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    SubjectRe: [PATCH] sh: maple: add support for Maple controller as a joystick
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    On Sat, 2008-12-20 at 12:19 -0800, Dmitry Torokhov wrote:
    > On Saturday 20 December 2008 08:07:27 Adrian McMenamin wrote:
    > > On Sat, 2008-12-20 at 15:16 +0000, Matt Fleming wrote:
    > > > On Fri, Dec 19, 2008 at 11:15:42PM +0000, Adrian McMenamin wrote:
    > > > > Add support for the SEGA Dreamcast Maple controller as a joystick
    > > >
    > > > [snip]
    > > >
    > > > > + struct dc_pad *pad = maple_get_drvdata(mapledev);
    > > > > + struct input_dev *dev = pad->dev;
    > > > > + unsigned char *res = mq->recvbuf;
    > > > > +
    > > > > + buttons = ~cpu_to_le16(*(unsigned short *)(res + 8));
    > > > > +
    > > >
    > > > I may be wrong but shouldn't this use the I/O accessor functions?
    > >
    > > It's not iomemory, so I don't think so. The maple bus writes to a buffer
    > > in the physical RAM.
    > >
    >
    > Hmm, but why we are going _from_ cpu order to le16??? I'd expect we
    > wanted to do conversion the other way around. I pulled it out of 'next'
    > for now.
    >
    The data is transmitted here by the bus in 32 bit little endian blocks
    but makes sense in le16 bit lumps. Off is 1 and on is 0 - hence the ~

    The first 16 bits are the button data the next 16 bits are the (start
    of) the axis data. Both cpu and bus data (in this case - it can vary)
    are little endian.






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