Hi Wesley, On Mon, Mar 22, 2021 at 06:50:17PM -0700, Wesley Cheng wrote: > From: Chandana Kishori Chiluveru <cchiluve@xxxxxxxxxxxxxx> > > Hosts which request "OS descriptors" from gadgets do so during > the enumeration phase and before the configuration is set with > SET_CONFIGURATION. Composite driver supports OS descriptor > handling in composite_setup function. This requires to pass > signature field, vendor code, compatibleID and subCompatibleID > from user space. > > For USB compositions that contain functions which don't implement os > descriptors, Windows is sending vendor specific requests for os > descriptors and composite driver handling this request with invalid > data. With this invalid info host resetting the bus and never > selecting the configuration and leading enumeration issue. > > Fix this by bailing out from the OS descriptor setup request > handling if the functions does not have OS descriptors compatibleID. > > Signed-off-by: Chandana Kishori Chiluveru <cchiluve@xxxxxxxxxxxxxx> > Signed-off-by: Wesley Cheng <wcheng@xxxxxxxxxxxxxx> > --- > drivers/usb/gadget/composite.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c > index 72a9797..473edda6 100644 > --- a/drivers/usb/gadget/composite.c > +++ b/drivers/usb/gadget/composite.c > @@ -1945,6 +1945,12 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl) > buf[6] = w_index; > /* Number of ext compat interfaces */ > count = count_ext_compat(os_desc_cfg); > + /* > + * Bailout if device does not > + * have ext_compat interfaces. > + */ > + if (count == 0) > + break; > buf[8] = count; > count *= 24; /* 24 B/ext compat desc */ > count += 16; /* header */ Do we still need this fix? IIRC we had this change in our downstream kernel to fix the case when dynamically re-configuring ConfigFS, i.e. changing the composition of functions wherein none of the interfaces support OS Descriptors, so this causes count_ext_compat() to return 0 and results in the issue described in $SUBJECT. But I think this is more of a problem of an improperly configured ConfigFS gadget. If userspace instead removes the config from the gadget's os_desc subdirectory that should cause cdev->os_desc_config to be set to NULL and hence composite_setup() should never enter this handling at all, right? Jack -- The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
