Re: Byte swapping u16 data in HID report

On Wed, 1 Jun 2011 01:32:15 -0400
simon@mungewell.org wrote:

Hi,
I'm looking into fixing the Sixaxis controller (hid-sony.c) so that the
accelerometers and gyro data are reported via a joystick axis.

I have patched the HID descriptor so that the values are seen, however
they are reported high byte first (0x2FF -> 0x02, 0xFF) which appears to
be contrary to the HID spec.
--
5.8 Format of Multibyte Numeric Values
Multibyte numeric values in reports are represented in little-endian
format, with the least significant byte at the lowest address.
--

I'm working on the assumption that the data can be 'fixed' before it is
parsed. Would intercepting 'hid_get_report()' be a good place and how can
I locate the actual data bytes to do a 'bswap16()'.

I'm thinking something like:
--
	if (sc->quirks & SIXAXIS_CONTROLLER_USB) {
		hdev->hid_get_report = sixaxis_hid_get_report;
	}
--

Any suggestions/comments?
Simon.

Marcin Tolysz (added to CC), worked on the sixaxis descriptor before,
see http://permalink.gmane.org/gmane.linux.bluez.kernel/5184

Look in particular at the sony_raw_event() function.

I also like his approach of overriding HID descriptors with the
firmware framework in principle, even if its practical use still needs
some evaluation.

Regards,
   Antonio

-- 
Antonio Ospite
http://ao2.it

PGP public key ID: 0x4553B001

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