Re: [Xen-devel] [PATCH 0/3] libxl: add framework for device types

[Juergen Gross <jgross@xxxxxxxx>]

On 06/07/16 14:47, Ian Jackson wrote:
> Juergen Gross writes ("Re: [PATCH 0/3] libxl: add framework for device 
> types"):
>> On 06/07/16 13:04, Ian Jackson wrote:
>>>> +    for (i = 0; i < d_config->num_pcidevs; i++) {
>>>> +        rc = libxl__device_pci_add(gc, domid, &d_config->pcidevs[i], 1);
>>>> +        if (rc < 0) {
>>>> +            LOG(ERROR, "libxl_device_pci_add failed: %d", rc);
>>>> +            goto out;
>>>> +        }
>>>> +    }
>>>> +
>>>
>>> And there is similar code in 3/3 for dtdevs.  Could that be lifted
>>> away somehow ?  (You'd have to take some care about the types, sadly;
>>> ie, I think libxl__device_pci_add might have to start to take a
>>> void*; maybe some macros could make things typesafe?)
>>
>> I thought about this idea already. I think we would end up with more
>> code which would be rather unpleasant to read. Main reason is the
>> need for a dtdev wrapper function and the pci backend creation.
> 
> I'm not sure what you mean by dtdev wrapper function.

The loop for dtdev calls a xc_ function with different parameters than
the one for pci. We'd need a libxl__device_dtdev_add() wrapper function
to do the xc_ call.

> As for pci backend, there could be a separate hook for "after adding
> all devices of this type".

Right. And summing up the additional hooks and queries whether they
are specified sums up to more overhead than the current version.

> But if you don't think this is feasible I won't insist on it.  The
> approach you have is already a big improvement.

Thanks.

I'm planning to add more to it (e.g. I'd like to get rid of the
MERGE() macro in libxl_retrieve_domain_configuration() in favor of a
device type hook in order to be able to have _all_ stuff for one type
in one source file.


Juergen

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