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    SubjectRe: [spi-devel-general] adding bits_per_word to struct spi_board_info to mirror struct spi_device
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    On Mon, 2007-05-07 at 19:47 -0400, Mike Frysinger wrote:
    > On 4/25/07, David Brownell <david-b@pacbell.net> wrote:
    > > On Wednesday 25 April 2007, Mike Frysinger wrote:
    > > > the spi_device structure has a bits_per_word so that you can change
    > > > the value on a per-device setting, yet the spi_board_info structure
    > > > does not ... this means that the bus-specific structure has to have a
    > > > bits_per_word member which the spi bus driver will copy into the spi
    > > > device bits_per_word member
    > >
    > > Actually that's more likely a driver-specific characteristic than
    > > something related to board wiring/configuration ... a characteristic
    > > of the particular protocol requests being made. That's why for
    > > example bits_per_word has a per-transfer override, and drivers are
    > > able to call spi_setup(spi).
    >
    > hmm, true ...
    >
    > > > is there something obvious i'm missing ? seems to me that if the
    > > > generic spi framework respects bits_per_word on a per-spi device
    > > > basis, then it should be exposed in the generic info structure so that
    > > > the setting can be tracked in the boards file ...
    > >
    > > The initial driver set didn't need it, that's all. ISTR someone
    > > else pointed out this quirk, but never provided a patch to resolve
    > > the issue.
    >
    > so which direction should it be ? or should it be both ? :)
    >
    > Blackfin at the moment is doing DMA/bits_per_word setup in the boards
    > ... we could move these to the drivers and have each one just call
    > spi_setup() at init, or i could post a patch for the common framework
    > if you think that's an OK direction to [also] go ...
    > -mike

    Yes, it is very common for spi_framework. DMA setting as well as
    bits_per_word setup should be imported to spi_board_info struct. And
    currently, there are some duplicated data members in spi_device struct
    spi_board_info struct. This two structs are confused driver writers and
    boards driver users.

    Thanks
    -Bryan Wu
    -
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