commit bd329e1 ("net: cdc_ncm: do not bind to NCM compatible MBIM devices")
introduced a new policy, preferring MBIM for dual NCM/MBIM functions if
the cdc_mbim driver was enabled. This caused a regression for users
wanting to use NCM.
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.
Cc: Greg Suarez <gsuarez@xxxxxxxxxxxxxx>
Cc: Alexey Orishko <alexey.orishko@xxxxxxxxxxxxxx>
Reported-by: Geir Haatveit <nospam@xxxxxxxxxxx>
Reported-by: Tommi Kyntola <kynde@xxxxxxxxx>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=54791
Signed-off-by: Bjørn Mork <bjorn@xxxxxxx>
---
We now have two users independently reporting this as a 3.8 regression,
so something needs to be done. I am not sure if adding a new module
parameter is acceptable for stable, but this problem is definitely a
regression and no other solutions came up in response to my RFC.
The only real alternative I see for stable, is disabling MBIM support
on any dual NCM/MBIM function. Which of course will be a regression
for any user wanting MBIM, making it unacceptable.
drivers/net/usb/cdc_mbim.c | 11 +---------
drivers/net/usb/cdc_ncm.c | 49 ++++++++++++++++++++++++++++---------------
include/linux/usb/cdc_ncm.h | 1 +
3 files changed, 34 insertions(+), 27 deletions(-)
diff --git a/drivers/net/usb/cdc_mbim.c b/drivers/net/usb/cdc_mbim.c
index 248d2dc..16c8429 100644
--- a/drivers/net/usb/cdc_mbim.c
+++ b/drivers/net/usb/cdc_mbim.c
@@ -68,18 +68,9 @@ 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..4709fa3 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 setting on dual NCM/MBIM 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);
--
1.7.10.4
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