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

[Simon Glass]

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?

Regards,
Simon