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    SubjectRe: [spi-devel-general] Re: question on spi_bitbang
    On Friday 31 March 2006 11:07 am, Kumar Gala wrote:
    > My controller is just a shift register that I can set the  
    > characteristics of (bit length for example, reverse data).

    I've got a patch somewhere to enable LSB-first transfers in the API,
    though without an implementation, if you're interested. I'll post it
    as an RFC at some point.

    > > The chipselect() call should only affect the chipselect signal and,
    > > when you're activating a chip, its initial clock polarity. Though
    > > if you're not using the latest from the MM tree, that's also your
    > > hook for ensuring that the SPI mode is set up right.
    > Why deal with just clock polarity and not clock phase as well in
    > chipselect()?

    You could, but the point is that you _must_ set the initial polarity
    before setting the chipselect. Most SPI devices support modes 0 and 3,
    and make the choice based on the clock polarity when chipselect goes
    active. Changing polarity later would start a transfer. :)

    > It sounds like with the new patch, I'll end up setting txrx_word[] to
    > the same function for all modes.

    Yes, it does sound like that. If that works for you, I'd like to see
    that go into 2.6.17 kernels.

    - Dave
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