Re: [PATCH v6 10/12] watchdog: add gpio watchdog driver

Wolfgang Denk
2021-08-19T14:16:28Z

Dear Tom,

In message <20210819130806.GW858@bill-the-cat> you wrote:
>
> > So we have now a policy to wave through code, and ask others to
> > clean it up later? That's ... sad.
>
> No, we continue to have the policy of expecting reviewers to follow the
> whole discussion and relevant subsystems.

Once upon a time there has also been a policy that if a function
might return error codes, these need to be checked and handled.

> Changing _every_ caller of dev_get_priv to check for NULL and
> then, what? is clearly not the right answer.

Then what is the right answer in your opinion?

I mean, look at the implementation of dev_get_priv():

628 void *dev_get_priv(const struct udevice *dev)
629 {
630 if (!dev) {
631 dm_warn("%s: null device\n", __func__);
632 return NULL;
633 }
634
635 return dm_priv_to_rw(dev->priv_);
636 }

If there is guaranteed no way that dev_get_priv() can return a NULL
pointer, that means that it must be guaranteed that the "dev"
argument can never be a NULL pointer, either. So why do we check it
at all?

The same applies for all functions in "drivers/core/device.c" - they
all check for valid input parameters, like any code should do.

> If you think you see a problem here please go audit the DM code
> itself more and propose some changes.

I can see that the DM code itself implements proper error checking
and reporting; it's the callers where negligent code prevails.

If you are consequent, you must decide what you want:

- Either we want robust and reliable code - then we have to handle
the error codes which functions like dev_get_priv() etc. return.

- Or you don't care about software quality, then we can omit such
handling, but then it would also be consequent to remove all the
error checking from "drivers/core/device.c" etc. - hey, that would
even save a few hundred bytes of code size.

Sugarcoating code which fails to handle error codes because "these
errors can never happen" does not seem to be a clever approach to
software engineering to me.

I stop here. You know my opinion. You are the maintainer.

Wolfgang Denk

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