Messages in this thread | | | From | Phil Edworthy <> | Subject | RE: [PATCH v3 1/2] clk: Add of_clk_get_by_name_optional() function | Date | Mon, 30 Jul 2018 16:38:48 +0000 |
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Hi Andy,
On 30 July 2018 17:04, Andy Shevchenko wrote: > On Mon, 2018-07-30 at 14:31 +0100, Phil Edworthy wrote: > > Quite a few drivers get an optional clock, e.g. a clock required to > > access peripheral's registers that is always enabled on some devices. > > > > This function behaves the same as of_clk_get_by_name() except that it > > will return NULL instead of -EINVAL. > > I'm puzzled a bit. > > __of_clk_get() may return few error codes, and to me ENOENT sounds > correct when clock is not found. Other error codes should be passed to the > caller even for optional clocks. > > If above is not true, we need to understand what circumstances for each > possible returned code are, and fix / act accordingly. > > P.S. Possible way like regulator framework does is to return -ENODEV. > > So, basically what I'm asking here is to be sure that single error code (for now > supposed -EINVAL) in this case is _the_ error code for absent / can't be > found clock. of_property_match_string() can return different return values for when: the "clock-names" property is missing (-EINVAL), the specified clock name in the "clock-names" property is missing (-ENODATA), or internal errors, (e.g. -EILSEQ). However, if you then call __of_clk_get() with the failed index, you just get the -EINVAL error.
Looking at it further, __of_clk_get() should return -ENOENT if passed a valid index (e.g. 0 when name=NULL) and the clock is not there. However, I think it will take a while to check all possible return values as it's not immediately clear what they are (to me).
I think the best thing is to test the return value of of_property_match_string() for -ENODATA, and deal with it then. Then deal with the case of name=NULL separately.
Thanks Phil
> - Fix check for clock not present. __of_clk_get() returns -EINVAL > > if it's not there. Cover case of when there is no clock name. > > -- > Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Intel Finland Oy
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