Add horizontal scroll support to ums driver

[Dmitry Marakasov]

Hi!

I've just bought Logitech USB-PS/2 Optical Mouse. In additional to usual
wheel, it has horizontal scroll support by moving wheel left/right, and
I would like that feature to work on my system. I've looked at ums
driver source and seems like it doesn't support horizontal scroll at
all. I think I can add support for it myself, but I could need some
documentation and maybe some help from USB gurus.

For now it's more or less clear to me what should be done in order to
support H scroll, but I lack understanding of how output packets are
formed in ums_add_to_queue(), i.e. those that come from /dev/ums0.

-- 
Best regards,
  Dmitry Marakasov               mailto:amdmi3 at amdmi3.ru