>> = Adam Richter
> = Oliver Neukum
>> I am currently interested in the USB user level drivers because
>> I think it may be better to move all Human Input Device USB drivers
>> to user land. The HID "report" descriptors are fairly complex, so
>No !
>At least keyboard has to remain in kernel, else no sysreq nor sak nor
>scrollback during boot.
That is already the situation when usbcore, the root hub driver
or the usb keyboard driver are loadable modules. However, I appreciate
your point and agree that it would assist debugging to retain the ability
to compile these things in.
>In addition it adds a lot of brittleness to require a
>demon running in single user mode, etc.
You have to be careful, but this is less "brittleness"
than, say, shared libraries. If the system still boots, its the
sort of thing you can "ssh in" to fix. If not, then you want to
have a ramdisk laying around with the daemon, which, unlike the
kernel modules would not need to be rebuilt for each version of
the kernel.
>> Since HID devices are pretty low bandwidth, I do not think there
>> is a performance reason for including them in the kernel, although I
>Accurate timestamps ?
Now that you mention it, if any software would really use that
feature, that would be a useful thing to add to the general usbdevfs
ioctl interface.
>> would be more reassured in this feeling if I had some numbers on what kind
>> of latency is needed for joysticks and the like in things like fast video
>> games.
>Please think of things like forcefeedback.
A force feedback joystick will likely involve round trips from
user land either way, unless you are proposing to embed something like
a terrain map in the kernel.
What I am most interested in is _numbers_ rather than what one
might call "performance FUD." Any statistics on required latencies,
etc., would be very helpful.
Anyhow, thanks for the insightful input.
Adam J. Richter __ ______________ 4880 Stevens Creek Blvd, Suite 104
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