Re: [libvirt] [PATCH v3 01/12] conf: Add definitions for 'uid' and 'fid' PCI address attributes
在 2018/8/16 下午10:38, Andrea Bolognani 写道:
On Tue, 2018-08-07 at 17:10 +0800, Yi Min Zhao wrote:
> +typedef struct _virZPCIDeviceAddress virZPCIDeviceAddress;
> +typedef virZPCIDeviceAddress *virZPCIDeviceAddressPtr;
> +struct _virZPCIDeviceAddress {
> + unsigned int zpci_fid;
> + unsigned int zpci_uid;
> + bool fid_assigned;
> + bool uid_assigned;
> +};
A couple of questions about the approach here, one of which I have
mentioned already and one of which I probably haven't (my bad):
* do you really need to have separate booleans tracking whether
or not either id has been assigned? Wouldn't the same approach
as virPCIDeviceAddressIsEmpty() work, eg. consider the address
absent if both are zero and present otherwise?
It's OK for uid. But for
fid, zero is a valid value, so we need a bool
to track its assignment.
If we add a boolean for fid, why not also add another one for uid to
keep consistency?
This also makes code easy to read and obvious. It doesn't waste much
memory space.
* especially if you don't need the additional booleans, would it
be preferable to just add the two ids to the existing struct
instead of declaring a new one that you'll have to allocate
and make sure it's not NULL before accessing it? Again, I seem
to remember Laine feeling somewhat strongly about the topic.
For other
platforms, is it OK to waste this unused memory (of course,
it's little) ?
Cosmetic issues:
* uid should be listed before fid;
* the zpci_ prefix is unnecessary if you have a separate struct
that contains "ZPCI" in the name. But see above :)