linux-kernel - Re: USB HID plug and play, hardware developer frustration

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Message-ID: <20110129083638.GD26915@core.coreip.homeip.net>
Date:	Sat, 29 Jan 2011 00:36:38 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Robin Theunis <robint91@...il.com>
Cc:	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: USB HID plug and play, hardware developer frustration

Ho Robin,

On Sat, Jan 29, 2011 at 09:15:11AM +0100, Robin Theunis wrote:
> Hi Devs,
> 
> Currently I am design a USB product, and in that process I also look
> if almost every OS supports my device.
> The device is just only a HID digitizer or touch tablet thingy. It
> reports it self also as HID device. This is to have it
> work PLUG and PLAY. But I gotten a cold shower when trying this on my
> linux pcs. It doesn't work!
> I did some investigation and found that the linux (kernel) only
> support mouses and keyboard, all the other usage pages
> that are included in the USB HID specs aren't implemented.
> http://www.usb.org/developers/devclass_docs/Hut1_11.pdf
> 
> Is there a reason why they aren't implemented? especially the
> digitizer thingies because of all the new tablets?

Linux HID driver does have code to handle digitizers, please take a look
at drivers/hid/hid-input.c::hidinput_configure_usage().

> Is it difficult
> to make a driver to support my device?

It should not be. You might need to tweak usage mappings a bit by the
way of writing small HID sub-driver. Look for examples in
drivers/hid/hid-<vendor>.c

If you need additional help I'd recommend asking on
linux-input@...r.kernel.org

> I have seen that there are a
> lot of wacom drivers, I think doing all the same thing.
>

Wacoms are quite different since they are not HID devices but handler by
a completely separate driver.

Thanks.

-- 
Dmitry
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