Can you use the USB HID interface within a driver?

Can you use the USB HID interface within a driver?

[Adam Nielsen]

Hi all,

I'm about to start writing a driver for a Gigabyte Odin PC power supply. 
  This device has a USB connection which allows you to monitor 
temperature, voltages, current, etc.

Before I start coding the USB side of things, I'd just like some advice 
as to the best way of communicating with the device.

I would rather write the driver in kernel space (so that it "just works" 
and provides a hwmon interface without installing extra software), 
however the device already appears to the system as a USB HID device, 
and so gets claimed by the existing usbhid driver.

Is there any way to interface with the HID driver from within another 
driver?  Or will I have to claim the device first (or disconnect 
usbhid), and communicate with it myself?

I've tried to find some example code from a driver that already does 
this (such as a USB keyboard driver) but I'm having some trouble finding 
one!  The closest drivers I can find are all the ones in 
drivers/hid/usbhid, but they all seem to be "embedded" in hid-core.c. 
Does that mean I need to modify hid-core.c to call my driver?

Or perhaps someone could point me in the direction of a USB HID driver 
that does things "properly" already?

Many thanks,
Adam.

Re: Can you use the USB HID interface within a driver?

[Oliver Neukum]

Am Samstag, 1. November 2008 12:44:51 schrieb Adam Nielsen:
> I've tried to find some example code from a driver that already does 
> this (such as a USB keyboard driver) but I'm having some trouble finding 
> one!  The closest drivers I can find are all the ones in 
> drivers/hid/usbhid, but they all seem to be "embedded" in hid-core.c. 
> Does that mean I need to modify hid-core.c to call my driver?
> 
> Or perhaps someone could point me in the direction of a USB HID driver 
> that does things "properly" already?

Please post "lsusb -v" for your device.

	Regards
		Oliver

Re: Can you use the USB HID interface within a driver?

[Adam Nielsen]

>> Or perhaps someone could point me in the direction of a USB HID driver 
>> that does things "properly" already?
> 
> Please post "lsusb -v" for your device.

Here's the output.  I don't think any of the "class" drivers are 
suitable, except as templates for interfacing with the main HID code...I 
think...

Bus 008 Device 002: ID 1044:4001 Chu Yuen Enterprise Co., Ltd
Device Descriptor:
   bLength                18
   bDescriptorType         1
   bcdUSB               1.10
   bDeviceClass            0 (Defined at Interface level)
   bDeviceSubClass         0
   bDeviceProtocol         0
   bMaxPacketSize0         8
   idVendor           0x1044 Chu Yuen Enterprise Co., Ltd
   idProduct          0x4001
   bcdDevice            1.01
   iManufacturer           1 GIGABYTE TECHNOLOGY
   iProduct                2 GBT 800W PSU
   iSerial                 0
   bNumConfigurations      1
   Configuration Descriptor:
     bLength                 9
     bDescriptorType         2
     wTotalLength           34
     bNumInterfaces          1
     bConfigurationValue     1
     iConfiguration          0
     bmAttributes         0xa0
       (Bus Powered)
       Remote Wakeup
     MaxPower              100mA
     Interface Descriptor:
       bLength                 9
       bDescriptorType         4
       bInterfaceNumber        0
       bAlternateSetting       0
       bNumEndpoints           1
       bInterfaceClass         3 Human Interface Device
       bInterfaceSubClass      0 No Subclass
       bInterfaceProtocol      0 None
       iInterface              0
         HID Device Descriptor:
           bLength                 9
           bDescriptorType        33
           bcdHID               1.10
           bCountryCode            0 Not supported
           bNumDescriptors         1
           bDescriptorType        34 Report
           wDescriptorLength      32
          Report Descriptors:
            ** UNAVAILABLE **
       Endpoint Descriptor:
         bLength                 7
         bDescriptorType         5
         bEndpointAddress     0x81  EP 1 IN
         bmAttributes            3
           Transfer Type            Interrupt
           Synch Type               None
           Usage Type               Data
         wMaxPacketSize     0x0008  1x 8 bytes
         bInterval              10
Device Status:     0x0000
   (Bus Powered)


Cheers,
Adam.

Re: Can you use the USB HID interface within a driver?

[Kay Sievers]

On Sat, Nov 1, 2008 at 13:32, Adam Nielsen <a.nielsen@shikadi.net> wrote:
>>> Or perhaps someone could point me in the direction of a USB HID driver
>>> that does things "properly" already?
>>
>> Please post "lsusb -v" for your device.
>
> Here's the output.  I don't think any of the "class" drivers are suitable,
> except as templates for interfacing with the main HID code...I think...

I think, a real in-kernel driver for HID Power devices, which exports
the device as a "power_supply" device to userspace, would be nice.

That way, USB UPS's which support the HID Power devices:
  http://www.usb.org/developers/devclass_docs/pdcv10.pdf

would show up like any other battery and AC connector and userspace
could handle all of them without any specialized code:
  ls -1 /sys/class/power_supply/BAT0/
  alarm
  energy_full
  energy_full_design
  energy_now
  manufacturer
  model_name
  power
  present
  serial_number
  status
  technology
  type
  voltage_min_design
  voltage_now
  ...

Thanks,
Kay

Re: Can you use the USB HID interface within a driver?

[Jiri Kosina]

On Sat, 1 Nov 2008, Adam Nielsen wrote:

> I would rather write the driver in kernel space (so that it "just works" 
> and provides a hwmon interface without installing extra software), 
> however the device already appears to the system as a USB HID device, 
> and so gets claimed by the existing usbhid driver.

There is a long blacklist/ignorelist in the usbhid driver, for the VID/PID 
combinations that we don't want to have claimed by usbhid driver, because 
there is a more specific one.

> Is there any way to interface with the HID driver from within another 
> driver? Or will I have to claim the device first (or disconnect usbhid), 
> and communicate with it myself?
> I've tried to find some example code from a driver that already does this
> (such as a USB keyboard driver) but I'm having some trouble finding one!  The
> closest drivers I can find are all the ones in drivers/hid/usbhid, but they
> all seem to be "embedded" in hid-core.c. Does that mean I need to modify
> hid-core.c to call my driver?

For 2.6.28, the HID code has been completely refactored, and converted 
into a proper bus, making it possible to write driver easily in a way that 
the driver implements only parts where device deviates from the HID 
standard, and lets the rest to be handled by generic code. I guess this is 
what you are looking for?

Please look at drivers/hid in 2.6.28-rc1 or newer. There are quite a 
couple of drivers already using this new infrastructure.

If you have any further questions, I'll be happy to help you, but I will 
be completely offline until 11th November, sorry.

Hope this helps,

-- 
Jiri Kosina
SUSE Labs

Re: Can you use the USB HID interface within a driver?

[Adam Nielsen]

> For 2.6.28, the HID code has been completely refactored, and converted 
> into a proper bus, making it possible to write driver easily in a way that 
> the driver implements only parts where device deviates from the HID 
> standard, and lets the rest to be handled by generic code. I guess this is 
> what you are looking for?

Yes, that sounds like exactly what I'm after!  This device seems to be 
HID with a custom protocol over the top, so presumably I can let the HID 
driver handle all the USB initialisation and just focus on the protocol.

> Please look at drivers/hid in 2.6.28-rc1 or newer. There are quite a 
> couple of drivers already using this new infrastructure.

Great, I'll have a look now - thanks!

> If you have any further questions, I'll be happy to help you, but I will 
> be completely offline until 11th November, sorry.

Thanks for that!  I'll see how I go.  If there are existing drivers I 
can use as examples, hopefully I should be okay for the most part.

Cheers,
Adam.

Driver for new hid class (was: Can you use the USB HID interface within a driver?)

[Adam Nielsen]

>> For 2.6.28, the HID code has been completely refactored, and converted 
>> into a proper bus, making it possible to write driver easily in a way 
>> that the driver implements only parts where device deviates from the 
>> HID standard, and lets the rest to be handled by generic code. I guess 
>> this is what you are looking for?
> 
> Yes, that sounds like exactly what I'm after!  This device seems to be 
> HID with a custom protocol over the top, so presumably I can let the HID 
> driver handle all the USB initialisation and just focus on the protocol.

Okay, I've upgraded to 2.6.28-rc2 and started writing a driver for the 
new hid class.  It didn't take long for me to get stuck though :-(

When I load my module, it calls hid_register_driver() which returns 
0/success.  However that's as far as it gets.  I've defined a probe 
function to attach to the device, but this never gets called.

Is there something else I need to do?  The USB IDs are right, and I 
tried replugging the device with my "driver" loaded but it seems to be 
ignored.  It seems the device appears as a full HID input 
implementation, so it gets an evdev device associated with it.

Does this mean I need to blacklist it to stop the HID input driver from 
claiming it?  Or should my driver be able to claim it in preference to 
the input driver as mine is for a specific device, as opposed to the 
whole class?

Thanks,
Adam.

Re: Driver for new hid class

[Jiri Slaby]

On 11/02/2008 07:43 AM, Adam Nielsen wrote:
> Does this mean I need to blacklist it to stop the HID input driver from
> claiming it?

Yes, add the ids also to hid_blacklist to forbid generic driver binding the device.