Re: [PATCH 09/13] hw/ide/piix: Disuse isa_get_irq()

[Mark Cave-Ayland]

On 22/04/2023 16:07, Bernhard Beschow wrote:

> isa_get_irq() asks for an ISADevice which piix-ide doesn't provide.
> Passing a NULL pointer works but causes the isabus global to be used
> then. By fishing out TYPE_ISA_BUS from the QOM tree it is possible to
> achieve the same as using isa_get_irq().
>
> This is an alternative solution to commit 9405d87be25d 'hw/ide: Fix
> crash when plugging a piix3-ide device into the x-remote machine' which
> allows for cleaning up the ISA API while keeping PIIX IDE functions
> user-createable.
>
> Signed-off-by: Bernhard Beschow <shentey@gmail.com>
> ---
>   hw/ide/piix.c | 23 ++++++++++++++++++++---
>   1 file changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/hw/ide/piix.c b/hw/ide/piix.c
> index 6942b484f9..a3a15dc7db 100644
> --- a/hw/ide/piix.c
> +++ b/hw/ide/piix.c
> @@ -104,7 +104,8 @@ static void piix_ide_reset(DeviceState *dev)
>       pci_set_byte(pci_conf + 0x20, 0x01);  /* BMIBA: 20-23h */
>   }
>   
> -static bool pci_piix_init_bus(PCIIDEState *d, unsigned i, Error **errp)
> +static bool pci_piix_init_bus(PCIIDEState *d, unsigned i, ISABus *isa_bus,
> +                              Error **errp)
>   {
>       static const struct {
>           int iobase;
> @@ -124,7 +125,8 @@ static bool pci_piix_init_bus(PCIIDEState *d, unsigned i, 
> Error **errp)
>                            object_get_typename(OBJECT(d)), i);
>           return false;
>       }
> -    ide_bus_init_output_irq(&d->bus[i], isa_get_irq(NULL, 
> port_info[i].isairq));
> +    ide_bus_init_output_irq(&d->bus[i],
> +                            isa_bus_get_irq(isa_bus, port_info[i].isairq));

I don't think is the right solution here, since ultimately we want to move the IRQ 
routing out of the device itself and into the PCI-ISA bridge. I'd go for the same 
solution as you've done for VIA IDE in patch 2, i.e. update the PIIX interrupt 
handler to set the legacy_irqs in PCIIDEState, and then wire them up to the ISA IRQs 
14 and 15 similar to as Phil as done in his patches:

https://patchew.org/QEMU/20230302224058.43315-1-philmd@linaro.org/20230302224058.43315-4-philmd@linaro.org/

https://patchew.org/QEMU/20230302224058.43315-1-philmd@linaro.org/20230302224058.43315-5-philmd@linaro.org/

This also reminds me, given that the first patch above is doing wiring in pc_init1() 
then we are still missing part of your tidy-up series :/

>       bmdma_init(&d->bus[i], &d->bmdma[i], d);
>       ide_bus_register_restart_cb(&d->bus[i]);
> @@ -136,14 +138,29 @@ static void pci_piix_ide_realize(PCIDevice *dev, Error 
> **errp)
>   {
>       PCIIDEState *d = PCI_IDE(dev);
>       uint8_t *pci_conf = dev->config;
> +    ISABus *isa_bus;
> +    bool ambiguous;
>   
>       pci_conf[PCI_CLASS_PROG] = 0x80; // legacy ATA mode
>   
>       bmdma_init_ops(d, &piix_bmdma_ops);
>       pci_register_bar(dev, 4, PCI_BASE_ADDRESS_SPACE_IO, &d->bmdma_ops);
>   
> +    isa_bus = ISA_BUS(object_resolve_path_type("", TYPE_ISA_BUS, &ambiguous));
> +    if (ambiguous) {
> +        error_setg(errp,
> +                   "More than one ISA bus found while %s supports only one",
> +                   object_get_typename(OBJECT(d)));
> +        return;
> +    }
> +    if (!isa_bus) {
> +        error_setg(errp, "No ISA bus found while %s requires one",
> +                   object_get_typename(OBJECT(d)));
> +        return;
> +    }

Again I think this should go away with using PCIIDEState's legacy_irqs, since you 
simply let the board wire them up to the ISABus (or not) as required.

>       for (unsigned i = 0; i < 2; i++) {
> -        if (!pci_piix_init_bus(d, i, errp)) {
> +        if (!pci_piix_init_bus(d, i, isa_bus, errp)) {
>               return;
>           }
>       }


ATB,

Mark.