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    SubjectRe: [PATCH] ARM: OMAP: AM33XX: CAN: d_can: Add support for Bosch D_CAN controller
    On 04/03/2012 04:29 PM, AnilKumar, Chimata wrote:
    >>>> Please explain why this CAN controller cannot be handled by the existing
    >>>> C_CAN driver, eventually with some extensions. The register layout seems
    >>>> almost identical, at least.
    >>>>
    >>>> Wolfgang.
    >>>>
    >>>
    >>> These are the some of the pointers I can say, why I had gone for separate
    >>> file instead of existing driver:
    >>> * In case of D_CAN driver we can see all the registers are 32bit length
    >>> but in case of C_CAN registers are in 16bit length.
    >>
    >> How many bits in these 32 bit registers are used?
    >
    > In some cases (D_CAN_TXRQ, D_CAN_INTPND, D_CAN_MSGVAL) I have used all the
    > bits, in some cases used few bits.
    >
    > Roughly I can say that its (higher 16bits) % of usages is similar as compare
    > to 16bits
    >
    > While checking the status of TXRequest registers and INT pending register,
    > which is a hot code path, we have to put if checks for register access.

    The c_can already has a c_can_read_reg32() function. It's for example
    used in the rx_poll function. You can make it a function pointer (i.e.
    pric->read_reg32()) for easy abstraction.

    >>> * Some of the registers, bit masks are different, so we have to add
    >>> checks on every API for differentiating the kind of device
    >>
    >> Which registers are this? Can you give us an example?
    >
    > I am pointing out some of the resisters
    > * Single registers in case of D_CAN but multiple register in case of C_CAN
    > So masks will change MASK, ARB, INTPND
    > * D_CAN_IFCMD is the combination of COMM request and COMM mask registers

    Maybe you can use the read_reg32 function on both c_can and d_can.

    regards, Marc

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