Issue #65 has a regression for ether devices.

[einarjon]

Renaming the class variable has a side-effect:
https://github.com/linux-usb-gadgets/libusbgx/blob/master/src/function/ether.c#L70

Now the library will want to write to the file "class_" instead of "class", and that breaks
usbg_create_function() if f_attrs != NULL.

One way to fix that:

diff --git a/src/function/ether.c b/src/function/ether.c
index a1d20f1..fd29312 100644
--- a/src/function/ether.c
+++ b/src/function/ether.c
@@ -23,9 +23,9 @@ struct usbg_f_net {
        struct usbg_function func;
 };
 
-#define NET_DEC_ATTR(_name)                                            \
+#define NET_DEC_ATTR2(_name,_filename)                                 \
        {                                                               \
-               .name = #_name,                                         \
+               .name = #_filename,                                     \
                .ro = false,                                            \
                .offset = offsetof(struct usbg_f_net_attrs, _name),     \
                .get = usbg_get_dec,                                    \
@@ -34,6 +34,8 @@ struct usbg_f_net {
                .export = usbg_set_config_node_int,                     \
        }
 
+#define NET_DEC_ATTR(_name) NET_DEC_ATTR2(_name, _name)
+
 #define NET_RO_STRING_ATTR(_name)                                      \
        {                                                               \
                .name = #_name,                                         \
@@ -67,7 +69,7 @@ static struct {
        [USBG_F_NET_HOST_ADDR] = NET_ETHER_ADDR_ATTR(host_addr),
        [USBG_F_NET_IFNAME] = NET_RO_STRING_ATTR(ifname),
        [USBG_F_NET_QMULT] = NET_DEC_ATTR(qmult),
-       [USBG_F_NET_CLASS] = NET_DEC_ATTR(class_),
+       [USBG_F_NET_CLASS] = NET_DEC_ATTR2(class_,class),
        [USBG_F_NET_SUBCLASS] = NET_DEC_ATTR(subclass),
        [USBG_F_NET_PROTOCOL] = NET_DEC_ATTR(protocol)
 };

Confirmed broken for NCM and RNDIS in master, but only if usbg_create_function() is called with f_attrs != NULL.
The error is in usbg_f_net_set_attrs(): Setting attr USBG_F_NET_CLASS returns USBG_ERROR_NO_ACCESS

[einarjon]

Relates to Issue #65

[einarjon]

This is actually worse than described:
The class/subclass/protocol parameters only exist for rndis, so trying to set those values breaks ncm/ecm devices

# ls /config/usb_gadget/g1/functions/rndis.usb0/
class  dev_addr  host_addr  ifname  os_desc  protocol  qmult  subclass
# ls /config/usb_gadget/g1/functions/ecm.usb0/
dev_addr  host_addr  ifname  qmult