• Mariano Alvira's avatar
    ft2232: add a mechanism to specify channel in layout structs · 4a64820f
    Mariano Alvira authored
    
    
    FT2232-family chips have two or more MPSSE modules.   FTDI documentation
    calls these channels.  JTAG adapter drivers thus need to be able to choose
    which channel to use.  (For example, one channel may connect to a board's
    microcontroller, while another connects to a CPLD.)
    
    Since each channel has its own USB interface, libftdi (somewhat confusingly)
    identifies channels using INTERFACE_* symbols.  Most boards use INTERFACE_A
    for JTAG, which is the default in OpenOCD.  But some wire up a different one.
    
    Note that there are two facets of what makes a wiring "layout":
    
     - The mapping between debug signals map and channel signals ... embedded
       in C functions.
    
     - Label used in Tcl configuration scripts ... part of the "layout" structure.
    
    By letting the channel be part of the layout struct, we permit sharing the C
    functions between Tcl-visible layouts, when those signal mappings are reused.
    Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
    4a64820f