[RFCv2 08/13] net: usb: usbnet: allow drivers to specify private space needed

[Oliver Neukum <oneukum@suse.com>]

usbnet has been providing a fixed space of unsigned long[5]
for minidrivers. This has led to various constructions in drivers
this is not enough space for.
Allow minidrivers to tell usbnet how much they need by means
of struct driver_info. For backwards compatibility zero
is taken to mean enough space for unsigned long[5]

Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/net/usb/qmi_wwan.c   | 3 ---
 drivers/net/usb/sierra_net.c | 3 ---
 drivers/net/usb/usbnet.c     | 5 ++++-
 include/linux/usb/usbnet.h   | 6 +++++-
 4 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
index 3a4985b582cb..fc2591ccb682 100644
--- a/drivers/net/usb/qmi_wwan.c
+++ b/drivers/net/usb/qmi_wwan.c
@@ -753,9 +753,6 @@ static int qmi_wwan_bind(struct usbnet *dev, struct usb_interface *intf)
 	struct qmi_wwan_state *info = (void *)&dev->data;
 	struct usb_cdc_parsed_header hdr;
 
-	BUILD_BUG_ON((sizeof(((struct usbnet *)0)->data) <
-		      sizeof(struct qmi_wwan_state)));
-
 	/* set up initial state */
 	info->control = intf;
 	info->data = intf;
diff --git a/drivers/net/usb/sierra_net.c b/drivers/net/usb/sierra_net.c
index 4d3ed642b3e7..5a32796a7a89 100644
--- a/drivers/net/usb/sierra_net.c
+++ b/drivers/net/usb/sierra_net.c
@@ -855,9 +855,6 @@ static struct sk_buff *sierra_net_tx_fixup(struct usbnet *dev,
 	u16 len;
 	bool need_tail;
 
-	BUILD_BUG_ON(sizeof_field(struct usbnet, data)
-				< sizeof(struct cdc_state));
-
 	dev_dbg(&dev->udev->dev, "%s", __func__);
 	if (priv->link_up && check_ethip_packet(skb, dev) && is_ip(skb)) {
 		/* enough head room as is? */
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 8a9e0d98d9c6..b3cc3428b342 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1734,6 +1734,7 @@ usbnet_probe(struct usb_interface *udev, const struct usb_device_id *prod)
 	int				status;
 	const char			*name;
 	struct usb_driver 	*driver = to_usb_driver(udev->dev.driver);
+	unsigned int extra;
 
 	/* usbnet already took usb runtime pm, so have to enable the feature
 	 * for usb interface, otherwise usb_autopm_get_interface may return
@@ -1756,7 +1757,9 @@ usbnet_probe(struct usb_interface *udev, const struct usb_device_id *prod)
 	status = -ENOMEM;
 
 	// set up our own records
-	net = alloc_etherdev(sizeof(*dev));
+	extra = info->required_room ?
+		info->required_room : 5 * sizeof(unsigned long);
+	net = alloc_etherdev(sizeof(*dev) + extra);
 	if (!net)
 		goto out;
 
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index 766862427620..41582346360f 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -50,7 +50,6 @@ struct usbnet {
 	struct net_device	*net;
 	int			msg_enable;
 	struct cdc_state	cdc;		/* too common to leave out*/
-	unsigned long		data[5];
 	u32			xid;
 	u32			hard_mtu;	/* count any extra framing */
 	size_t			rx_urb_size;	/* size for rx urbs */
@@ -93,6 +92,8 @@ struct usbnet {
  * that must be broken
  */
 #		define EVENT_UNPLUG		31
+
+	DECLARE_FLEX_ARRAY(unsigned long, data);
 };
 
 static inline bool usbnet_going_away(struct usbnet *ubn)
@@ -142,6 +143,9 @@ struct driver_info {
 #define FLAG_RX_ASSEMBLE	0x4000	/* rx packets may span >1 frames */
 #define FLAG_NOARP		0x8000	/* device can't do ARP */
 
+	/* tells us how much private space is need in the descriptor */
+	unsigned int	required_room;
+
 	/* init device ... can sleep, or cause probe() failure */
 	int	(*bind)(struct usbnet *, struct usb_interface *);
 
-- 
2.53.0