[BRLTTY] bc640: Some debug info
Mario Lang
mlang at delysid.org
Thu Feb 7 05:12:05 EST 2008
Dave Mielke <dave at mielke.cc> writes:
>>Yes, for now, thats all that is necessary. The Linux hiddev
>>interface has a bunch of ioctls as well (all defined in linux/hiddev.h).
>>They can be used to get "reports" and do other things, but
>>reading incoming events is as simple as reading from the device.
>
> Do you know what writing to a hiddev is suposed to do?
No. I wasn't brave enough to try this yet, since the last
display I had for driver hacking (the Trio) died when I
wrote a slightly malformed packet to it...
> Can you, for example, just write a regular byte stream to it? If so,
> then I can tell you how to do a regular Alva write and we can see if
> that works.
If you tell me which stream, I can try. I havent groked the
hiddev interface yet though...
> Is /dev/usb/hiddev0 a device in its own right or is it a symlink to somewhere
> else?
Its a special device file. Quoting Documentation/usb/hiddev.txt
from the linux kernel tree:
"The hiddev interface is a char interface using the normal USB major,
with the minor numbers starting at 96 and finishing at 111."
udev automatically creates these device file if a HID compatible
USB device gets connected.
> If the device is found via searching usbfs, do you know how to then translate
> that to the right hiddev device to open or can the usbfs device be opened and
> read?
hiddev and plain usb devices are on a different layer in the kernel.
If we were to use usb devices directly, we would need to
impelemtn HID ourselves... There is a libhid which can be
used to do HID IO from userspace, but I tried it yesterday
but it is buggy. It managed to find the correct device via vendor/product
ID, but when trying to retrieve the HID descriptor it fails. This bug
seems to be common, since I found some postings about it on the net.
So for now, I think we are better of using the linux hiddev interface.
>>Key group 1: The thumb keys. The device has 5 thumb keys, numbers 0 to 4 from
>>left to right.
>
> All the same size and equally spaced?
Not quite, but mostly. I have the device at home, can
examine this in detail today evening.
>>Key group 3: These keys are located below the display line, on
>>top of the device. There are 8 of those keys, in the middle
>>you have "cursor keys" with up/down, left/right, and one button
>>in the middle. On the sides, you have two additional keys.
>>Below are the keycodes drawn in the same layout:
>
> Are these keys below the routing keys or above them?
Below.
> Do there seem to be any limitations regarding which keys can be pressed
> together?
I havent tried any key combinations yet.
--
CYa,
⡍⠁⠗⠊⠕ | Debian Developer <URL:http://debian.org/>
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