[alsa-devel] [PATCH 1/8] clk: add helper function clk_is_match()

[Ben Dooks]

On Wed, Feb 25, 2015 at 09:27:57AM -0800, Mike Turquette wrote:
> Quoting Shawn Guo (2015-02-25 06:53:31)
> > Since commit 035a61c314eb ("clk: Make clk API return per-user struct clk
> > instances"), clk API users can no longer check if two struct clk
> > pointers are pointing to the same hardware clock, i.e. struct clk_hw, by
> > simply comparing two pointers.  That's because with the per-user clk
> > change, a brand new struct clk is created whenever clients try to look
> > up the clock by calling clk_get() or sister functions like clk_get_sys()
> > and of_clk_get().  This changes the original behavior where the struct
> > clk is only created for once when clock driver registers the clock to
> > CCF in the first place.  The net change here is before commit
> > 035a61c314eb the struct clk pointer is unique for given hardware
> > clock, while after the commit the pointers returned by clk lookup calls
> > become different for the same hardware clock.
> > 
> > A number of client drivers detecting if two struct clk pointers point to
> > the same one hardware clock by comparing the pointers are broken now.
> > As a stop-gap solution, this patch adds a helper function clk_is_match()
> > to test if two struct clk pointers point to the same hardware clock, so
> > that these client drivers can use to fix the regression.
> > 
> > Signed-off-by: Shawn Guo <shawn.guo at linaro.org>
> 
> Hi Shawn,
> 
> Thanks for the patch. I wrote a similar one last night but did not
> finish fixing up the drivers (and thus did not post it). I prefer my
> implementation below, and I'm happy to merge your driver fixes with it.
> 
> Regards,
> Mike
> 
> 
> 
> From: Michael Turquette <mturquette at linaro.org>
> Date: Wed, 25 Feb 2015 09:11:01 -0800
> Subject: [PATCH] clk: introduce clk_is_match
> 
> Some drivers compare struct clk pointers as a means of knowing
> if the two pointers reference the same clock hardware. This behavior is
> dubious (drivers must not dereference struct clk), but did not cause any
> regressions until the per-user struct clk patch was merged. Now the test
> for matching clk's will always fail with per-user struct clk's.
> 
> clk_is_match is introduced to fix the regression and prevent drivers
> from comparing the pointers manually.

small observaton, clk_is_same() is linguistically nicer.

-- 
Ben Dooks, ben at fluff.org, http://www.fluff.org/ben/

Large Hadron Colada: A large Pina Colada that makes the universe disappear.