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    SubjectRe: [PATCH 4/8] dmaengine: ste_dma40: Do not configure channels during an channel allocation
    2013/4/12 Lee Jones <lee.jones@linaro.org>:
    > So I need to devise another way, as this function cannot be called
    > here either. Using the dmaengine API, allocating a channel and
    > configuring it are to be completed using different calls. Using the
    > API correctly, there is no way the driver can setup the channel
    > with all of the relevant information during allocation time.
    >
    > The steps are as follows:
    >
    > dma_request_channel() - here we only allot a channel number and
    > allocate the appropriate resources for the
    > channel.
    >
    > dma_slave_config() - this is where we're meant to configure the
    > channel, so d40_config_write() needs to be
    > called here, as only dma_slave_config() will
    > carry the information required so as
    > d40_*_cfg() can make the correct decisions.

    The choice between whether a physical or a logical channel is used is
    not something that is configurable via dma_slave_config(). And
    d40_config_write() only needs that information, and that information is
    available in dma_request_channel(). Therefore no more information
    relevant to d40_config_write() will be obtained in dma_slave_config().
    Hence d40_config_write() can be called in dma_request_channel().


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