[plt-scheme] FFI Question: C-Structures with byte blocks.

Question on using the FFI.

Have made some minimal headway in binding to libusb.

Given the following C structure, what should my define-cstruct look
like?  For now, assume the goal is to extract the null terminated
directory name from dirname and to follow the usb_bus *next linked list
chain. i.e. the other structure values can be ignored.

Its how to declare the "block" of char for dirname I'm unsure about.

Given:

struct usb_bus {
  struct usb_bus *next, *prev;

  char dirname[PATH_MAX + 1];

  struct usb_device *devices;
  u_int32_t location;

  struct usb_device *root_dev;
};

How do get the structure layout to work when dirname is a block of 4097 bytes. (PATH_MAX = 4096 in limits.h)

 (define-cstruct _buss_struct
    ((next _pointer)
     (previous _pointer)
     (dirname (_bytes o 4097))  ;; not what I really want to do here ??
     (devices _pointer)
     (location _int)
     (root_dev _pointer)))


Thanks