[OLPC-devel] USB device support

[David Zeuthen]

On Thu, 2006-08-24 at 12:52 -0700, Mitch Bradley wrote:
> Does anybody know of any efforts to support USB devices from userland?

libusb, been around for many years.

> Having to upgrade kernels just to support a random device seems like the 
> wrong answer for an easy-to-use machine.

No, the driver just need to go into the upstream kernel and you will get
support for it. We need to be able to push out new kernel updates for
security fixes _anyway_, so it needs to be at least as easy to update
the OS kernel that a piece of OS user land software. The kernel is by
far the component that needs the most security update, mozilla etc.
being another big contender.

Btw, I will argue that user space drivers in many ways create more
problems for user land than kernel space drivers. For example, you need
the driver to come with user land udev rules that specifically changes
the permissions in /proc/usb/* (or /dev/usb* nowadays) based on VPD such
as USB vendor and product id's. Now, if the driver just implemented a
standard kernel functional interface like e.g. video4linux or whatever
the standard rules for changing ownership on those would suffice.
Problem is that few userland drivers care to do this in a distro
invariant way. So we have the usual problem that we have everywhere else
in Linux-based OS'es - that the user will have to resort to a terminal
emulator to install the driver.

So, I don't really buy that user space drivers are easier than kernel
space drivers. It's more of a myth.

Of course, user space drivers are nice if you care proprietary software
(since there is no kernel ABI that breaks all the time) and stability
(since it only kills the user space program using it) but I guess this
is not what you were getting at. And both niceties are totally void IMO
for OLPC anyway: we should not care about proprietary closed drivers in
OLPC; and we shouldn't include drivers that crash be they either user or
kernel land. That's what I personally think, anyway.

    David