Re: [PATCH 0/9] hw: Use QOM alias properties and few QOM/QDev cleanups

[Philippe Mathieu-Daudé]

On 6/2/23 00:29, Mark Cave-Ayland wrote:
> On 03/02/2023 11:36, Philippe Mathieu-Daudé wrote:
>
> > These patches are extracted from a QOM/QDev refactor series,
> > so they are preliminary cleanups noticed while working on it:
> >
> > - Use correct type when calling qdev_prop_set_xxx()
> > - Unify some qdev properties in MIPS models
> > - Replace intermediate properties by link properties
> > - Remove DEFINE_PROP_DMAADDR() macro which is used one time
> > - Use qdev_realize_and_unref() instead of open-coding it
> >
> > Philippe Mathieu-Daudé (9):
> >    hw/i386/sgx: Do not open-code qdev_realize_and_unref()
> >    hw/ppc/sam460ex: Correctly set MAL properties
> >    hw/arm/nrf51: QOM-alias 'flash-size' property in SoC object
> >    hw/arm/fsl-imx: QOM-alias 'phy-num' property in SoC object
> >    hw/usb/hcd-ohci: Include missing 'sysbus.h' header
> >    hw/display/sm501: QOM-alias 'dma-offset' property in chipset object
> >    hw/qdev: Remove DEFINE_PROP_DMAADDR() and 'hw/qdev-dma.h'
> >    hw/mips: Declare all length properties as unsigned
> >    hw/mips/itu: Pass SAAR using QOM link property
> >
> >   hw/arm/fsl-imx25.c           |  3 +--
> >   hw/arm/fsl-imx6.c            |  3 +--
> >   hw/arm/fsl-imx6ul.c          |  8 ++++----
> >   hw/arm/fsl-imx7.c            | 12 ++++++------
> >   hw/arm/microbit.c            |  5 ++++-
> >   hw/arm/nrf51_soc.c           | 10 +---------
> >   hw/display/sm501.c           | 22 +++++++++++-----------
> >   hw/i386/sgx.c                |  5 ++---
> >   hw/intc/mips_gic.c           |  4 ++--
> >   hw/mips/boston.c             |  2 +-
> >   hw/mips/cps.c                | 35 ++++++++++++-----------------------
> >   hw/mips/malta.c              |  2 +-
> >   hw/misc/mips_cmgcr.c         |  2 +-
> >   hw/misc/mips_itu.c           | 30 ++++++++++++++++++++----------
> >   hw/nvram/nrf51_nvm.c         |  6 +++++-
> >   hw/ppc/sam460ex.c            |  4 ++--
> >   hw/sh4/r2d.c                 |  2 +-
> >   hw/usb/hcd-ohci-pci.c        |  1 -
> >   hw/usb/hcd-ohci.c            |  3 +--
> >   hw/usb/hcd-ohci.h            |  1 +
> >   include/hw/arm/fsl-imx25.h   |  1 -
> >   include/hw/arm/fsl-imx6.h    |  1 -
> >   include/hw/arm/fsl-imx6ul.h  |  2 --
> >   include/hw/arm/fsl-imx7.h    |  1 -
> >   include/hw/arm/nrf51_soc.h   |  1 -
> >   include/hw/intc/mips_gic.h   |  4 ++--
> >   include/hw/misc/mips_cmgcr.h |  2 +-
> >   include/hw/misc/mips_itu.h   |  9 ++++-----
> >   include/hw/qdev-dma.h        | 16 ----------------
> >   29 files changed, 84 insertions(+), 113 deletions(-)
> >   delete mode 100644 include/hw/qdev-dma.h
>
> I must admit to being slightly nervous about using QOM alias properties 
> in this way, simply because you start creating implicit dependencies 
> between QOM objects. How would this work when trying to build machines 
> from configuration files and/or the monitor? Or are the changes 
> restricted to container devices i.e. those which consist of in-built 
> child devices?

The latter. All parents forward a property to a contained child.

The parent forwarding property is replaced by a link into the child,
so accessing the parent property transparently access the child one.

The dependencies are already explicit. We can not create a parent
without its children (the children creation is implicit when we
create the parent object).


I thought this was the canonical QOM alias properties use. What is
the normal use then?