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    SubjectRe: [PATCH v4 3/6] clk: introduce the common clock framework
    On 01/03/2012 08:15 PM, Richard Zhao wrote:
    > On Fri, Dec 16, 2011 at 04:45:48PM -0800, Turquette, Mike wrote:
    >> On Wed, Dec 14, 2011 at 5:18 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
    >>> On Tue, 13 Dec 2011, Mike Turquette wrote:

    snip

    >>>> +/**
    >>>> + * clk_init - initialize the data structures in a struct clk
    >>>> + * @dev: device initializing this clk, placeholder for now
    >>>> + * @clk: clk being initialized
    >>>> + *
    >>>> + * Initializes the lists in struct clk, queries the hardware for the
    >>>> + * parent and rate and sets them both. Adds the clk to the sysfs tree
    >>>> + * topology.
    >>>> + *
    >>>> + * Caller must populate clk->name and clk->flags before calling
    >>>
    >>> I'm not too happy about this construct. That leaves struct clk and its
    >>> members exposed to the world instead of making it a real opaque
    >>> cookie. I know from my own painful experience, that this will lead to
    >>> random fiddling in that data structure in drivers and arch code just
    >>> because the core code has a shortcoming.
    >>>
    >>> Why can't we make struct clk a real cookie and confine the data
    >>> structure to the core code ?
    >>>
    >>> That would change the init call to something like:
    >>>
    >>> struct clk *clk_init(struct device *dev, const struct clk_hw *hw,
    >>> struct clk *parent)
    >>>
    >>> And have:
    >>> struct clk_hw {
    >>> struct clk_hw_ops *ops;
    >>> const char *name;
    >>> unsigned long flags;
    >>> };
    >>>
    >>> Implementers can do:
    >>> struct my_clk_hw {
    >>> struct clk_hw hw;
    >>> mydata;
    >>> };
    >>>
    >>> And then change the clk ops callbacks to take struct clk_hw * as an
    >>> argument.
    > We have to define static clocks before we adopt DT binding.
    > If clk is opaque and allocate memory in clk core, it'll make hard
    > to define static clocks. And register/init will pass a long parameter
    > list.

    DT is not a prerequisite for having dynamically created clocks. You can
    make clock init dynamic without DT.

    What data goes in struct clk vs. struct clk_hw could change over time.
    So perhaps we can start with some data in clk_hw and plan to move it to
    struct clk later. Even if almost everything ends up in clk_hw initially,
    at least the structure is in place to have common, core-only data
    separate from platform data.

    What is the actual data you need to be static and accessible to the
    platform code? A ptr to parent clk is the main thing I've seen for
    static initialization. So make the parent ptr be struct clk_hw* and
    allow the platforms to access.

    Rob


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