[Qemu-devel] Re: [PATCH] piix: use pci_config_set_prog_interface()

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Dec 28, 2010 at 07:48:23PM +0100, Sebastian Herbszt wrote:
> Michael S. Tsirkin wrote:
> >On Tue, Dec 28, 2010 at 05:24:06PM +0100, Sebastian Herbszt wrote:
> >>Michael S. Tsirkin wrote:
> >>>On Mon, Dec 20, 2010 at 10:18:01PM +0100, Sebastian Herbszt wrote:
> >>>>Use pci_config_set_prog_interface().
> >>>>
> >>>>Signed-off-by: Sebastian Herbszt <herbszt@gmx.de>
> >>>
> >>>Since I was asked explicitly - I don't have a problem
> >>>with these changes: both class and prog interface.
> >>>However, they aren't all that useful in themselves.
> >>>
> >>>For class, what I would like to see is a system where
> >>>the device class is put in the qdev info table,
> >>>and where -device ?
> >>>(and hopefully the legacy -help, -nic etc as well)
> >>>use this information.
> >>
> >>I am not sure if you mean something like the patch below.
> >
> >Not exactly
> >
> >- I'd like to keep the pci_config_set_class in the devices,
> > just make it do an assert.
> 
> Assert on which condition?

That PCI class matches device type defined in qdev.
This will serve to verify that all devices are converted properly.

> >- Nics already have DEFINE_NIC_PROPERTIES - can this be used somehow?
> > Same for other devices ...
> 
> We got DEFINE_NIC_PROPERTIES and DEFINE_BLOCK_PROPERTIES.
> Something like DEFINE_PCI_PROPERTIES could be introduced, but i am not sure

This shouldn't have to do anything with PCI.
We should define the device type as NIC,
PCI class can be derived from that.

> which device properties it should hold (vendor_id, device_id, class, etc?).
> Those will then be user-modifiable with e.g. -device e1000,pci_class=1234.
> 
> Sebastian

Why is this helpful?
- tweaking class will just break guests
- binary representation is unfriendly, let's not require users to read
  pci spec just to run qemu.

I can imagine some useful features implemented by sticking the type in qdev:
- -device ? would sort devices by type and print the type,
- something like this for qtree etc
- -help would get all e.g. nic models from qdev,
-  allow easy to remember aliases with per-type scope (e.g.
   -device virtio,type=nic to be equivalent to -device virtio-net-pci)
- filter (for device ?, qtree etc) system devices that user has no business
   tweaking (could be type=system or something like that)

> diff --git a/hw/e1000.c b/hw/e1000.c
> index af101bd..e302703 100644
> --- a/hw/e1000.c
> +++ b/hw/e1000.c
> @@ -1171,6 +1171,7 @@ static PCIDeviceInfo e1000_info = {
>     .romfile    = "pxe-e1000.bin",
>     .qdev.props = (Property[]) {
>         DEFINE_NIC_PROPERTIES(E1000State, conf),
> +        DEFINE_PROP_UINT16("pci_class", E1000State, dev.class, PCI_CLASS_NETWORK_ETHERNET),
>         DEFINE_PROP_END_OF_LIST(),
>     }
> };
> diff --git a/hw/pci.c b/hw/pci.c
> index ef00d20..06bbf04 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -1620,6 +1620,9 @@ static int pci_qdev_init(DeviceState *qdev, DeviceInfo *base)
>                                      info->is_bridge);
>     if (pci_dev == NULL)
>         return -1;
> +
> +    pci_config_set_class(pci_dev->config, pci_dev->class);
> +
>     rc = info->init(pci_dev);
>     if (rc != 0) {
>         do_pci_unregister_device(pci_dev);
> diff --git a/hw/pci.h b/hw/pci.h
> index 17744dc..5dc9053 100644
> --- a/hw/pci.h
> +++ b/hw/pci.h
> @@ -189,6 +189,9 @@ struct PCIDevice {
>     char *romfile;
>     ram_addr_t rom_offset;
>     uint32_t rom_bar;
> +
> +    /* class */

Please don't copy code into comments verbatim.

> +    uint16_t class;

Ugh. We have class in config already.

> };
> 
> PCIDevice *pci_register_device(PCIBus *bus, const char *name,
>