On Wed, 27 Apr 2022 at 19:29, Leif Lindholm <quic_llind...@quicinc.com> wrote: > > The sbsa-ref machine is continuously evolving. Some of the changes we > want to make in the near future, to align with real components (e.g. > the GIC-700), will break compatibility for existing firmware. > > Introduce two new properties to the DT generated on machine generation: > - machine-version-major > To be incremented when a platform change makes the machine > incompatible with existing firmware. > - machine-version-minor > To be incremented when functionality is added to the machine > without causing incompatibility with existing firmware. > to be reset to 0 when machine-version-major is incremented. > > These properties are both introduced with the value 0. > (Hence, a machine where the DT is lacking these nodes is equivalent > to version 0.0.) > > Signed-off-by: Leif Lindholm <quic_llind...@quicinc.com> > Cc: Peter Maydell <peter.mayd...@linaro.org> > Cc: Radoslaw Biernacki <r...@semihalf.com> > Cc: Cédric Le Goater <c...@kaod.org> > --- > hw/arm/sbsa-ref.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/hw/arm/sbsa-ref.c b/hw/arm/sbsa-ref.c > index 2387401963..e05f6056c7 100644 > --- a/hw/arm/sbsa-ref.c > +++ b/hw/arm/sbsa-ref.c > @@ -190,6 +190,9 @@ static void create_fdt(SBSAMachineState *sms) > qemu_fdt_setprop_cell(fdt, "/", "#address-cells", 0x2); > qemu_fdt_setprop_cell(fdt, "/", "#size-cells", 0x2); > > + qemu_fdt_setprop_cell(fdt, "/", "machine-version-major", 0); > + qemu_fdt_setprop_cell(fdt, "/", "machine-version-minor", 0);
Seems reasonable to me, but I think: * we should say explicitly that the hardware version defined by these values has nothing to do with QEMU versioned machine types (and is more akin to a hardware motherboard revision A/B/C kind of thing), and maybe that it's not aligned with any specification version number either? * we should perhaps say that on real hardware this information would be more commonly passed to firmware as part of some sort of revision ID register, but that for sbsa-ref we put it in the DTB for convenience since we already use that to tell firmware a few things about the emulated hardware * at least some of this should be in a comment as well as the commit message, so nobody in future decides this should be "tidied up" to be a versioned machine type thanks -- PMM
