *                        alloc_netdev.
+ */
+#include <linux/if_arp.h>
+#include <linux/netdevice.h>
+#include "i2400m.h"
+
+
+#define D_SUBMODULE netdev
+#include "debug-levels.h"
+
+enum {
+/* netdev interface */
+	/*
+	 * Out of NWG spec (R1_v1.2.2), 3.3.3 ASN Bearer Plane MTU Size
+	 *
+	 * The MTU is 1400 or less
+	 */
+	I2400M_MAX_MTU = 1400,
+	I2400M_TX_TIMEOUT = HZ,
+	I2400M_TX_QLEN = 5,
+};
+
+
+static
+int i2400m_open(struct net_device *net_dev)
+{
+	int result;
+	struct i2400m *i2400m = net_dev_to_i2400m(net_dev);
+	struct device *dev = i2400m_dev(i2400m);
+
+	d_fnstart(3, dev, "(net_dev %p [i2400m %p])\n", net_dev, i2400m);
+	if (i2400m->ready == 0) {
+		dev_err(dev, "Device is still initializing\n");
+		result = -EBUSY;
+	} else
+		result = 0;
+	d_fnend(3, dev, "(net_dev %p [i2400m %p]) = %d\n",
+		net_dev, i2400m, result);
+	return result;
+}
+
+
+/*
+ *
+ * On kernel versions where cancel_work_sync() didn't return anything,
+ * we rely on wake_tx_skb() being non-NULL.
+ */
+static
+int i2400m_stop(struct net_device *net_dev)
+{
+	struct i2400m *i2400m = net_dev_to_i2400m(net_dev);
+	struct device *dev = i2400m_dev(i2400m);
+
+	d_fnstart(3, dev, "(net_dev %p [i2400m %p])\n", net_dev, i2400m);
+	/* See i2400m_hard_start_xmit(), references are taken there
+	 * and here we release them if the work was still
+	 * pending. Note we can't differentiate work not pending vs
+	 * never scheduled, so the NULL check does that. */
+	if (cancel_work_sync(&i2400m->wake_tx_ws) == 0
+	    && i2400m->wake_tx_skb != NULL) {
+		unsigned long flags;
+		struct sk_buff *wake_tx_skb;
+		spin_lock_irqsave(&i2400m->tx_lock, flags);
+		wake_tx_skb = i2400m->wake_tx_skb;	/* compat help */
+		i2400m->wake_tx_skb = NULL;	/* compat help */
+		spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+		i2400m_put(i2400m);
+		kfree_skb(wake_tx_skb);
+	}
+	d_fnend(3, dev, "(net_dev %p [i2400m %p]) = 0\n", net_dev, i2400m);
+	return 0;
+}
+
+
+/*
+ * Wake up the device and transmit a held SKB, then restart the net queue
+ *
+ * When the device goes into basestation-idle mode, we need to tell it
+ * to exit that mode; it will negotiate with the base station, user
+ * space may have to intervene to rehandshake crypto and then tell us
+ * when it is ready to transmit the packet we have "queued". Still we
+ * need to give it sometime after it reports being ok.
+ *
+ * On error, there is not much we can do. If the error was on TX, we
+ * still wake the queue up to see if the next packet will be luckier.
+ *
+ * If _cmd_exit_idle() fails...well, it could be many things; most
+ * commonly it is that something else took the device out of IDLE mode
+ * (for example, the base station). In that case we get an -EILSEQ and
+ * we are just going to ignore that one. If the device is back to
+ * connected, then fine -- if it is someother state, the packet will
+ * be dropped anyway.
+ */
+void i2400m_wake_tx_work(struct work_struct *ws)
+{
+	int result;
+	struct i2400m *i2400m = container_of(ws, struct i2400m, wake_tx_ws);
+	struct device *dev = i2400m_dev(i2400m);
+	struct sk_buff *skb = i2400m->wake_tx_skb;
+	unsigned long flags;
+
+	spin_lock_irqsave(&i2400m->tx_lock, flags);
+	skb = i2400m->wake_tx_skb;
+	i2400m->wake_tx_skb = NULL;
+	spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+
+	d_fnstart(3, dev, "(ws %p i2400m %p skb %p)\n", ws, i2400m, skb);
+	result = -EINVAL;
+	if (skb == NULL) {
+		dev_err(dev, "WAKE&TX: skb dissapeared!\n");
+		goto out_put;
+	}
+	result = i2400m_cmd_exit_idle(i2400m);
+	if (result == -EILSEQ)
+		result = 0;
+	if (result < 0) {
+		dev_err(dev, "WAKE&TX: device didn't get out of idle: "
+			"%d\n", result);
+			goto error;
+	}
+	result = wait_event_timeout(i2400m->state_wq,
+				    i2400m->state != I2400M_SS_IDLE, 5 * HZ);
+	if (result == 0)
+		result = -ETIMEDOUT;
+	if (result < 0) {
+		dev_err(dev, "WAKE&TX: error waiting for device to exit IDLE: "
+			"%d\n", result);
+		goto error;
+	}
+	msleep(20);	/* device still needs some time or it drops it */
+	result = i2400m_tx(i2400m, skb->data, skb->len, I2400M_PT_DATA);
+	netif_wake_queue(i2400m->wimax_dev.net_dev);
+error:
+	kfree_skb(skb);	/* refcount transferred by _hard_start_xmit() */
+out_put:
+	i2400m_put(i2400m);
+	d_fnend(3, dev, "(ws %p i2400m %p skb %p) = void [%d]\n",
+		ws, i2400m, skb, result);
+}
+
+
+/*
+ * Prepare the data payload TX header
+ *
+ * The i2400m expects a 4 byte header in front of a data packet.
+ *
+ * Because we pretend to be an ethernet device, this packet comes with
+ * an ethernet header. Pull it and push our header.
+ */
+static
+void i2400m_tx_prep_header(struct sk_buff *skb)
+{
+	struct i2400m_pl_data_hdr *pl_hdr;
+	skb_pull(skb, ETH_HLEN);
+	pl_hdr = (struct i2400m_pl_data_hdr *) skb_push(skb, sizeof(*pl_hdr));
+	pl_hdr->reserved = 0;
+}
+
+
+/*
+ * TX an skb to an idle device
+ *
+ * When the device is in basestation-idle mode, we need to wake it up
+ * and then TX. So we queue a work_struct for doing so.
+ *
+ * We need to get an extra ref for the skb (so it is not dropped), as
+ * well as be careful not to queue more than one request (won't help
+ * at all). If more than one request comes or there are errors, we
+ * just drop the packets (see i2400m_hard_start_xmit()).
+ */
+static
+int i2400m_net_wake_tx(struct i2400m *i2400m, struct net_device *net_dev,
+		       struct sk_buff *skb)
+{
+	int result;
+	struct device *dev = i2400m_dev(i2400m);
+	unsigned long flags;
+
+	d_fnstart(3, dev, "(skb %p net_dev %p)\n", skb, net_dev);
+	if (net_ratelimit()) {
+		d_printf(3, dev, "WAKE&NETTX: "
+			 "skb %p sending %d bytes to radio\n",
+			 skb, skb->len);
+		d_dump(4, dev, skb->data, skb->len);
+	}
+	/* We hold a ref count for i2400m and skb, so when
+	 * stopping() the device, we need to cancel that work
+	 * and if pending, release those resources. */
+	result = 0;
+	spin_lock_irqsave(&i2400m->tx_lock, flags);
+	if (!work_pending(&i2400m->wake_tx_ws)) {
+		netif_stop_queue(net_dev);
+		i2400m_get(i2400m);
+		i2400m->wake_tx_skb = skb_get(skb);	/* transfer ref count */
+		i2400m_tx_prep_header(skb);
+		result = schedule_work(&i2400m->wake_tx_ws);
+		WARN_ON(result == 0);
+	}
+	spin_unlock_irqrestore(&i2400m->tx_lock, flags);
+	if (result == 0) {
+		/* Yes, this happens even if we stopped the
+		 * queue -- blame the queue disciplines that
+		 * queue without looking -- I guess there is a reason
+		 * for that. */
+		if (net_ratelimit())
+			d_printf(1, dev, "NETTX: device exiting idle, "
+				 "dropping skb %p, queue running %d\n",
+				 skb, netif_queue_stopped(net_dev));
+		result = -EBUSY;
+	}
+	d_fnend(3, dev, "(skb %p net_dev %p) = %d\n", skb, net_dev, result);
+	return result;
+}
+
+
+/*
+ * Transmit a packet to the base station on behalf of the network stack.
+ *
+ * Returns: 0 if ok, < 0 errno code on error.
+ *
+ * We need to pull the ethernet header and add the hardware header,
+ * which is currently set to all zeroes and reserved.
+ */
+static
+int i2400m_net_tx(struct i2400m *i2400m, struct net_device *net_dev,
+		  struct sk_buff *skb)
+{
+	int result;
+	struct device *dev = i2400m_dev(i2400m);
+
+	d_fnstart(3, dev, "(i2400m %p net_dev %p skb %p)\n",
+		  i2400m, net_dev, skb);
+	/* FIXME: check eth hdr, only IPv4 is routed by the device as of now */
+	net_dev->trans_start = jiffies;
+	i2400m_tx_prep_header(skb);
+	d_printf(3, dev, "NETTX: skb %p sending %d bytes to radio\n",
+		 skb, skb->len);
+	d_dump(4, dev, skb->data, skb->len);
+	result = i2400m_tx(i2400m, skb->data, skb->len, I2400M_PT_DATA);
+	d_fnend(3, dev, "(i2400m %p net_dev %p skb %p) = %d\n",
+		i2400m, net_dev, skb, result);
+	return result;
+}
+
+
+/*
+ * Transmit a packet to the base station on behalf of the network stack
+ *
+ *
+ * Returns: NETDEV_TX_OK (always, even in case of error)
+ *
+ * In case of error, we just drop it. Reasons:
+ *
+ *  - we add a hw header to each skb, and if the network stack
+ *    retries, we have no way to know if that skb has it or not.
+ *
+ *  - network protocols have their own drop-recovery mechanisms
+ *
+ *  - there is not much else we can do
+ *
+ * If the device is idle, we need to wake it up; that is an operation
+ * that will sleep. See i2400m_net_wake_tx() for details.
+ */
+static
+int i2400m_hard_start_xmit(struct sk_buff *skb,
+			   struct net_device *net_dev)
+{
+	int result;
+	struct i2400m *i2400m = net_dev_to_i2400m(net_dev);
+	struct device *dev = i2400m_dev(i2400m);
+
+	d_fnstart(3, dev, "(skb %p net_dev %p)\n", skb, net_dev);
+	if (i2400m->state == I2400M_SS_IDLE)
+		result = i2400m_net_wake_tx(i2400m, net_dev, skb);
+	else
+		result = i2400m_net_tx(i2400m, net_dev, skb);
+	if (result <  0)
+		net_dev->stats.tx_dropped++;
+	else {
+		net_dev->stats.tx_packets++;
+		net_dev->stats.tx_bytes += skb->len;
+	}
+	kfree_skb(skb);
+	result = NETDEV_TX_OK;
+	d_fnend(3, dev, "(skb %p net_dev %p) = %d\n", skb, net_dev, result);
+	return result;
+}
+
+
+static
+int i2400m_change_mtu(struct net_device *net_dev, int new_mtu)
+{
+	int result;
+	struct i2400m *i2400m = net_dev_to_i2400m(net_dev);
+	struct device *dev = i2400m_dev(i2400m);
+
+	if (new_mtu >= I2400M_MAX_MTU) {
+		dev_err(dev, "Cannot change MTU to %d (max is %d)\n",
+			new_mtu, I2400M_MAX_MTU);
+		result = -EINVAL;
+	} else {
+		net_dev->mtu = new_mtu;
+		result = 0;
+	}
+	return result;
+}
+
+
+static
+void i2400m_tx_timeout(struct net_device *net_dev)
+{
+	/*
+	 * We might want to kick the device
+	 *
+	 * There is not much we can do though, as the device requires
+	 * that we send the data aggregated. By the time we receive
+	 * this, there might be data pending to be sent or not...
+	 */
+	net_dev->stats.tx_errors++;
+	return;
+}
+
+
+/*
+ * Create a fake ethernet header
+ *
+ * For emulating an ethernet device, every received IP header has to
+ * be prefixed with an ethernet header.
+ *
+ * What we receive has (potentially) many IP packets concatenated with
+ * no ETH_HLEN bytes prefixed. Thus there is no space for an eth
+ * header.
+ *
+ * We would have to reallocate or do ugly fragment tricks in order to
+ * add it.
+ *
+ * But what we do is use the header space of the RX transaction
+ * (*msg_hdr) as we don't need it anymore; then we'll point all the
+ * data skbs there, as they share the same backing store.
+ *
+ * We only support IPv4 for v3 firmware.
+ */
+static
+void i2400m_rx_fake_eth_header(struct net_device *net_dev,
+			       void *_eth_hdr)
+{
+	struct ethhdr *eth_hdr = _eth_hdr;
+
+	memcpy(eth_hdr->h_dest, net_dev->dev_addr, sizeof(eth_hdr->h_dest));
+	memset(eth_hdr->h_source, 0, sizeof(eth_hdr->h_dest));
+	eth_hdr->h_proto = __constant_cpu_to_be16(ETH_P_IP);
+}
+
+
+/*
+ * i2400m_net_rx - pass a network packet to the stack
+ *
+ * @i2400m: device instance
+ * @skb_rx: the skb where the buffer pointed to by @buf is
+ * @i: 1 if payload is the only one
+ * @buf: pointer to the buffer containing the data
+ * @len: buffer's length
+ *
+ * We just clone the skb and set it up so that it's skb->data pointer
+ * points to "buf" and it's length.
+ *
+ * Note that if the payload is the last (or the only one) in a
+ * multi-payload message, we don't clone the SKB but just reuse it.
+ *
+ * This function is normally run from a thread context. However, we
+ * still use netif_rx() instead of netif_receive_skb() as was
+ * recommended in the mailing list. Reason is in some stress tests
+ * when sending/receiving a lot of data we seem to hit a softlock in
+ * the kernel's TCP implementation [aroudn tcp_delay_timer()]. Using
+ * netif_rx() took care of the issue.
+ *
+ * This is, of course, still open to do more research on why running
+ * with netif_receive_skb() hits this softlock. FIXME.
+ *
+ * FIXME: currently we don't do any efforts at distinguishing if what
+ * we got was an IPv4 or IPv6 header, to setup the protocol field
+ * correctly.
+ */
+void i2400m_net_rx(struct i2400m *i2400m, struct sk_buff *skb_rx,
+		   unsigned i, const void *buf, int buf_len)
+{
+	struct net_device *net_dev = i2400m->wimax_dev.net_dev;
+	struct device *dev = i2400m_dev(i2400m);
+	struct sk_buff *skb;
+
+	d_fnstart(2, dev, "(i2400m %p buf %p buf_len %d)\n",
+		  i2400m, buf, buf_len);
+	if (i) {
+		skb = skb_get(skb_rx);
+		d_printf(2, dev, "RX: reusing first payload skb %p\n", skb);
+		skb_pull(skb, buf - (void *) skb->data);
+		skb_trim(skb, (void *) skb_end_pointer(skb) - buf);
+	} else {
+		/* Yes, this is bad -- a lot of overhead -- see
+		 * comments at the top of the file */
+		skb = __netdev_alloc_skb(net_dev, buf_len, GFP_KERNEL);
+		if (skb == NULL) {
+			dev_err(dev, "NETRX: no memory to realloc skb\n");
+			net_dev->stats.rx_dropped++;
+			goto error_skb_realloc;
+		}
+		memcpy(skb_put(skb, buf_len), buf, buf_len);
+	}
+	i2400m_rx_fake_eth_header(i2400m->wimax_dev.net_dev,
+				  skb->data - ETH_HLEN);
+	skb_set_mac_header(skb, -ETH_HLEN);
+	skb->dev = i2400m->wimax_dev.net_dev;
+	skb->protocol = htons(ETH_P_IP);
+	net_dev->stats.rx_packets++;
+	net_dev->stats.rx_bytes += buf_len;
+	d_printf(3, dev, "NETRX: receiving %d bytes to network stack\n",
+		buf_len);
+	d_dump(4, dev, buf, buf_len);
+	netif_rx_ni(skb);	/* see notes in function header */
+error_skb_realloc:
+	d_fnend(2, dev, "(i2400m %p buf %p buf_len %d) = void\n",
+		i2400m, buf, buf_len);
+}
+
+
+/**
+ * i2400m_netdev_setup - Setup setup @net_dev's i2400m private data
+ *
+ * Called by alloc_netdev()
+ */
+void i2400m_netdev_setup(struct net_device *net_dev)
+{
+	d_fnstart(3, NULL, "(net_dev %p)\n", net_dev);
+	ether_setup(net_dev);
+	net_dev->mtu = I2400M_MAX_MTU;
+	net_dev->tx_queue_len = I2400M_TX_QLEN;
+	net_dev->features =
+		  NETIF_F_VLAN_CHALLENGED
+		| NETIF_F_HIGHDMA;
+	net_dev->flags =
+		IFF_NOARP		/* i2400m is apure IP device */
+		& (~IFF_BROADCAST	/* i2400m is P2P */
+		   & ~IFF_MULTICAST);
+	net_dev->watchdog_timeo = I2400M_TX_TIMEOUT;
+	net_dev->open = i2400m_open;
+	net_dev->stop = i2400m_stop;
+	net_dev->hard_start_xmit = i2400m_hard_start_xmit;
+	net_dev->change_mtu = i2400m_change_mtu;
+	net_dev->tx_timeout = i2400m_tx_timeout;
+	d_fnend(3, NULL, "(net_dev %p) = void\n", net_dev);
+}
+EXPORT_SYMBOL_GPL(i2400m_netdev_setup);
+