On Wed, Aug 01, 2018 at 09:23:14PM +0100, Russell King - ARM Linux wrote:

On Wed, Aug 01, 2018 at 10:07:12PM +0200, Andrew Lunn wrote:

quoted

You might want to consider adding clk_optional_get() and
devm_clk_optional_get().

I think there's attempts to add such APIs but I don't think it's
trivial - it seems to require a _lot_ of discussion.

I think part of that is because of the quirky use of error codes.
If you look at clk_get(), it calls __of_clk_get_by_name() which
returns:

 -ENOENT if DT is disabled
 -ENOENT if the device has no DT node
 -EPROBE_DEFER if the lookup in DT succeeds but there's no registered
   clock
 -EINVAL if the device has a DT node but the lookup of the name
   failed (in otherwords, the optional clock was omitted)
 -ENOENT if the clocks = property has not enough clocks for the
    clock-names property
 -ENOMEM if we fail to allocate the clk
 -ENOENT if __clk_get() fails

That makes it hard. I added phy_optional_get() early on, when the
error cases were simple. Hopefully they remain simple...

      Andrew