Re: [Qemu-devel] [PATCHv2 4/8] Store IDE bus id in IDEBus structure for easy access.

[Markus Armbruster <armbru@redhat.com>]

Gleb Natapov <gleb@redhat.com> writes:

> On Wed, Nov 03, 2010 at 02:39:52PM +0100, Markus Armbruster wrote:
>> Here's a generic answer to the question "which of the device's buses is
>> this?"
>> 
>> int qbus_index(BusState *bus)
>> {
>>     BusState *b;
>>     int i, index;
>> 
>>     index = -1;
>>     i = 0;
>>     QLIST_FOREACH(b, &bus->parent->child_bus, sibling) {
>>         if (b == bus) {
>>             index = i;
>>         }
>>         i++;
>>     }
>>     assert(0 <= index && index < i);
>>     return i - 1 - index;
>> }
>> 
>> The bus created first has index 0.
>> 
>> Note that the child_bus holds the children in reverse creation order,
>> and we can't traverse it backwards.  Same problem also visible with
>> makes info qtree:
>> 
>>       dev: piix3-ide, id ""
>> [...]
>>         bus: ide.1
>>           type IDE
>>         bus: ide.0
>>           type IDE
> Isn't this too implementation dependant?

Well, it's the implementation depending on itself.

>                                          Are you against adding bus_id
> to IDEBus?

"Against" is too hard a word.  If it's a general question, I'd prefer a
general answer.

>            And will it work with ISA? I do not think IDEBus is
> added to bus->parent->child_bus in case of ISA otherwise why both
> IDEBuses have same name in isapc. Currently I have following patch
> queued. It should fix isapc case too.

You're right, it's not helpful there: two separate devices, both
providing just one bus.

>     Fix isapc IDE bus creation
>     
>     Currently we create two ide buses with the same name, so it is impossible
>     to use -device ide-drive,bus= to address all possible disks in the isapc
>     machine. Fix that by giving different names to different ide buses. Also
>     store IDE bus id in IDEBus structure for easy access.

Changing the name of the second default isa-ide device's bus to "ide.1"
is fine with me.

But with that change in place, why do we need to store the bus number?
Why can't we just use the name?

Moreover, I think the meaning of "bus number" is unclear.  See comments
inline.

> diff --git a/hw/ide/cmd646.c b/hw/ide/cmd646.c
> index ff80dd5..b2cbdbc 100644
> --- a/hw/ide/cmd646.c
> +++ b/hw/ide/cmd646.c
> @@ -257,8 +257,8 @@ static int pci_cmd646_ide_initfn(PCIDevice *dev)
>      pci_conf[PCI_INTERRUPT_PIN] = 0x01; // interrupt on pin 1
>  
>      irq = qemu_allocate_irqs(cmd646_set_irq, d, 2);
> -    ide_bus_new(&d->bus[0], &d->dev.qdev);
> -    ide_bus_new(&d->bus[1], &d->dev.qdev);
> +    ide_bus_new(&d->bus[0], &d->dev.qdev, 0);
> +    ide_bus_new(&d->bus[1], &d->dev.qdev, 1);
>      ide_init2(&d->bus[0], irq[0]);
>      ide_init2(&d->bus[1], irq[1]);
>  
> diff --git a/hw/ide/internal.h b/hw/ide/internal.h
> index 4165543..bde2664 100644
> --- a/hw/ide/internal.h
> +++ b/hw/ide/internal.h
> @@ -448,6 +448,7 @@ struct IDEBus {
>      IDEDevice *slave;
>      BMDMAState *bmdma;
>      IDEState ifs[2];
> +    uint8_t bus_id;

Why is this uint8_t?

>      uint8_t unit;
>      uint8_t cmd;
>      qemu_irq irq;
> @@ -564,7 +565,7 @@ void ide_init2_with_non_qdev_drives(IDEBus *bus, DriveInfo *hd0,
>  void ide_init_ioport(IDEBus *bus, int iobase, int iobase2);
>  
>  /* hw/ide/qdev.c */
> -void ide_bus_new(IDEBus *idebus, DeviceState *dev);
> +void ide_bus_new(IDEBus *idebus, DeviceState *dev, uint8_t bus_id);
>  IDEDevice *ide_create_drive(IDEBus *bus, int unit, DriveInfo *drive);
>  
>  #endif /* HW_IDE_INTERNAL_H */
> diff --git a/hw/ide/isa.c b/hw/ide/isa.c
> index 9b94495..b000ab8 100644
> --- a/hw/ide/isa.c
> +++ b/hw/ide/isa.c
> @@ -66,8 +66,9 @@ static const VMStateDescription vmstate_ide_isa = {
>  static int isa_ide_initfn(ISADevice *dev)
>  {
>      ISAIDEState *s = DO_UPCAST(ISAIDEState, dev, dev);
> +    static uint8_t bus_id = 0;
>  
> -    ide_bus_new(&s->bus, &s->dev.qdev);
> +    ide_bus_new(&s->bus, &s->dev.qdev, bus_id++);
>      ide_init_ioport(&s->bus, s->iobase, s->iobase2);
>      isa_init_irq(dev, &s->irq, s->isairq);
>      isa_init_ioport_range(dev, s->iobase, 8);

Works for any number of isa-ide devices.  Each one provides one IDE bus,
and the buses are numbered 0, ... in the order the isa-ide devices are
created.

> diff --git a/hw/ide/piix.c b/hw/ide/piix.c
> index 6206201..e56777f 100644
> --- a/hw/ide/piix.c
> +++ b/hw/ide/piix.c
> @@ -129,8 +129,8 @@ static int pci_piix_ide_initfn(PCIIDEState *d)
>  
>      vmstate_register(&d->dev.qdev, 0, &vmstate_ide_pci, d);
>  
> -    ide_bus_new(&d->bus[0], &d->dev.qdev);
> -    ide_bus_new(&d->bus[1], &d->dev.qdev);
> +    ide_bus_new(&d->bus[0], &d->dev.qdev, 0);
> +    ide_bus_new(&d->bus[1], &d->dev.qdev, 1);
>      ide_init_ioport(&d->bus[0], 0x1f0, 0x3f6);
>      ide_init_ioport(&d->bus[1], 0x170, 0x376);
>  

Each piix3-ide device provides two IDE buses numbered 0 and 1.

If you create multiple IDE controller devices, then the IDE bus numbers
and names clash, unless they're all isa-ide devices.

What is the IDE bus number supposed to mean?

Example: default piix3-ide plus a tertiary IDE channel
-M pc -device isa-ide,iobase=0x1e8,iobase2=0x3ee,irq=11

> diff --git a/hw/ide/qdev.c b/hw/ide/qdev.c
> index 336ffe1..220729e 100644
> --- a/hw/ide/qdev.c
> +++ b/hw/ide/qdev.c
> @@ -29,9 +29,13 @@ static struct BusInfo ide_bus_info = {
>      .size  = sizeof(IDEBus),
>  };
>  
> -void ide_bus_new(IDEBus *idebus, DeviceState *dev)
> +void ide_bus_new(IDEBus *idebus, DeviceState *dev, uint8_t bus_id)
>  {
> -    qbus_create_inplace(&idebus->qbus, &ide_bus_info, dev, NULL);
> +    char name[10];
> +
> +    snprintf(name, sizeof(name), "ide.%d", bus_id); 
> +    qbus_create_inplace(&idebus->qbus, &ide_bus_info, dev, name);
> +    idebus->bus_id = bus_id;
>  }

Incompatible change.

Before: -M pc -device isa-ide,iobase=0x1e8,iobase2=0x3ee,irq=11,id=foo
provides an IDE bus called "foo.0":

          dev: isa-ide, id "foo"
            dev-prop: iobase = 0x1e8
            dev-prop: iobase2 = 0x3ee
            dev-prop: irq = 11
            isa irq 11
            bus: foo.0
              type IDE

After: it's called "ide.0", I think.

Likely to break non-default IDE controller use.  Could be rare enough
for us not to care, I don't know.

If we need to avoid this change, then ide_bus_new() must not pass a bus
name to qbus_create_inplace() for devices added with -device/device_add.

>  
>  static int ide_qdev_init(DeviceState *qdev, DeviceInfo *base)
> diff --git a/hw/ide/via.c b/hw/ide/via.c
> index b2c7cad..cc48b2b 100644
> --- a/hw/ide/via.c
> +++ b/hw/ide/via.c
> @@ -158,8 +158,8 @@ static int vt82c686b_ide_initfn(PCIDevice *dev)
>  
>      vmstate_register(&dev->qdev, 0, &vmstate_ide_pci, d);
>  
> -    ide_bus_new(&d->bus[0], &d->dev.qdev);
> -    ide_bus_new(&d->bus[1], &d->dev.qdev);
> +    ide_bus_new(&d->bus[0], &d->dev.qdev, 0);
> +    ide_bus_new(&d->bus[1], &d->dev.qdev, 1);
>      ide_init2(&d->bus[0], isa_reserve_irq(14));
>      ide_init2(&d->bus[1], isa_reserve_irq(15));
>      ide_init_ioport(&d->bus[0], 0x1f0, 0x3f6);
> diff --git a/hw/pc_piix.c b/hw/pc_piix.c
> index 3d07ce5..cec6c9b 100644
> --- a/hw/pc_piix.c
> +++ b/hw/pc_piix.c
> @@ -163,7 +163,7 @@ static void pc_init1(ram_addr_t ram_size,
>              ISADevice *dev;
>              dev = isa_ide_init(ide_iobase[i], ide_iobase2[i], ide_irq[i],
>                                 hd[MAX_IDE_DEVS * i], hd[MAX_IDE_DEVS * i + 1]);
> -            idebus[i] = qdev_get_child_bus(&dev->qdev, "ide.0");
> +            idebus[i] = qdev_get_child_bus(&dev->qdev, i ? "ide.1" : "ide.0");
>          }
>      }