Re: [for-8.0] hw/i2c/allwinner-i2c: Fix subclassing of TYPE_AW_I2C_SUN6I

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> In commit 8461bfdca9c we added the TYPE_AW_I2C_SUN6I, which is a
> minor variant of the TYPE_AW_I2C device.  However, we didn't quite
> get the class hierarchy right.  We made the new TYPE_AW_I2C_SUN6I a
> subclass of TYPE_SYS_BUS_DEVICE, which means that you can't validly
> use a pointer to this object via the AW_I2C() cast macro, which
> insists on having something that is an instance of TYPE_AW_I2C or
> some subclass of that type.
>
> This only causes a problem if QOM cast macro debugging is enabled;
> that is supposed to be on by default, but a mistake in the meson
> conversion in commit c55cf6ab03f4c meant that it ended up disabled by
> default, and we didn't catch this bug.
>
> Fix the problem by arranging the classes in the same way we do for
> TYPE_PL011 and TYPE_PL011_LUMINARY in hw/char/pl011.c -- make the
> variant class be a subclass of the "normal" version of the device.
>
> This was reported in
> https://gitlab.com/qemu-project/qemu/-/issues/1586 but this fix alone
> isn't sufficient, as there is a separate cast-related issue in the
> CXL code in pci_expander_bridge.c.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro