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Re: [libvirt] anyone implementing host device enumeration?



On Tue, Sep 30, 2008 at 12:17:27AM -0400, David Lively wrote:
> diff --git a/src/internal.h b/src/internal.h
> index d96504d..9a94f6d 100644
> --- a/src/internal.h
> +++ b/src/internal.h
> @@ -292,6 +307,25 @@ struct _virStorageVol {
>  };
>  
>  
> +/**
> + * _virNodeDevice:
> + *
> + * Internal structure associated with a node device
> + */
> +struct _virNodeDevice {
> +    unsigned int magic;                 /* specific value to check */
> +    int refs;                           /* reference count */
> +    virConnectPtr conn;                 /* pointer back to the connection */
> +    char *key;                          /* device key */
> +    char *name;                         /* device name */
> +    char *parent_key;                   /* parent device */
> +    char *bus_name;                     /* (optional) bus name */
> +    xmlNodePtr bus;                     /* (optional) bus descriptor */
> +    char **cap_names;                   /* capability names (null-term) */
> +    xmlNodePtr *caps;                   /* capability descs (null-term) */
> +};

This is not the right way to maintain the internal representation of
devices.

The model we follow is to have 2, sometimes 3 structs to represent
an object. I'll summarize in terms of domain objects

 - virDomainPtr - the public opaque struct representing a domain
                  the internal struct is defined in internal.h
                  and merely contains reference counting, connection
                  pointer, and any unique keys (ID, name, UUID).

 - virDomainObjPtr - the internal struct representing the state of
                     a domain object. Not all drivers use us - only
                     stateful drivers do. It is used to track state
                     such as guest PID, logfile, running state, 
                     and a pointer to the live and inactive configs
                     This is done in domain_conf.h/.c

 - virDomainDefPtr - the internal struct representing the canonical
                     configuration of a domain. This is a direct
                     mapping of the XML into a series of structs.
                     This is done in domain_conf.h/.c


So, in the context for host devices we need a few changes. In the
internal.h file, you should only store the key/name attributes.

There should then be a separate file handling configuration parsing
and formatting, node_device_conf.h/.c.  There is probably no need
for a state object, so skip virNodeDeviceObjPtr, and just create a
virNodeDeviceDefPtr representing the XML format as a series of 
structs/unions, etc. See virDomainDefPtr for a good example. This
should not store any xmlNodePtr instances - it should be all done
as explicit struct/enum fields

The node_device_conf.c file should at mimium have 2 methods, one
for converting an XML document into a virNodeDeviceDefPtr object,
and one for the converting a virNodeDeviceObjPtr back into an XML
document. Follow the existing API naming / method signatures that
are seen in domain_conf.h / network_conf.h for current 'best practice'


Daniel
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