[RFC 0/3] caif: Add support for CAIF over CDC NCM USB interface

[RFC 0/3] caif: Add support for CAIF over CDC NCM USB interface

[Sjur Br��ndeland]

From: Sjur Brændeland <sjur.brandeland@stericsson.com>

The following patches enables sending and receive CAIF packets
over a cdc_ncm usb interface.

The patches has been tested on real HW and we have been running with this
for more than 6 months now.

NCM 1.0 does not support anything but Ethernet framing, hence
CAIF payload will be put into Ethernet frames. This it's a little
quirky, the long term solution for NCM should be based on
MBIM 1.0 specification.

These patches applies on top of previous patch-set:
commit 1014df0d3589ffc5dc881d0ca45164a482a55574
"Remove unused enum cfcnfg_phy_type and the parameter to cfserl_create."

Review comments and feedback is welcome.

Thanks,
Sjur Brændeland

Sjur Brændeland (3):
  caif: Add support for flow-control on device's tx-queue
  if_ether.h: Add IEEE 802.1 Local Experimental Ethertype 1.
  caif: Add support for CAIF over CDC NCM USB interface

 include/linux/if_ether.h  |    1 +
 include/net/caif/cfusbl.h |   13 +++
 net/caif/Kconfig          |   11 +++
 net/caif/Makefile         |    4 +-
 net/caif/caif_dev.c       |   55 +++++++++++++
 net/caif/cfusbl.c         |  199 +++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 282 insertions(+), 1 deletions(-)
 create mode 100644 include/net/caif/cfusbl.h
 create mode 100644 net/caif/cfusbl.c

[RFC 1/3] caif: Add support for flow-control on device's tx-queue

[Sjur Br��ndeland]

From: Sjur Brændeland <sjur.brandeland@stericsson.com>

Flow control is implemented by inspecting the qdisc queue length
in order to detect potential overflow on the TX queue. When a threshold
is reached flow-off is sent upwards in the CAIF stack. At the same time
the skb->destructor is hi-jacked in order to detect when the last packet
put on queue is consumed. When this "hi-jacked" packet is consumed, flow-on
is sent upwards in the CAIF stack.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
---
 net/caif/caif_dev.c |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 48 insertions(+), 0 deletions(-)

diff --git a/net/caif/caif_dev.c b/net/caif/caif_dev.c
index f7e8c70..415353e 100644
--- a/net/caif/caif_dev.c
+++ b/net/caif/caif_dev.c
@@ -34,6 +34,7 @@ struct caif_device_entry {
 	struct list_head list;
 	struct net_device *netdev;
 	int __percpu *pcpu_refcnt;
+	bool xoff;
 };
 
 struct caif_device_entry_list {
@@ -48,6 +49,7 @@ struct caif_net {
 };
 
 static int caif_net_id;
+static int q_high = 50; /* Percent */
 
 struct cfcnfg *get_cfcnfg(struct net *net)
 {
@@ -126,9 +128,28 @@ static struct caif_device_entry *caif_get(struct net_device *dev)
 	return NULL;
 }
 
+void caif_flow_cb(struct sk_buff *skb)
+{
+	struct caif_device_entry *caifd;
+	WARN_ON(skb->dev == NULL);
+
+	rcu_read_lock();
+	caifd = caif_get(skb->dev);
+	caifd->xoff = 0;
+	caifd_hold(caifd);
+	rcu_read_unlock();
+
+	caifd->layer.up->
+		ctrlcmd(caifd->layer.up,
+			_CAIF_CTRLCMD_PHYIF_FLOW_ON_IND,
+			caifd->layer.id);
+	caifd_put(caifd);
+}
+
 static int transmit(struct cflayer *layer, struct cfpkt *pkt)
 {
 	int err;
+	struct caif_dev_common *caifdev;
 	struct caif_device_entry *caifd =
 	    container_of(layer, struct caif_device_entry, layer);
 	struct sk_buff *skb;
@@ -137,6 +158,33 @@ static int transmit(struct cflayer *layer, struct cfpkt *pkt)
 	skb->dev = caifd->netdev;
 	skb_reset_network_header(skb);
 	skb->protocol = htons(ETH_P_CAIF);
+	caifdev = netdev_priv(caifd->netdev);
+
+	if (caifdev->flowctrl == NULL && caifd->netdev->tx_queue_len > 0 &&
+			!caifd->xoff) {
+		struct netdev_queue *txq;
+		int high;
+
+		txq = netdev_get_tx_queue(skb->dev, 0);
+		high = (caifd->netdev->tx_queue_len * q_high) / 100;
+
+		/* If we run with a TX queue, check if the queue is too long*/
+		if (netif_queue_stopped(caifd->netdev) ||
+			qdisc_qlen(txq->qdisc) > high) {
+
+			pr_debug("queue stop(%d) or full (%d>%d) - XOFF\n",
+					netif_queue_stopped(caifd->netdev),
+					qdisc_qlen(txq->qdisc), high);
+			caifd->xoff = 1;
+			/* Hijack this skb free callback function. */
+			skb_orphan(skb);
+			skb->destructor = caif_flow_cb;
+			caifd->layer.up->
+				ctrlcmd(caifd->layer.up,
+					_CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
+					caifd->layer.id);
+		}
+	}
 
 	err = dev_queue_xmit(skb);
 	if (err > 0)
-- 
1.7.0.4

[RFC 2/3] if_ether.h: Add IEEE 802.1 Local Experimental Ethertype 1.

[Sjur Br��ndeland]

From: Sjur Brændeland <sjur.brandeland@stericsson.com>

Add EthType 0x88b5.
This Ethertype value is available for public use for prototype and
vendor-specific protocol development,as defined in Amendment 802a
to IEEE Std 802.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
---
 include/linux/if_ether.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/include/linux/if_ether.h b/include/linux/if_ether.h
index e473003..56d907a 100644
--- a/include/linux/if_ether.h
+++ b/include/linux/if_ether.h
@@ -79,6 +79,7 @@
 #define ETH_P_PAE	0x888E		/* Port Access Entity (IEEE 802.1X) */
 #define ETH_P_AOE	0x88A2		/* ATA over Ethernet		*/
 #define ETH_P_8021AD	0x88A8          /* 802.1ad Service VLAN		*/
+#define ETH_P_802_EX1	0x88B5		/* 802.1 Local Experimental 1.  */
 #define ETH_P_TIPC	0x88CA		/* TIPC 			*/
 #define ETH_P_8021AH	0x88E7          /* 802.1ah Backbone Service Tag */
 #define ETH_P_1588	0x88F7		/* IEEE 1588 Timesync */
-- 
1.7.0.4

[RFC 3/3] caif: Add support for CAIF over CDC NCM USB interface

[Sjur Br��ndeland]

From: Sjur Brændeland <sjur.brandeland@stericsson.com>

NCM 1.0 does not support anything but Ethernet framing, hence
CAIF payload will be put into Ethernet frames.

Discovery is based on fixed USB vendor 0x04cc (ST-Ericsson),
product-id 0x230f (NCM). In this variant only CAIF payload is sent over
the NCM interface.

The CAIF stack (cfusbl.c) will when USB registers first check if
we got a CDC NCM USB interface with the right VID, PID.
It will then read the device's Ethernet address and create a 'template'
Ethernet TX header, using a broadcast address as the destination address,
and EthType 0x88b5 (802.1 Local Experimental - vendor specific).

A protocol handler for 0x88b5 is setup for reception of CAIF frames from
the CDC NCM USB interface.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
---
 include/net/caif/cfusbl.h |   13 +++
 net/caif/Kconfig          |   11 +++
 net/caif/Makefile         |    4 +-
 net/caif/caif_dev.c       |    7 ++
 net/caif/cfusbl.c         |  199 +++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 233 insertions(+), 1 deletions(-)
 create mode 100644 include/net/caif/cfusbl.h
 create mode 100644 net/caif/cfusbl.c

diff --git a/include/net/caif/cfusbl.h b/include/net/caif/cfusbl.h
new file mode 100644
index 0000000..7ef2499
--- /dev/null
+++ b/include/net/caif/cfusbl.h
@@ -0,0 +1,13 @@
+/*
+ * Copyright (C) ST-Ericsson AB 2010
+ * Author:	Sjur Brendeland/sjur.brandeland@stericsson.com
+ * License terms: GNU General Public License (GPL) version 2
+ */
+
+#ifndef CFUSBL_H_
+#define CFUSBL_H_
+
+void cfusbl_init(void);
+void cfusbl_exit(void);
+
+#endif				/* CFUSBL_H_ */
diff --git a/net/caif/Kconfig b/net/caif/Kconfig
index 529750d..43cd844 100644
--- a/net/caif/Kconfig
+++ b/net/caif/Kconfig
@@ -40,3 +40,14 @@ config CAIF_NETDEV
 	If you select to build it as a built-in then the main CAIF device must
 	also be a built-in.
 	If unsure say Y.
+
+config CAIF_USB
+	bool "CAIF USB support"
+	depends on CAIF
+	default CAIF
+	---help---
+	Say Y if you are using CAIF over USB CDC NCM.
+	This can be either built-in or a loadable module,
+	If you select to build it as a built-in then the main CAIF device must
+	also be a built-in.
+	If unsure say N.
diff --git a/net/caif/Makefile b/net/caif/Makefile
index ebcd4e7..3965f73 100644
--- a/net/caif/Makefile
+++ b/net/caif/Makefile
@@ -1,4 +1,5 @@
-ccflags-$(CONFIG_CAIF_DEBUG)     :=      -DDEBUG
+ccflags-$(CONFIG_CAIF_DEBUG) += -DDEBUG
+ccflags-$(CONFIG_CAIF_USB) += -DCAIF_USB
 
 caif-y := caif_dev.o \
 	cfcnfg.o cfmuxl.o cfctrl.o  \
@@ -6,6 +7,7 @@ caif-y := caif_dev.o \
 	cfserl.o cfdgml.o  \
 	cfrfml.o cfvidl.o cfutill.o \
 	cfsrvl.o cfpkt_skbuff.o
+caif-$(CONFIG_CAIF_USB) += cfusbl.o
 
 obj-$(CONFIG_CAIF) += caif.o
 obj-$(CONFIG_CAIF_NETDEV) += chnl_net.o
diff --git a/net/caif/caif_dev.c b/net/caif/caif_dev.c
index 415353e..6ef0e90 100644
--- a/net/caif/caif_dev.c
+++ b/net/caif/caif_dev.c
@@ -25,6 +25,7 @@
 #include <net/caif/cfpkt.h>
 #include <net/caif/cfcnfg.h>
 #include <net/caif/cfserl.h>
+#include <net/caif/cfusbl.h>
 
 MODULE_LICENSE("GPL");
 
@@ -506,6 +507,9 @@ static int __init caif_device_init(void)
 	if (result)
 		return result;
 
+#ifdef CAIF_USB
+	cfusbl_init();
+#endif
 	register_netdevice_notifier(&caif_device_notifier);
 	dev_add_pack(&caif_packet_type);
 
@@ -517,6 +521,9 @@ static void __exit caif_device_exit(void)
 	unregister_pernet_device(&caif_net_ops);
 	unregister_netdevice_notifier(&caif_device_notifier);
 	dev_remove_pack(&caif_packet_type);
+#ifdef CAIF_USB
+	cfusbl_exit();
+#endif
 }
 
 module_init(caif_device_init);
diff --git a/net/caif/cfusbl.c b/net/caif/cfusbl.c
new file mode 100644
index 0000000..8353a55
--- /dev/null
+++ b/net/caif/cfusbl.c
@@ -0,0 +1,199 @@
+/*
+ * CAIF USB handler
+ * Copyright (C) ST-Ericsson AB 2011
+ * Author:	Sjur Brendeland/sjur.brandeland@stericsson.com
+ * License terms: GNU General Public License (GPL) version 2
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__
+
+#include <linux/netdevice.h>
+#include <linux/slab.h>
+#include <linux/netdevice.h>
+#include <linux/mii.h>
+#include <linux/usb.h>
+#include <linux/usb/usbnet.h>
+#include <net/netns/generic.h>
+#include <net/caif/caif_dev.h>
+#include <net/caif/caif_layer.h>
+#include <net/caif/cfpkt.h>
+#include <net/caif/cfcnfg.h>
+
+MODULE_LICENSE("GPL");
+
+#define CFUSB_PAD_DESCR_SZ 1	/* Alignment descriptor length */
+#define CFUSB_ALIGNMENT 4	/* Number of bytes to align. */
+#define CFUSB_MAX_HEADLEN (CFUSB_PAD_DESCR_SZ + CFUSB_ALIGNMENT-1)
+#define STE_USB_VID 0x04cc	/* USB Product ID for ST-Ericsson */
+#define STE_USB_PID_CAIF 0x2306	/* Product id for CAIF Modems */
+
+struct cfusbl {
+	struct cflayer layer;
+	u8 tx_eth_hdr[ETH_HLEN];
+};
+
+static bool pack_added;
+
+static int cfusbl_receive(struct cflayer *layr, struct cfpkt *pkt)
+{
+	u8 hpad;
+
+	/* Remove padding. */
+	cfpkt_extr_head(pkt, &hpad, 1);
+	cfpkt_extr_head(pkt, NULL, hpad);
+	return layr->up->receive(layr->up, pkt);
+}
+
+static int cfusbl_transmit(struct cflayer *layr, struct cfpkt *pkt)
+{
+	struct caif_payload_info *info;
+	u8 hpad;
+	u8 zeros[CFUSB_ALIGNMENT];
+	struct sk_buff *skb;
+	struct cfusbl *usbl = container_of(layr, struct cfusbl, layer);
+
+	skb = cfpkt_tonative(pkt);
+
+	skb_reset_network_header(skb);
+	skb->protocol = htons(ETH_P_IP);
+
+	info = cfpkt_info(pkt);
+	hpad = (info->hdr_len + CFUSB_PAD_DESCR_SZ) & (CFUSB_ALIGNMENT - 1);
+
+	if (skb_headroom(skb) < ETH_HLEN + CFUSB_PAD_DESCR_SZ + hpad) {
+		pr_warn("Headroom to small\n");
+		kfree_skb(skb);
+		return -EIO;
+	}
+	memset(zeros, 0, hpad);
+
+	cfpkt_add_head(pkt, zeros, hpad);
+	cfpkt_add_head(pkt, &hpad, 1);
+	cfpkt_add_head(pkt, usbl->tx_eth_hdr, sizeof(usbl->tx_eth_hdr));
+	return layr->dn->transmit(layr->dn, pkt);
+}
+
+static void cfusbl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
+					int phyid)
+{
+	if (layr->up && layr->up->ctrlcmd)
+		layr->up->ctrlcmd(layr->up, ctrl, layr->id);
+}
+
+struct cflayer *cfusbl_create(int phyid, u8 ethaddr[ETH_ALEN],
+					u8 braddr[ETH_ALEN])
+{
+	struct cfusbl *this = kmalloc(sizeof(struct cfusbl), GFP_ATOMIC);
+
+	if (!this) {
+		pr_warn("Out of memory\n");
+		return NULL;
+	}
+	caif_assert(offsetof(struct cfusbl, layer) == 0);
+
+	memset(this, 0, sizeof(struct cflayer));
+	this->layer.receive = cfusbl_receive;
+	this->layer.transmit = cfusbl_transmit;
+	this->layer.ctrlcmd = cfusbl_ctrlcmd;
+	snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "usb%d", phyid);
+	this->layer.id = phyid;
+
+	/*
+	 * Construct TX ethernet header:
+	 *	0-5	destination address
+	 *	5-11	source address
+	 *	12-13	protocol type
+	 */
+	memcpy(&this->tx_eth_hdr[ETH_ALEN], braddr, ETH_ALEN);
+	memcpy(&this->tx_eth_hdr[ETH_ALEN], ethaddr, ETH_ALEN);
+	this->tx_eth_hdr[12] = cpu_to_be16(ETH_P_802_EX1) & 0xff;
+	this->tx_eth_hdr[13] = (cpu_to_be16(ETH_P_802_EX1) >> 8) & 0xff;
+	pr_debug("caif ethernet TX-header dst:%pM src:%pM type:%02x%02x\n",
+			this->tx_eth_hdr, this->tx_eth_hdr + ETH_ALEN,
+			this->tx_eth_hdr[12], this->tx_eth_hdr[13]);
+
+	return (struct cflayer *) this;
+}
+
+static struct packet_type caif_usb_type __read_mostly = {
+	.type = cpu_to_be16(ETH_P_802_EX1),
+};
+
+static int cfusbl_device_notify(struct notifier_block *me, unsigned long what,
+			      void *arg)
+{
+	struct net_device *dev = arg;
+	struct caif_dev_common common;
+	struct cflayer *layer, *link_support;
+	struct usbnet	*usbnet = netdev_priv(dev);
+	struct usb_device	*usbdev = usbnet->udev;
+	struct ethtool_drvinfo drvinfo;
+
+	if (what != NETDEV_REGISTER)
+		return 0;
+	/*
+	 * Quirks: High-jack ethtool to find if we have a NCM device,
+	 * and find it's VID/PID.
+	 */
+	if (dev->ethtool_ops == NULL || dev->ethtool_ops->get_drvinfo == NULL)
+		return 0;
+
+	dev->ethtool_ops->get_drvinfo(dev, &drvinfo);
+	if (strncmp(drvinfo.driver, "cdc_ncm", 7) != 0)
+		return 0;
+
+	pr_debug("USB CDC NCM device VID:0x%4x PID:0x%4x\n",
+		le16_to_cpu(usbdev->descriptor.idVendor),
+		le16_to_cpu(usbdev->descriptor.idProduct));
+
+	/* Check for VID/PID that supports CAIF */
+	if (!(le16_to_cpu(usbdev->descriptor.idVendor) == STE_USB_VID &&
+		le16_to_cpu(usbdev->descriptor.idProduct) == STE_USB_PID_CAIF))
+		return 0;
+
+	memset(&common, 0, sizeof(common));
+	common.use_frag = false;
+	common.use_fcs = false;
+	common.use_stx = false;
+	common.link_select = CAIF_LINK_HIGH_BANDW;
+	common.flowctrl = NULL;
+
+	link_support = cfusbl_create(dev->ifindex, dev->dev_addr,
+					dev->broadcast);
+	if (!link_support) {
+		pr_warn("Out of memory\n");
+		return -ENOMEM;
+	}
+
+	if (dev->num_tx_queues > 1)
+		pr_warn("USB device uses more than one tx queue\n");
+
+	caif_enroll_dev(dev, &common, link_support, CFUSB_MAX_HEADLEN,
+			&layer, &caif_usb_type.func);
+	if (!pack_added)
+		dev_add_pack(&caif_usb_type);
+	pack_added = 1;
+
+	strncpy(layer->name, dev->name,
+			sizeof(layer->name) - 1);
+	layer->name[sizeof(layer->name) - 1] = 0;
+
+	return 0;
+}
+
+static struct notifier_block caif_device_notifier = {
+	.notifier_call = cfusbl_device_notify,
+	.priority = 0,
+};
+
+void cfusbl_init(void)
+{
+	register_netdevice_notifier(&caif_device_notifier);
+}
+
+void cfusbl_exit(void)
+{
+	unregister_netdevice_notifier(&caif_device_notifier);
+	dev_remove_pack(&caif_usb_type);
+}
-- 
1.7.0.4

Re: [RFC 2/3] if_ether.h: Add IEEE 802.1 Local Experimental Ethertype 1.

[Rémi Denis-Courmont]

On Wed, 30 Nov 2011 21:44:05 +0100, Sjur Br��ndeland
<sjur.brandeland@stericsson.com> wrote:
> From: Sjur Brændeland <sjur.brandeland@stericsson.com>
> 
> Add EthType 0x88b5.
> This Ethertype value is available for public use for prototype and
> vendor-specific protocol development,as defined in Amendment 802a
> to IEEE Std 802.

I don't think you can just go and steal a reserved EtherType. What if some
user-space (using packet sockets) or out-of-tree kernel driver does actual
"experiment" with this type?

Why don't you define your own link-layer, e.g. with a vendor-specific CDC
profile?

-- 
Rémi Denis-Courmont
http://www.remlab.net/

Re: [RFC 2/3] if_ether.h: Add IEEE 802.1 Local Experimental Ethertype 1.

[Sjur Brændeland]

Hi Rémi,

>> Add EthType 0x88b5.
>> This Ethertype value is available for public use for prototype and
>> vendor-specific protocol development,as defined in Amendment 802a
>> to IEEE Std 802.
>
> I don't think you can just go and steal a reserved EtherType. What if some
> user-space (using packet sockets) or out-of-tree kernel driver does actual
> "experiment" with this type?

I don't think defining this type in if_ether.h would harm anyone ;-)

I think your comments are applicable for the patch:
"caif: Add support for CAIF over CDC NCM USB interface".

Currently CAIF over CDC NCM USB is only deployed for the Ethernet link
between Host and Modem internally in a Smart Phone, and not out of the
Smart Phone (Tethering). The modem's Ethernet interface is connected to
the CAIF stack and not to the modem's IP stack.On the Linux Host,
CAIF takes this EthType into use *only* for a Ethernet interface with
the VID/PID of a ST-E CAIF modem.

With this setup I have a hard time seeing the big risk of interference with
others using this Ethernet Type.

We use Ethernet for this point-to-point link because  NCM 1.0 only
defines Ethernet as the only bearer. The long term solution for CAIF over
NCM should be based on MBIM 1.0 specification, where vendor specific
services can be define. We could then transmit CAIF frames directly
in a vendor specific service without the use of a Ethernet header.

> Why don't you define your own link-layer, e.g. with a vendor-specific CDC
> profile?
I look into this...

BTW: Could you please do "reply-all" next time, so I get your mail in my inbox.

Regards,
Sjur

Re: [RFC 2/3] if_ether.h: Add IEEE 802.1 Local Experimental Ethertype 1.

[Rémi Denis-Courmont]

On Mon, 5 Dec 2011 14:14:30 +0100, Sjur Brændeland <sjurbren@gmail.com>
wrote:
>> I don't think you can just go and steal a reserved EtherType. What if
>> some user-space (using packet sockets) or out-of-tree kernel driver
>> does actual "experiment" with this type?
> 
> I don't think defining this type in if_ether.h would harm anyone ;-)
> 
> I think your comments are applicable for the patch:
> "caif: Add support for CAIF over CDC NCM USB interface".

That patch makes no sense without this patch. I comment on the first patch
in the series that exhibits the problem.

> Currently CAIF over CDC NCM USB is only deployed for the Ethernet link
> between Host and Modem internally in a Smart Phone, and not out of the
> Smart Phone (Tethering). The modem's Ethernet interface is connected to
> the CAIF stack and not to the modem's IP stack.On the Linux Host,
> CAIF takes this EthType into use *only* for a Ethernet interface with
> the VID/PID of a ST-E CAIF modem.

It's even weirder then. If you have control over both ends and the NCM 1.0
interface is not adequate, then you really should use your own CDC class
for the purpose.

-- 
Rémi Denis-Courmont
http://www.remlab.net/

Re: [RFC 2/3] if_ether.h: Add IEEE 802.1 Local Experimental Ethertype 1.

[Sjur Brændeland]

Hi Rémi,
> It's even weirder then. If you have control over both ends and the NCM 1.0
> interface is not adequate, then you really should use your own CDC class
> for the purpose.

The reason we use NCM is performance: CDC normally gives less than 100Mbps,
while NCM can give you up to 200Mbps.

Regards,
Sjur

Re: [RFC 2/3] if_ether.h: Add IEEE 802.1 Local Experimental Ethertype 1.

[Rémi Denis-Courmont]

Le lundi 5 décembre 2011 16:33:50 Sjur Brændeland, vous avez écrit :
> Hi Rémi,
> 
> > It's even weirder then. If you have control over both ends and the NCM
> > 1.0 interface is not adequate, then you really should use your own CDC
> > class for the purpose.
> 
> The reason we use NCM is performance: CDC normally gives less than 100Mbps,
> while NCM can give you up to 200Mbps.

NCM is a sub-profile of CDC, so that statement makes no sense to me.

-- 
Rémi Denis-Courmont
http://www.remlab.net/
http://fi.linkedin.com/in/remidenis