[libvirt] [PATCHv2 2/8] doc: schema: Add basic documentation for the virtual RNG device support

Peter Krempa pkrempa at redhat.com
Mon Feb 25 22:02:31 UTC 2013


On 02/25/13 22:20, Peter Krempa wrote:
> On 02/25/13 22:01, Eric Blake wrote:
>> On 02/25/2013 02:08 AM, Peter Krempa wrote:
>>> On 02/22/13 19:20, Eric Blake wrote:
>>>> On 02/21/2013 07:47 AM, Peter Krempa wrote:
>>>>> This patch documents XML elements used for (basic) support of virtual
>>>>> RNG devices.
>>>>>
>>>>>
>>>>> For the slightly more advanced EGD backend:
>>>>>     <devices>
>>>>>       <rng model='virtio'>
>>>>>         <backend model='egd' type='udp'>
>>>>>           <!-- this is a definition of a character device -->
>>>>>           <source mode='bind' service='1234'/>
>>>>>           <source mode='connect' host='1.2.3.4' service='1234'/>
>>>>>           <!-- or other valid character device configuration -->
>>>>
>>
>>>> Do we really want two <source> in a single <backend> in the example, or
>>>> would it be easier to show multiple <rng> devices, one for each type of
>>>> backend?
>>>
>>> That actually is valid for the character device backends. The UDP
>>> backend has to use two separate sources for bi-directional
>>> communication. The definition of that source type is declared as a type
>>> in our RNG schema an I merely reused that.
>>
>> Oh, I didn't realize that.  Do we want to ENFORCE that there are two
>> <source> elements present then?  Or can we always provide a sane default
>> when the user provides only 0 or 1 source?  Depending on that answer, it
>> might be worth additional documentation on why two <source> elements are
>> present, as well as mentioning that order is significant in how they are
>> listed.
>>
> I reused the code to facilitate the operations done with character
> devices. There's present infrastructure [1] that allows to parse, format
> and create commandlines for qemu. The defaults for the syntax of the XML
> and the expected values should be documented in the section describing
> character devices. (But I did not really check if the description is
> exhaustive)
>
> In hindsight I should have linked that section in the description of the
> egd backend model explicitly rather than by just mentioning it.

I actually did that:

backend type='egd'   (Hm there's a mistake here - s/type/model/, I'll 
fix that)

This backend connects to a source using the EGD protocol. The source is 
specified as a character device. Refer to character device host 
interface for more information.

(where "character device host interface" links to :
http://libvirt.org/formatdomain.html#elementsCharHostInterface )

>
> Peter
>
>
> [1]: virDomainChrSourceDefParseXML, virDomainChrSourceDefFormat,
> qemuBuildChrChardevStr
>
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