proposal: require ivar accessors to succeed

[Conrad Meyer]

Seems like a good idea to me.

Best, Conrad

On Sun, May 26, 2019 at 10:45 PM Andriy Gapon <avg at freebsd.org> 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.
> Thank you.
> --
> Andriy Gapon
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