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

["Sebastian Herbszt" <herbszt@gmx.de>]

Michael S. Tsirkin wrote:
> 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.

So you want to introduce a device property like "device_type" and set it to "NIC" and
then translate "NIC" to the correct PCI class code. Are you sure this is unambiguous?
"NIC" could be ethernet or token ring. A generic name like "HBA" could translate to even
more codes (scsi, ide, raid, sata, ...).

>> 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.

"pci_class" is optional. I just wanted to show that qdev device properties are
user-modifiable and i didn't find a way to prevent this.

> 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)

Is this just a virtio problem?

> - 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.

But i could not get qdev to use it.

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

Sebastian