On Thu, May 02, 2013 at 03:54:45PM -0400, Todd Showalter wrote:

On Thu, May 2, 2013 at 2:29 PM, Dmitry Torokhov
[off-list ref] wrote:

quoted

quoted

- any mapping library is going to have to be a mirror of the kernel
code, which means it's basically just a lot of duplicated effort with
the added penalty of update lag

The library can do much more than that. You also need to calibrate the
device (per user), adjust it to user's tastes and so on. Maybe you have
a user that is left-handed and you'd like to remap some keys? It is
certainly not kernel's job.

    I think calibration, dead-zones, easing, button remapping and the
like are a totally orthogonal problem.  They are nice to have, but
that's the kind of thing that belongs in a desktop environment's
accessibility settings, not at the input protocol level.

quoted

There also should not be lag if new devices follow the agreed upon
mapping.

    If we can have that, at least, it means the problem is eventually
fixed.  Maybe not for years, but at least someday.

quoted

The same thing can be done in a library. Libraries are easier then
kernels, you do not need to consume memory until needed and you do not
need to do the conversion if it is not needed. And it should be possible
to update the library whereas with kernel you mist likely need to reboot
the box.

Why do people believe that patching the kernel is easier than updating
userspace?

    The kernel is the core of the system; Linux isn't Linux without
the Linux kernel.  If I make a game input library and try to get
people to use it, there's a whole chicken-and-egg problem of getting
developers to support something nobody has installed, and getting
users to install something no developers support.  I have to convince
the distros to pick it up, and to keep updating it.  I have to monitor
changes in the kernel codebase to see if the library needs updating.
I have to deal with the possibility that the library becomes a useful
bandaid, with people saying "meh, this is a hard problem, punt the fix
to the library".  I have to hope that telling players to install
another dependency isn't going to lose me customers.

Until you get a traction with the new you might need to distribute it
with your game. Another option would be to extend already established
library, such as SDL, with the required functionality.

    The kernel has authority that a library does not, and it has a
distribution mechanism that a library does not.  The kernel is
effectively the source of the data; all I can do outside of that is
provide a filter and hope people use it.

No, I do not think so. Kernel provides a level of abstraction, but so
does X, ALSA, given desktop environment and so forth. If a task does not
require hardware access (and translating input events form one type to
another does not) one should think really hard whether it should be
done in kernel.

Thanks.

-- 
Dmitry