On Tuesday 04 September 2012 11:13:52 Bjørn Mork wrote: Hi, > there is some work going on trying to support CDC MBIM devices in > Linux ( http://www.usb.org/developers/devclass_docs/MBIM10.zip ) Yet another protocol. > The protocol is based on CDC NCM with a rather complex control protocol > ecapsulated in CDC using SendEncapsulatedCommand and > GetEncapsulatedResponse, similar to how QMI/wwan devices combine CDC ECM > with the Qualcomm QMI control protocol. > > Based on these similarities, I proposed to reuse as much as possible of I am afraid cdc_ncm is not very clean at present. The bundling of network packets into larger units should be done so that usbnet is aware of what is happening. In particular starting a timer inside a subdriver is very dirty. > the cdc-ncm and cdc-wdm drivers, creating a construct similar to that > provided by qmi_wwan: Exporting the control protocol as a /dev/cdc-wdmX > character device to some userspace application doing all the complex > policy decisions. Greg Suarez has started out on this track, but has Is code available to be seen? > found that the cdc-wdm subdriver interface must be extended somewhat for > this to be possible. At the very least, the main driver need to handle > some notifications which are ignored by cdc-wdm. And depending on which Which ones? > CDC MBIM features we are going to support, there is also a possibility > that the main driver will have to intercept messages between the > userspace and the cdc-wdm subdriver. Ouch. > The following patch is meant as a RFC for a basic interface change, > adding the flexibility the new driver will need. I would very much > welcome comments on > - the whole concept of doing the same for MBIM as for QMI Sensible. > - whether data interception may be acceptable at all in one direction yes, the other is very problematic > - the proposed symbol change, including restricting it to GPL > drivers The changes are mainly sensible. Simply changing the license is not nice. It seems to me, once something has been allowed, it should stay allowed. > - anything else that pops up in your head while reading this :-) > > The RFC patch also includes the oneline change for qmi_wwan to use the > new API. If this approach is acceptable, I would like to push these > changes through net-next to reduce the cross-tree dependencies. This is the brute force approach: @@ -224,6 +224,11 @@ static void wdm_int_callback(struct urb *urb) goto exit; } + /* check for callback function */ + if (desc->driver_info->status && + desc->driver_info->status(desc->intf, urb)) + goto exit; + And it breaks the status model. This particular approach is not good. Even with MBIM you want the driver to retrieve the responses. So the correct approach would be to intercept the responses to GET_ENCAPSULATED_RESPONSE and filter them, more or less like a line discipline. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
