On Wed, Jan 4, 2012 at 6:32 AM, Rob Herring <robherring2@xxxxxxxxx> wrote: > 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@xxxxxxxxxxxxx> 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. Agreed. > 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 point of this? The original clk_hw was defined simply as: struct clk_hw { struct clk *clk; }; It's only purpose in life was as a handle for navigation between the opaque struct clk and the hardware-specific struct my_clk_hw. struct clk_hw is defined in clk.h and everyone can see it. If we're suddenly OK putting clk data in this structure then why bother with an opaque struct clk at all? > 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. To answer your question on what data we're trying to expose: platform code commonly needs the parent pointer and the clk rate (and by extension, the rate of the parent). For debug/error prints it is also nice to have the clk name. Generic clk flags are also conceivably something that platform code might want. I'd like to spin the question around: if we're OK exposing some stuff (in your example above, the parent pointer), then what clk data are you trying to hide? Regards, Mike > > Rob -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html