From: David MacCormack
Subject: [SDL] Linux joystick patch

I recently got myself a PS2 -> USB converter (a super joybox 5).  It
accepts 4 PSX/PS2 controllers.  It's implemented as a HID, which is nice
because it doesn't require its own driver, but the problem is that it's
implemented as a *single* HID -- that is, it shows up as a single
joystick with 19 axes, 4 hats, and 48 buttons.  This poses a problem for a
number of apps which use SDL (stella, fce ultra, zsnes, to name a few) and
see only a single (physical) joystick even though there are really 4
(logical) joysticks.  There are a number of these types of devices on the
market, and I've seen others post messages (in the zsnes forum, for
example) with the same problem, so I came up with what I think is a pretty
generic solution.

I patched src/joystick/linux/SDL_sysjoystic.c to include support for
logical joysticks; basically, it's a static array and supporting functions
that map a single physical joystick to multiple logical joysticks.  The
attached patch has the new code.  It's wrapped inside #ifndef
statements so that you can get the old behavior if you want.