Re: [Xen-devel] [PATCH v2 11/18] libxl: synchronise configuration when we hotplug a device

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2014-07-30 at 19:23 +0100, Wei Liu wrote:
> As those routines are called both during domain creation and device
> hotplug, we add a flag to indicate whether we need to update JSON
> config. This flag is only set to true when we hotplug a device. We
> cannot update JSON config during domain creation as JSON config is
> committed to disk only when domain creation finishes.

Rather than carry a flag around did you consider just checking for the
presence of the file? I think you indicated in an earlier patch that you
were going to treat lack of the file as meaning creation/destruction was
happening.


> + * They take 6 parameters:
> + *  type:    the type of the device, say nic, vtpm, disk, pci etc
> + *  ptr:     the pointer to array inside libxl_domain_config

To the array or to a specific element of the array? I think the latter.
You might also want to indicate that the ptr must be of type
libxl_device_#type?

> + *  cnt:     the counter of array

I think you either mean index or length, I suspect the former?

> + *  domid:   domain id of target domain
> + *  dev:     the device that is to be added / removed / updated
> + *  compare: the COMPARE_* macro used to compare @dev's identifier to
> + *           those in the array pointed to by @ptr
> + *
> + * Return 0 if no error occurs, ERROR_* otherwise.
> + *
> + * For most device types (nic, vtpm), the array name @ptr and array
> + * counter @cnt can be derived from @type, pci device being the
> + * exception, hence we need to have @ptr and @cnt.

You could get away with a single variable naming the Array ("nics",
"pcidevs") to which you paste num_ on the front when you need cnt.

Ian.


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