Patchwork [RFC] net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards compatibility

login
register
mail settings
Submitter Bjørn Mork
Date March 10, 2013, 6:13 p.m.
Message ID <1362939209-19056-1-git-send-email-bjorn@mork.no>
Download mbox | patch
Permalink /patch/226458/
State RFC
Delegated to: David Miller
Headers show

Comments

Bjørn Mork - March 10, 2013, 6:13 p.m.
Devices implementing NCM backwards compatibility according to section
3.2 of the MBIM v1.0 specification allow either NCM or MBIM on a single
USB function, using different altsettings.  The cdc_ncm and cdc_mbim
drivers will both probe such functions, and must agree on a common
policy for selecting either MBIM or NCM.  Until now, this policy has
been set at build time based on CONFIG_USB_NET_CDC_MBIM.

Use a module parameter to set the system policy at runtime, allowing the
user to prefer NCM on systems with the cdc_mbim driver.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
---

Maybe something like this?  I don't like the way this code looks, but I
am unable to make it look more readable...

Does this still work as expected with all your devices?  Does it allow you
to use cdc_ncm on devices with compatibility mode?  I still don't have any
such device, except for my fake emulated kvm one.

Thanks for testing.


Bjørn

 drivers/net/usb/cdc_mbim.c  |   12 +----------
 drivers/net/usb/cdc_ncm.c   |   49 ++++++++++++++++++++++++++++---------------
 include/linux/usb/cdc_ncm.h |    1 +
 3 files changed, 34 insertions(+), 28 deletions(-)
Bjørn Mork - March 13, 2013, 4:55 p.m.
Bjørn Mork <bjorn@mork.no> writes:

> +#if IS_ENABLED(CONFIG_USB_NET_CDC_MBIM)
> +static bool prefer_mbim = true;
> +#else
> +static bool prefer_mbim;
> +#endif
> +module_param(prefer_mbim, bool, S_IRUGO | S_IWUSR);
> +MODULE_PARM_DESC(prefer_mbim, "Prefer MBIM on NCM/MBIM backwards compatible functions");

So, noone wanting to comment on this? I am not sure how to interpret
that.  If I liked the solution myself I would just have taken it as an
unanimous ack, but I don't...

Please, if your gut feeling is that this is the most stupid thing you've
ever seen, then just say so.  I can take it :)


Bjørn
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/drivers/net/usb/cdc_mbim.c b/drivers/net/usb/cdc_mbim.c
index 248d2dc..70fd7c6 100644
--- a/drivers/net/usb/cdc_mbim.c
+++ b/drivers/net/usb/cdc_mbim.c
@@ -62,24 +62,14 @@  static int cdc_mbim_wdm_manage_power(struct usb_interface *intf, int status)
 	return cdc_mbim_manage_power(dev, status);
 }
 
-
 static int cdc_mbim_bind(struct usbnet *dev, struct usb_interface *intf)
 {
 	struct cdc_ncm_ctx *ctx;
 	struct usb_driver *subdriver = ERR_PTR(-ENODEV);
 	int ret = -ENODEV;
-	u8 data_altsetting = CDC_NCM_DATA_ALTSETTING_NCM;
+	u8 data_altsetting = cdc_ncm_select_altsetting(dev, intf);
 	struct cdc_mbim_state *info = (void *)&dev->data;
 
-	/* see if interface supports MBIM alternate setting */
-	if (intf->num_altsetting == 2) {
-		if (!cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting))
-			usb_set_interface(dev->udev,
-					  intf->cur_altsetting->desc.bInterfaceNumber,
-					  CDC_NCM_COMM_ALTSETTING_MBIM);
-		data_altsetting = CDC_NCM_DATA_ALTSETTING_MBIM;
-	}
-
 	/* Probably NCM, defer for cdc_ncm_bind */
 	if (!cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting))
 		goto err;
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 61b74a2..8b6bd1b 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -55,6 +55,14 @@ 
 
 #define	DRIVER_VERSION				"14-Mar-2012"
 
+#if IS_ENABLED(CONFIG_USB_NET_CDC_MBIM)
+static bool prefer_mbim = true;
+#else
+static bool prefer_mbim;
+#endif
+module_param(prefer_mbim, bool, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(prefer_mbim, "Prefer MBIM on NCM/MBIM backwards compatible functions");
+
 static void cdc_ncm_txpath_bh(unsigned long param);
 static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx);
 static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *hr_timer);
@@ -550,9 +558,12 @@  void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf)
 }
 EXPORT_SYMBOL_GPL(cdc_ncm_unbind);
 
-static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
+/* Select the MBIM altsetting iff it is preferred and available,
+ * returning the number of the corresponding data interface altsetting
+ */
+u8 cdc_ncm_select_altsetting(struct usbnet *dev, struct usb_interface *intf)
 {
-	int ret;
+	struct usb_host_interface *alt;
 
 	/* The MBIM spec defines a NCM compatible default altsetting,
 	 * which we may have matched:
@@ -568,23 +579,27 @@  static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
 	 *   endpoint descriptors, shall be constructed according to
 	 *   the rules given in section 6 (USB Device Model) of this
 	 *   specification."
-	 *
-	 * Do not bind to such interfaces, allowing cdc_mbim to handle
-	 * them
 	 */
-#if IS_ENABLED(CONFIG_USB_NET_CDC_MBIM)
-	if ((intf->num_altsetting == 2) &&
-	    !usb_set_interface(dev->udev,
-			       intf->cur_altsetting->desc.bInterfaceNumber,
-			       CDC_NCM_COMM_ALTSETTING_MBIM)) {
-		if (cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting))
-			return -ENODEV;
-		else
-			usb_set_interface(dev->udev,
-					  intf->cur_altsetting->desc.bInterfaceNumber,
-					  CDC_NCM_COMM_ALTSETTING_NCM);
+	if (prefer_mbim && intf->num_altsetting == 2) {
+		alt = usb_altnum_to_altsetting(intf, CDC_NCM_COMM_ALTSETTING_MBIM);
+		if (alt && cdc_ncm_comm_intf_is_mbim(alt) &&
+		    !usb_set_interface(dev->udev,
+				       intf->cur_altsetting->desc.bInterfaceNumber,
+				       CDC_NCM_COMM_ALTSETTING_MBIM))
+			return CDC_NCM_DATA_ALTSETTING_MBIM;
 	}
-#endif
+	return CDC_NCM_DATA_ALTSETTING_NCM;
+}
+EXPORT_SYMBOL_GPL(cdc_ncm_select_altsetting);
+
+static int cdc_ncm_bind(struct usbnet *dev, struct usb_interface *intf)
+{
+	int ret;
+
+	/* MBIM backwards compatible function? */
+	cdc_ncm_select_altsetting(dev, intf);
+	if (cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting))
+		return -ENODEV;
 
 	/* NCM data altsetting is always 1 */
 	ret = cdc_ncm_bind_common(dev, intf, 1);
diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
index 3b8f9d4..cc25b70 100644
--- a/include/linux/usb/cdc_ncm.h
+++ b/include/linux/usb/cdc_ncm.h
@@ -127,6 +127,7 @@  struct cdc_ncm_ctx {
 	u16 connected;
 };
 
+extern u8 cdc_ncm_select_altsetting(struct usbnet *dev, struct usb_interface *intf);
 extern int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_altsetting);
 extern void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf);
 extern struct sk_buff *cdc_ncm_fill_tx_frame(struct cdc_ncm_ctx *ctx, struct sk_buff *skb, __le32 sign);