proposal: require ivar accessors to succeed

[Bjoern A. Zeeb]

On 27 May 2019, at 5:44, Andriy Gapon wrote:

> __BUS_ACCESSOR() macro is used to define accessors to bus IVAR 
> variables.
> Unfortunately, accessors defined in such a fashion completely ignore 
> return
> values of BUS_READ_IVAR() and BUS_WRITE_IVAR() method calls.  There is 
> no way to
> see if a call is successful.  Typically, this should not be a problem 
> as a
> device driver targets a specific bus (sometimes, buses) and it should 
> know what
> IVARs the bus has.  So, the driver should make only those IVAR calls 
> that are
> supposed to always succeed on the bus.
> But sometimes things can go wrong as with everything else.
>
> So, I am proposing to add some code to __BUS_ACCESSOR to verify the 
> success.
> For example, we can panic when a call fails.  The checks could be 
> under
> INVARIANTS or under DIAGNOSTICS or under a new kernel option.
> A less drastic option is to print a warning message on an error.
>
> This is mostly intended to help driver writers and maintainers.
>
> Opinions, suggestions, etc are welcome.

What about “fixing” the KPI (possibly adding a 2nd one), deprecating 
the old one, and (slowly over time) migrating old stuff over?

/bz