Attempting to write a device driver for the macbook's USB trackpad

[Rohit Grover]

I have contacted Rui Paulo already. He isn't working on a trackpad driver
for macbooks. :(

On Sat, Dec 27, 2008 at 1:41 PM, Vincent Hoffman <vince at unsane.co.uk> wrote:

> Rohit Grover wrote:
> > Hello People,
> >
> > I'm attempting to write a FreeBSD device driver for the USB trackpad on
> my
> > macbook.
> >
> Not much help but http://wiki.freebsd.org/AppleMacbook says or implies
> that Rui Paulo was working on somthing similar under the touchpad
> section, it might be worth talking to him directly
> (http://wiki.freebsd.org/RuiPaulo .)
> > The trackpad is an HID class device. Parsing the HID report descriptor
> > (fetched from an invocation of usbd_read_report_desc()) for this device
> > results in the following information:
> >
> > Legend: <descriptor_kind>: <page> <usage> <reportID>
> >       <hid_location>
> >
> > input: page: 0x9; usage: 0x1; reportID: 2
> >         size: 1, count: 1, loc: 0
> > input: page: 0x9; usage: 0x2; reportID: 2
> >         size: 1, count: 1, loc: 1
> > input: page: 0x9; usage: 0x3; reportID: 2
> >         size: 1, count: 1, loc: 2
> > input: page: 0x0; usage: 0x0; reportID: 2
> >         size: 5, count: 1, loc: 3
> > input: page: 0x1; usage: 0x30; reportID: 2
> >         size: 8, count: 1, loc: 8
> > input: page: 0x1; usage: 0x31; reportID: 2
> >         size: 8, count: 1, loc: 16
> > input: page: 0xffff; usage: 0x2; reportID: 5
> >         size: 8, count: 63, loc: 24
> > collection: page: 0x1; usage: 0x2; collection: 1; collevel: 1, reportID:
> 0
> >         size: 0, count: 0, loc: 0
> > collection: page: 0x1; usage: 0x1; collection: 0; collevel: 2, reportID:
> 0
> >         size: 0, count: 0, loc: 0
> > collection: page: 0xffff; usage: 0x1; collection: 0; collevel: 1,
> reportID:
> > 2
> >         size: 8, count: 2, loc: 0
> > feature: page: 0xffff; usage: 0x4, reportID: 5
> >         size: 8, count: 1, loc: 0
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 8
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 16
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 24
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 32
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 40
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 48
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 56
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 64
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 72
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 80
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 88
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 96
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 104
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 112
> > feature: page: 0x0; usage: 0x0, reportID: 5
> >         size: 8, count: 1, loc: 120
> > end_collection: page: 0x1; usage: 0x31, reportID: 2
> >         size: 8, count: 2, loc: 0
> > end_collection: page: 0x0; usage: 0x0, reportID: 2
> >         size: 8, count: 2, loc: 0
> > end_collection: page: 0xffff; usage: 0x4, reportID: 5
> >         size: 8, count: 16, loc: 0
> >
> > As can be seen, there are two distinct report IDs being used. Report ID 2
> > describes the mouse-buttons and XY deltas; and since the generic UMS
> driver
> > in Freebsd is able to parse these values, the macbook's trackpad is
> usable.
> > I would like to enhance the ums driver to report information from the
> > pressure sensors--with the hope that this will allow the detection of tap
> > events.
> > I suspect that the reports with ID == 5 will contain this information. Of
> > particular interest to me is the following (from the previous table):
> >
> > input: page: 0xffff; usage: 0x2; reportID: 5
> >         size: 8, count: 63, loc: 24
> >
> > Unfortunately, this report uses a vendor specific page (0xffff), and
> > therefore will require some reverse engineering before it can be
> deciphered.
> >
> > I need help with receiving HID reports for both ID == 2 and ID == 5.
> > Currently, the interrupt handler (ums_intr) only parses reports with
> ID==2.
> > Based on my reading of the code, ums_attach() needs to setup sc->sc_iid
> and
> > sc->sc_isize based on the report-descriptors fetched from the device; but
> in
> > the case where there are multiple reportIDs supported by the device, the
> > current setup code uses values from only the first reportID.
> >
> > In order to parse reportID 2, sc->sc_isize is set to a value of 4 bytes:
> 1
> > byte for the reportID header, together with 3 bytes for the
> button/XY-delta
> > values.
> > To accommodate an additional 63 bytes for the input in reportID 5, I am
> > guessing that I should set sc->sc_isize to 68:  for the 63 bytes starting
> at
> > bit offset 24; with allowance for one additional byte which may be
> necessary
> > to accommodate a reportID header. I still don't know how to initialize
> > sc->sc_iid to handle both report IDs.
> >
> > Can someone please help me with setting up the device to receive reports
> > with both IDs so that I can begin reverse-engineering the vendor-specific
> > content of reportID 5?
> >
> > regards,
> > Rohit.
> > _______________________________________________
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>
>