The problem is that call to libusb_get_descriptor() is defined as taking a void* for the buf parameter: 

int libusb_get_descriptor(
  void *dev, unsigned char type, unsigned char index, void *buf, int s
+ize
)

[download]

But the typemap for that is void *            T_PTR, and that translates as

T_PTR     $var = INT2PTR($type,SvIV($arg)).

Ie. it is expecting the pointer to be passed as an integer in the IV slot. Hence the "argument isn't numeric".

In order to pass a buffer in the PV slot, as the perl code is doing, the type should be one of those that translates to

T_PV    $var = ($type)SvPV_nolen($arg).

Eg. char *            T_PV

There seem to be several of the functions that make this error.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"I'd rather go naked than blow up my ass"

In reply to Re: Problem trying to use Device::USB by BrowserUk
in thread Problem trying to use Device::USB by scliffe

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