[PATCH 1/7] clk: Make rfree return void

[Simon Glass]

Hi Sean,

On Tue, 1 Feb 2022 at 07:49, Sean Anderson <seanga2 at gmail.com> wrote:
>
> On 1/27/22 4:35 PM, Simon Glass wrote:
> > Hi Sean,
> >
> > On Thu, 27 Jan 2022 at 08:43, Sean Anderson <seanga2 at gmail.com> wrote:
> >>
> >> On 1/27/22 10:05 AM, Simon Glass wrote:
> >>> Hi Sean,
> >>>
> >>> On Sat, 15 Jan 2022 at 15:25, Sean Anderson <seanga2 at gmail.com> wrote:
> >>>>
> >>>> When freeing a clock there is not much we can do if there is an error, and
> >>>> most callers do not actually check the return value. Even e.g. checking to
> >>>> make sure that clk->id is valid should have been done in request() in the
> >>>> first place (unless someone is messing with the driver behind our back).
> >>>> Just return void and don't bother returning an error.
> >>>>
> >>>> Signed-off-by: Sean Anderson <seanga2 at gmail.com>
> >>>> ---
> >>>>
> >>>>    drivers/clk/clk-uclass.c  | 7 +++----
> >>>>    drivers/clk/clk_sandbox.c | 6 +++---
> >>>>    include/clk-uclass.h      | 8 +++-----
> >>>>    3 files changed, 9 insertions(+), 12 deletions(-)
> >>>>
> >>>
> >>> We have the same thing in other places too, but I am a little worried
> >>> about removing error checking. We try to avoid checking arguments too
> >>> much in U-Boot, due to code-size concerns, so I suppose I agree that
> >>> an invalid clk should be caught by a debug assertion rather than a
> >>> full check. But with driver model we have generally added an error
> >>> return to every uclass method, for consistency and to permit returning
> >>> error information if needed.
> >>>
> >>> Regards,
> >>> Simon
> >>>
> >>
> >> So there are a few reasons why I don't think a return value is useful
> >> here. To illustrate this, consider a typical user of the clock API:
> >>
> >>          struct clk a, b;
> >>
> >>          ret = clk_get_by_name(dev, "a", &a);
> >>          if (ret)
> >>                  return ret;
> >>
> >>          ret = clk_get_by_name(dev, "b", &b);
> >>          if (ret)
> >>                  goto free_a;
> >>
> >>          ret = clk_set_rate(&a, 5000000);
> >>          if (ret)
> >>                  goto free_b;
> >>
> >>          ret = clk_enable(&b);
> >>
> >> free_b:
> >>          clk_free(&b);
> >> free_a:
> >>          clk_free(&a);
> >>          return ret;
> >>
> >> - Because a and b are "thick pointers" they do not need any cleanup to
> >>     free their own resources. The only cleanup might be if the clock
> >>     driver has allocated something in clk_request (more on this below)
> >> - By the time we call clk_free, the mutable portions of the function
> >>     have already completed. In effect, the function has succeeded,
> >>     regardless of whether clk_free fails. Additionally, we cannot take any
> >>     action if it fails, since we still have to free both clocks.
> >> - clk_free occurs during the error path of the function. Even if it
> >>     errored, we do not want to override the existing error from one of the
> >>     functions doing "real" work.
> >>
> >> The last thing is that no clock driver actually does anything in rfree.
> >> The only driver with this function is the sandbox driver. I would like
> >> to remove the function altogether. As I understand it, the existing API
> >> is inspired by the reset drivers, so I would like to review its usage in
> >> the reset subsystem before removing it for the clock subsystem. I also
> >> want to make some changes to how rates and enables/disables are
> >> calculated which might provide a case for rfree. But once that is
> >> complete I think there will be no users still.
> >
> > What does this all look like in Linux?
>
> Their equivalent (clk_put) returns void, and generally so do most other
> cleanup functions, since .device_remove also returns void.

We really cannot ignore errors from device_remove().

Anyway I think what you say about the 'thick pointer' makes sense. But
my expectation was that removing a clock might turn off a clock above
it in the tree, for example.

Regards,
Simon