net: add qemu_{configure,create}_nic_device(), qemu_find_nic_info()

Most code which directly accesses nd_table[] and nb_nics uses them for
one of two things. Either "I have created a NIC device and I'd like a
configuration for it", or "I will create a NIC device *if* there is a
configuration for it".  With some variants on the theme around whether
they actually *check* if the model specified in the configuration is
the right one.

Provide functions which perform both of those, allowing platforms to
be a little more consistent and as a step towards making nd_table[]
and nb_nics private to the net code.

One might argue that platforms ought to be consistent about whether
they create the unconfigured devices or not, but making significant
user-visible changes is explicitly *not* the intent right now.

The new functions leave the 'model' field of the NICInfo as NULL after
using it for the default NIC model, unlike the qemu_check_nic_model()
function which does set nd->model to match default_model explicitly.
This is acceptable because there is no code which consumes nd->model
except this NIC-matching code in net/net.c, and no reasonable excuse
for any code wanting to use nd->model in future.

Also export the qemu_find_nic_info() helper, as some platforms have
special cases they need to handle.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/include/net/net.h b/include/net/net.h
index ffbd2c8d56..dff1872b4d 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -207,7 +207,47 @@ int qemu_show_nic_models(const char *arg, const char *const *models);
 void qemu_check_nic_model(NICInfo *nd, const char *model);
 int qemu_find_nic_model(NICInfo *nd, const char * const *models,
                         const char *default_model);
+/**
+ * qemu_find_nic_info: Obtain NIC configuration information
+ * @typename: Name of device object type
+ * @match_default: Match NIC configurations with no model specified
+ * @alias: Additional model string to match (for user convenience and
+ *         backward compatibility).
+ *
+ * Search for a NIC configuration matching the NIC model constraints.
+ */
+NICInfo *qemu_find_nic_info(const char *typename, bool match_default,
+                            const char *alias);
+/**
+ * qemu_configure_nic_device: Apply NIC configuration to a given device
+ * @dev: Network device to be configured
+ * @match_default: Match NIC configurations with no model specified
+ * @alias: Additional model string to match
+ *
+ * Search for a NIC configuration for the provided device, using the
+ * additionally specified matching constraints. If found, apply the
+ * configuration using qdev_set_nic_properties() and return %true.
+ *
+ * This is used by platform code which creates the device anyway,
+ * regardless of whether there is a configuration for it. This tends
+ * to be platforms which ignore `--nodefaults` and create net devices
+ * anyway, for example because the Ethernet device on that board is
+ * always physically present.
+ */
+bool qemu_configure_nic_device(DeviceState *dev, bool match_default,
+                               const char *alias);
 
+/**
+ * qemu_create_nic_device: Create a NIC device if a configuration exists for it
+ * @typename: Object typename of network device
+ * @match_default: Match NIC configurations with no model specified
+ * @alias: Additional model string to match
+ *
+ * Search for a NIC configuration for the provided device type. If found,
+ * create an object of the corresponding type and return it.
+ */
+DeviceState *qemu_create_nic_device(const char *typename, bool match_default,
+                                    const char *alias);
 void print_net_client(Monitor *mon, NetClientState *nc);
 void net_socket_rs_init(SocketReadState *rs,
                         SocketReadStateFinalize *finalize,