On Fri, Nov 30, 2018 at 10:25:37AM +0000, Phil Edworthy wrote: > Hi Stephen, > > 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 superseded by clk_get_sys() returning -ENOENT.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. > > > +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. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up
