Re: [PATCH v5 04/20] nubus: use bitmap to manage available slots

[Mark Cave-Ayland]

On 23/09/2021 15:16, BALATON Zoltan wrote:

> On Thu, 23 Sep 2021, Mark Cave-Ayland wrote:
> > Convert nubus_device_realize() to use a bitmap to manage available slots to 
> > allow
> > for future Nubus devices to be plugged into arbitrary slots from the command 
> > line
> > using a new qdev "slot" parameter for nubus devices.
> >
> > Update mac_nubus_bridge_init() to only allow slots 0x9 to 0xe on a Macintosh
> > machines as documented in "Desigining Cards and Drivers for the Macintosh 
> > Family".
>
> Small typo: "a Macintosh machnies", either a or s is not needed.

Thanks - I've updated this for v6.

> > Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> > ---
> > hw/nubus/mac-nubus-bridge.c         |  4 ++++
> > hw/nubus/nubus-bus.c                |  5 +++--
> > hw/nubus/nubus-device.c             | 32 +++++++++++++++++++++++------
> > include/hw/nubus/mac-nubus-bridge.h |  4 ++++
> > include/hw/nubus/nubus.h            | 13 ++++++------
> > 5 files changed, 43 insertions(+), 15 deletions(-)
> >
> > diff --git a/hw/nubus/mac-nubus-bridge.c b/hw/nubus/mac-nubus-bridge.c
> > index 7c329300b8..3f075789e9 100644
> > --- a/hw/nubus/mac-nubus-bridge.c
> > +++ b/hw/nubus/mac-nubus-bridge.c
> > @@ -18,6 +18,10 @@ static void mac_nubus_bridge_init(Object *obj)
> >
> >     s->bus = NUBUS_BUS(qbus_create(TYPE_NUBUS_BUS, DEVICE(s), NULL));
> >
> > +    /* Macintosh only has slots 0x9 to 0xe available */
> > +    s->bus->slot_available_mask = MAKE_64BIT_MASK(MAC_NUBUS_FIRST_SLOT,
> > +                                                  MAC_NUBUS_SLOT_NB);
> > +
> >     sysbus_init_mmio(sbd, &s->bus->super_slot_io);
> >     sysbus_init_mmio(sbd, &s->bus->slot_io);
> > }
> > diff --git a/hw/nubus/nubus-bus.c b/hw/nubus/nubus-bus.c
> > index f4410803ff..3cd7534864 100644
> > --- a/hw/nubus/nubus-bus.c
> > +++ b/hw/nubus/nubus-bus.c
> > @@ -86,13 +86,14 @@ static void nubus_init(Object *obj)
> >
> >     memory_region_init_io(&nubus->super_slot_io, obj, &nubus_super_slot_ops,
> >                           nubus, "nubus-super-slots",
> > -                          NUBUS_SUPER_SLOT_NB * NUBUS_SUPER_SLOT_SIZE);
> > +                          (NUBUS_SUPER_SLOT_NB + 1) * NUBUS_SUPER_SLOT_SIZE);
> >
> >     memory_region_init_io(&nubus->slot_io, obj, &nubus_slot_ops,
> >                           nubus, "nubus-slots",
> >                           NUBUS_SLOT_NB * NUBUS_SLOT_SIZE);
> >
> > -    nubus->current_slot = NUBUS_FIRST_SLOT;
> > +    nubus->slot_available_mask = MAKE_64BIT_MASK(NUBUS_FIRST_SLOT,
> > +                                                 NUBUS_SLOT_NB);
> > }
> >
> > static void nubus_class_init(ObjectClass *oc, void *data)
> > diff --git a/hw/nubus/nubus-device.c b/hw/nubus/nubus-device.c
> > index 4e23df1280..562650a05b 100644
> > --- a/hw/nubus/nubus-device.c
> > +++ b/hw/nubus/nubus-device.c
> > @@ -160,14 +160,28 @@ static void nubus_device_realize(DeviceState *dev, Error 
> > **errp)
> >     NubusDevice *nd = NUBUS_DEVICE(dev);
> >     char *name;
> >     hwaddr slot_offset;
> > -
> > -    if (nubus->current_slot < NUBUS_FIRST_SLOT ||
> > -            nubus->current_slot > NUBUS_LAST_SLOT) {
> > -        error_setg(errp, "Cannot register nubus card, not enough slots");
> > -        return;
> > +    uint16_t s;
> > +
> > +    if (nd->slot == -1) {
> > +        /* No slot specified, find first available free slot */
> > +        s = ctz32(nubus->slot_available_mask);
> > +        if (s != 32) {
> > +            nd->slot = s;
> > +        } else {
> > +            error_setg(errp, "Cannot register nubus card, no free slot "
> > +                             "available");
> > +            return;
> > +        }
> > +    } else {
> > +        /* Slot specified, make sure the slot is available */
> > +        if (!(nubus->slot_available_mask & BIT(nd->slot))) {
> > +            error_setg(errp, "Cannot register nubus card, slot %d is "
> > +                             "unavailable or already occupied", nd->slot);
> > +            return;
> > +        }
> >     }
> >
> > -    nd->slot = nubus->current_slot++;
> > +    nubus->slot_available_mask &= ~BIT(nd->slot);
> >
> >     /* Super */
> >     slot_offset = nd->slot * NUBUS_SUPER_SLOT_SIZE;
> > @@ -191,12 +205,18 @@ static void nubus_device_realize(DeviceState *dev, Error 
> > **errp)
> >     nubus_register_format_block(nd);
> > }
> >
> > +static Property nubus_device_properties[] = {
> > +    DEFINE_PROP_INT32("slot", NubusDevice, slot, -1),
> > +    DEFINE_PROP_END_OF_LIST()
> > +};
> > +
> > static void nubus_device_class_init(ObjectClass *oc, void *data)
> > {
> >     DeviceClass *dc = DEVICE_CLASS(oc);
> >
> >     dc->realize = nubus_device_realize;
> >     dc->bus_type = TYPE_NUBUS_BUS;
> > +    device_class_set_props(dc, nubus_device_properties);
> > }
> >
> > static const TypeInfo nubus_device_type_info = {
> > diff --git a/include/hw/nubus/mac-nubus-bridge.h 
> > b/include/hw/nubus/mac-nubus-bridge.h
> > index 36aa098dd4..118d67267d 100644
> > --- a/include/hw/nubus/mac-nubus-bridge.h
> > +++ b/include/hw/nubus/mac-nubus-bridge.h
> > @@ -12,6 +12,10 @@
> > #include "hw/nubus/nubus.h"
> > #include "qom/object.h"
> >
> > +#define MAC_NUBUS_FIRST_SLOT 0x9
> > +#define MAC_NUBUS_LAST_SLOT  0xe
> > +#define MAC_NUBUS_SLOT_NB    (MAC_NUBUS_LAST_SLOT - MAC_NUBUS_FIRST_SLOT + 1)
> > +
> > #define TYPE_MAC_NUBUS_BRIDGE "mac-nubus-bridge"
> > OBJECT_DECLARE_SIMPLE_TYPE(MacNubusState, MAC_NUBUS_BRIDGE)
> >
> > diff --git a/include/hw/nubus/nubus.h b/include/hw/nubus/nubus.h
> > index 89b0976aaa..988e4a2361 100644
> > --- a/include/hw/nubus/nubus.h
> > +++ b/include/hw/nubus/nubus.h
> > @@ -14,13 +14,12 @@
> > #include "qom/object.h"
> >
> > #define NUBUS_SUPER_SLOT_SIZE 0x10000000U
> > -#define NUBUS_SUPER_SLOT_NB   0x9
> > +#define NUBUS_SUPER_SLOT_NB   0xe
> >
> > #define NUBUS_SLOT_SIZE       0x01000000
> > -#define NUBUS_SLOT_NB         0xF
> > -
> > -#define NUBUS_FIRST_SLOT      0x9
> > -#define NUBUS_LAST_SLOT       0xF
> > +#define NUBUS_FIRST_SLOT      0x0
> > +#define NUBUS_LAST_SLOT       0xf
> > +#define NUBUS_SLOT_NB         (NUBUS_LAST_SLOT - NUBUS_FIRST_SLOT + 1)
> >
> > #define TYPE_NUBUS_DEVICE "nubus-device"
> > OBJECT_DECLARE_SIMPLE_TYPE(NubusDevice, NUBUS_DEVICE)
> > @@ -36,13 +35,13 @@ struct NubusBus {
> >     MemoryRegion super_slot_io;
> >     MemoryRegion slot_io;
> >
> > -    int current_slot;
> > +    uint32_t slot_available_mask;
> > };
> >
> > struct NubusDevice {
> >     DeviceState qdev;
> >
> > -    int slot;
> > +    int32_t slot;
>
> Why uint32_t? Considering its max value even uint8_t would be enough although maybe 
> invalid value would be 255 instead of -1 then. As this was added in previous patch 
> you could avoid churn here by introducing it with the right type in that patch 
> already. (But feel free to ignore it if you have no time for more changes, the 
> current version works so if you don't do another version for other reasons this 
> probably don't worth the effort alone.)

I think it makes sense to keep this signed since -1 is used for other bus 
implementations to indicate that an explicit slot hasn't been assigned. Potentially 
the slot number could be represented by an 8-bit value, however it seems there is no 
DEFINE_PROP_INT8 or DEFINE_PROP_INT16. Fortunately the slot number is restricted by 
the available slots bitmask anyhow, so this shouldn't be an issue.


ATB,

Mark.