RE: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for SMMUv3 Nested device

[Shameerali Kolothum Thodi via <qemu-devel@nongnu.org>]

Hi Eric,

> -----Original Message-----
> From: Eric Auger <eric.auger@redhat.com>
> Sent: Thursday, November 14, 2024 8:42 AM
> To: Shameerali Kolothum Thodi
> <shameerali.kolothum.thodi@huawei.com>; qemu-arm@nongnu.org;
> qemu-devel@nongnu.org
> Cc: peter.maydell@linaro.org; jgg@nvidia.com; nicolinc@nvidia.com;
> ddutile@redhat.com; Linuxarm <linuxarm@huawei.com>; Wangzhou (B)
> <wangzhou1@hisilicon.com>; jiangkunkun <jiangkunkun@huawei.com>;
> Jonathan Cameron <jonathan.cameron@huawei.com>;
> zhangfei.gao@linaro.org
> Subject: Re: [RFC PATCH 2/5] hw/arm/smmuv3: Add initial support for
> SMMUv3 Nested device


> >> why did you choose not using the PLATFORM BUS infra which does that
> >> kind of binding automatically (also it provisions for dedicated MMIOs
> and
> >> IRQs). At least you would need to justify in the commit msg I think
> > Because I was not  sure how to do this binding otherwise. I couldn't find
> > any such precedence  for a  dynamic platform bus dev binding
> > MMIOs/IRQs(May be I didn't look hard). I mentioned it in cover letter.
> >
> > Could you please give me some pointers/example for this? I will also
> > take another look.
> vfio platform users such automatic binding (however you must check that
> vfio platform bus mmio and irq space is large enough for your needs).
> 
> the binding is transparently handled by
>     if (vms->platform_bus_dev) {
>         if (device_is_dynamic_sysbus(mc, dev)) {
> 
> platform_bus_link_device(PLATFORM_BUS_DEVICE(vms-
> >platform_bus_dev),
>                                      SYS_BUS_DEVICE(dev));
>         }
>     }

Ah..I see. I missed that it does that transparently.  And use 
platform_bus_get_mmio_addr() for retrieving it for ACPI/DT similar to what TPM
device is doing.

So we don't need specific entries for this device in memmap/irqmap.

I will give it a try.

Thanks,
Shameer.