Messages in this thread | | | Subject | Re: [PATCH] clk: <linux/clk.h>: correct clk_get_parent() documentation | From | Randy Dunlap <> | Date | Tue, 27 Apr 2021 11:10:42 -0700 |
| |
On 4/27/21 11:03 AM, Russell King - ARM Linux admin wrote: > On Tue, Apr 27, 2021 at 10:07:04AM -0700, Randy Dunlap wrote: >> On 4/27/21 2:38 AM, Russell King - ARM Linux admin wrote: >>> On Mon, Apr 26, 2021 at 08:13:42PM -0700, Randy Dunlap wrote: >>>> Make the kernel-doc return value agree with both the stub implementation >>>> in <linux/clk.h> and the non-stub function in drivers/clk/clk.c. >>>> >>>> Signed-off-by: Randy Dunlap <rdunlap@infradead.org> >>>> Cc: Russell King <linux@armlinux.org.uk> >>>> Cc: linux-clk@vger.kernel.org >>>> --- >>>> There are several drivers that call clk_get_parent() and use its >>>> return value as though it returns an ERR_PTR(). I am working on a >>>> patch series to fix those. >>> >>> The whole premise of the CLK API is that: >>> >>> - clk values that IS_ERR() returns true are errors >>> - clk values that IS_ERR() returns false are valid >>> >>> and that is that - nice, simple, easy to understand. So the >>> documentation is correct. If clk_get_parent() needs to return an >>> error, it does so by returning an error-pointer, not by returning >>> NULL. >> >> Hm, so the 6 drivers that do this are OK then, if >> clk_get_parent() returns NULL? >> >> >> parent = clk_get_parent(clk); >> if (IS_ERR(parent)) { >> dev_err(cpu_dev, "Cannot get parent clock for CPU0\n"); >> clk_put(clk); >> return PTR_ERR(parent); >> } >> >> /* Get parent CPU frequency */ >> base_frequency = clk_get_rate(parent); >> >> boom? > > As I say, the premise is that only clocks where IS_ERR(clk) is true > are an error. Everything else must be treated as an acceptable clock. > > Sometimes the NULL clock is used for "I don't have a clock", and that > must not cause the API to go "boom". > > In the case of the CCF implementation, clk_get_rate(NULL) will return > 0. >
Thank you for the clarification. That is helpful.
-- ~Randy
| |