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SubjectRe: PROBLEM: full speed HID device with payload of 64 bytes

[ added linux-usb to CC ]

On Thu, 13 Aug 2009, Zeisel, Michael wrote:

> We experienced those problems with one of our devices, the Digital
> Pocket Memo 3 (DPM), by simply trying to receive button events via the
>
> Cat /dev/usb/hiddev0
>
> Command -> no success. The only difference between this device and older
> ones (which work on this kernel version) in the USB descriptor is the
> data payload which is 64 byte.
>
> To narrow down the cause for that behavior we simply took the same
> device, put in a FW with a low speed device protocol with a data payload
> of 8 byte and plugged it again to the PC.
>
> Now the button events produced some symbols in the "terminal", which
> proves that the device was recognized correctly and works.
>
> According to the USB 2.0 specification under
>
> http://www.usb.org/developers/docs/
>
> USB 2.0 specification, Chapter 5.7.4: Interrupt Transfer Bus Access Constraints
>
> A full speed device should support a maximum data payload of 64 bytes
> (Table 5-7. Full-speed Interrupt Transaction Limits: max.payload 64
> bytes x max.transfers 19 = max. 1216bytes/frame)
>
> To us it seems that the current implementation of the HID device support
> in LINUX just supports the protocol for low speed devices (Table 5-6.
> Low-speed Interrupt Transaction Limits: max.payload 8 bytes x
> max.transfers 6 = max. 48bytes/frame)
>
> On Windows OS and Mac OS all our devices work properly.

Could you please compile your kernel with CONFIG_USB_DEBUG and
CONFIG_HID_DEBUG enabled, modprobe the 'hid' module with 'debug=2'
parameter, and post the dmesg output that appears when you connect the
device and press the buttons?

> I think it is a good idea, if you would have a Digital Pocket Memo to
> experience the described behavior- so to whom I should send that device?

Let's see if something obvious pops out from the kernel debugging logs
first.

Thanks,

--
Jiri Kosina
SUSE Labs



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