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Re: [PATCH v7 0/8] Pegasos2 emulation

From: BALATON Zoltan
Subject: Re: [PATCH v7 0/8] Pegasos2 emulation
Date: Tue, 16 Mar 2021 15:48:04 +0100 (CET)

Another arrempt to explain patch 1. This is the via-superio class that's a subclass of ISA superio:


#define TYPE_VIA_SUPERIO "via-superio"

struct ViaSuperIOState {
    ISASuperIODevice superio;
    uint8_t regs[0x100];
    const MemoryRegionOps *io_ops;
    MemoryRegion io;
    MemoryRegion *serial_io[SUPERIO_MAX_SERIAL_PORTS];


static void via_superio_realize(DeviceState *d, Error **errp)
    ViaSuperIOState *s = VIA_SUPERIO(d);
    ISASuperIOClass *ic = ISA_SUPERIO_GET_CLASS(s);
    Error *local_err = NULL;
    int i;

    ic->parent_realize(d, &local_err);
    if (local_err) {
        error_propagate(errp, local_err);
    /* Grab io regions of serial devices so we can control them */
    for (i = 0; i < ic->serial.count; i++) {
        ISADevice *sd = s->superio.serial[i];
        MemoryRegion *io = isa_address_space_io(sd);
        MemoryRegion *mr = find_subregion(sd, io, sd->ioport_id);
        if (!mr) {
            error_setg(errp, "Could not get io region for serial %d", i);
        s->serial_io[i] = mr;

    memory_region_init_io(&s->io, OBJECT(d), s->io_ops, s, "via-superio", 2);
    memory_region_set_enabled(&s->io, false);
    /* The floppy also uses 0x3f0 and 0x3f1 but this seems to work anyway */
    memory_region_add_subregion(isa_address_space_io(ISA_DEVICE(s)), 0x3f0,

In realize we grab pointers to the MemoryRegions of the isa-serial devices created by the ISA superio class. This is ISA superio:



struct ISASuperIODevice {
    /*< private >*/
    ISADevice parent_obj;
    /*< public >*/

    ISADevice *parallel[MAX_PARALLEL_PORTS];
    ISADevice *floppy;
    ISADevice *kbc;
    ISADevice *ide;

The serial members we access are even public so this should be OK (other models to that too) but we need to get their MemoryRegion as we need to configure that based on VIA superio registers. ISADevice is defined in:


but it does not store a reference to its memory regions:

struct ISADevice {
    /*< private >*/
    DeviceState parent_obj;
    /*< public >*/

    int8_t isairq[2];      /* -1 = unassigned */
    int nirqs;
    int ioport_id;

only an ioport_id which is the address of its first io region so we have to get the actual MemoryRegion based on that. This works for isa-serial that has a single mem region but would not for parallel or FDC that have multiple regions. Those are created with isa_register_portio_list() I think but we don't care about parallel and FDC only about serial.

This may be possible to clean up but that would need changes to ISA emulation that I don't want to change so the patch tries to achieve what's needed without changing how ISA devices are emulated currently. I think the solution proposed in patch 1 is relatively clean and by not changing anything than vt82c686 it avoids any possible breakage to other machines using ISA devices so unless there's a reason not to accept it this should solve the problem and allow pegasos2 firmware to boot.


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