Messages in this thread | | | From | Stephen Boyd <> | Subject | Re: [PATCH v8] clk: Add (devm_)clk_get_optional() functions | Date | Fri, 30 Nov 2018 10:55:48 -0800 |
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Quoting Russell King - ARM Linux (2018-11-30 03:04:46) > On Fri, Nov 30, 2018 at 10:25:37AM +0000, Phil Edworthy wrote: > > On 30 November 2018 09:09 Stephen Boyd wrote: > > > Quoting Phil Edworthy (2018-11-20 06:14:45) > > > > This adds clk_get_optional() and devm_clk_get_optional() functions to > > > > get optional clocks. > > > > They behave the same as (devm_)clk_get except where there is no clock > > > > producer. In this case, instead of returning -ENOENT, the function > > > > returns NULL. This makes error checking simpler and allows > > > > clk_prepare_enable, etc to be called on the returned reference without > > > > additional checks. > > > > > > Ok. I guess that works by virtue of how -ENOENT is returned by various > > > functions that are called deeper in the clk_get() path? I'm cautiously > > > optimistic. So cautious, we should probably add a comment to these optional > > > functions that indicate they rely on the functions they call to return -ENOENT > > > under the various conditions that make a clk optional. > > Yes, it does indeed rely on how clk_get() is implemented. > > Specifically, that if __of_clk_get_by_name() returns -EINVAL, the error is > > superseded by clk_get_sys() returning -ENOENT. > > As you say, a comment may help here. > > Each time the question of the optional clk_get() stuff comes up, we go > around the same discussions time and time again. So far, each time > has ended up flopping. > > Yes, clk_get() can only ever return -ENOENT if it falls back to the > non-DT methods, because it assumes that the clk tables are complete > (it can do nothing else.) > > I don't think it needs a comment because it's obvious from the code > and also from the implementation point of view.
Ok. I would still suggest a comment on of_clk_get_by_name() that indicates what types of return values happen in there. Otherwise it's obvious from the code after reading 3 or 4 functions deep (__of_clk_get_by_name -> __of_clk_get -> of_parse_phandle_with_args and __of_clk_get_from_provider) that this is what happens.
> > > > > +static inline struct clk *clk_get_optional(struct device *dev, const > > > > +char *id) > > > > > > Any kernel doc for this function? > > I took my cue from the surrounding functions, let me know if I have to add it. > > I don't see you need to - this is an internal function by way of the > "static inline" you have before it. It's not an API function.
It's static inline in a header file. That is an API function as far as I can tell.
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