[ipxe-devel] [PATCH v2 2/3] [virtio] Renumber virtio_pci_region flags

[Ladi Prosek]

On Mon, May 2, 2016 at 4:21 PM, Marcel Apfelbaum <marcel at redhat.com> wrote:
> On 05/02/2016 04:11 PM, Ladi Prosek wrote:
>>
>> Some of the regions may end up being unmapped, either because
>> they are optional or because the attempt to map them has failed.
>> Region types starting at 0 didn't make it easy to test for this
>> condition.
>>
>> This commit adds VIRTIO_PCI_REGION_NONE with the value of 0
>> and bumps the valid region types up by 1.
>>
>> Signed-off-by: Ladi Prosek <lprosek at redhat.com>
>> ---
>>   src/include/ipxe/virtio-pci.h | 8 +++++---
>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/src/include/ipxe/virtio-pci.h b/src/include/ipxe/virtio-pci.h
>> index c7452c8..ec8efaa 100644
>> --- a/src/include/ipxe/virtio-pci.h
>> +++ b/src/include/ipxe/virtio-pci.h
>> @@ -106,12 +106,14 @@ struct virtio_pci_region {
>>
>>   /* How to interpret the base field */
>>   #define VIRTIO_PCI_REGION_TYPE_MASK  0x00000003
>> +/* The region is unused */
>> +#define VIRTIO_PCI_REGION_NONE       0x00000000
>>   /* The base field is a memory address */
>> -#define VIRTIO_PCI_REGION_MEMORY     0x00000000
>> +#define VIRTIO_PCI_REGION_MEMORY     0x00000001
>>   /* The base field is a port address */
>> -#define VIRTIO_PCI_REGION_PORT       0x00000001
>> +#define VIRTIO_PCI_REGION_PORT       0x00000002
>>   /* The base field is an offset within the PCI bar */
>> -#define VIRTIO_PCI_REGION_PCI_CONFIG 0x00000002
>> +#define VIRTIO_PCI_REGION_PCI_CONFIG 0x00000003
>
>
>
> Is OK if you are not interested to use the flags as bits.
> Otherwise you may want to give VIRTIO_PCI_REGION_PCI_CONFIG the value 4.

Yes, I just wanted to reserve 2 bits out of the flags field for this.
The flags are exclusive so no need to combine them and assign one bit
to each.

> And I also didn't see you used the new VIRTIO_PCI_REGION_NONE flag.
> I suggest to wait with this patch until you will actually use it.

Patch 3/3 has a dependency on the new numbers in
virtnet_uses_region_type as vdev->device may not be mapped and flags
be 0. The old numbers were chosen pretty unfortunately (my fault) so
you couldn't tell an unused region and a memory region apart.

You're right that VIRTIO_PCI_REGION_NONE is not used. I included it
for completeness, to be explicit about what 0 means. I can remove it
if you'd prefer that.

Thanks,
Ladi

>
> Thanks,
> Marcel
>
>>       unsigned flags;
>>   };
>>
>>
>