[dpdk-dev] management of non-PCI devices

[Thomas Monjalon <thomas.monjalon@6wind.com>]

As noticed when reviewing the changes for hotplugging ring PMD,
	http://dpdk.org/ml/archives/dev/2015-July/021872.html
a driver is considered in ethdev and EAL as a PCI driver:

 * Each Ethernet driver acts as a PCI driver and is represented by a generic
 * *eth_driver* structure that holds:
 * - An *rte_pci_driver* structure (which must be the first field).
 * - The *eth_dev_init* function invoked for each matching PCI device.
 * - The *eth_dev_uninit* function invoked for each matching PCI device.
 * - The size of the private data to allocate for each matching device.
 */
struct eth_driver {                                                                                              
    struct rte_pci_driver pci_drv;    /**< The PMD is also a PCI driver. */
    eth_dev_init_t eth_dev_init;      /**< Device init function. */
    eth_dev_uninit_t eth_dev_uninit;  /**< Device uninit function. */
    unsigned int dev_private_size;    /**< Size of device private data. */
};

So the non PCI drivers don't use rte_eth_driver_register().
Then a difference is made with these flags:
enum pmd_type {
    PMD_VDEV = 0,
    PMD_PDEV = 1,
};

With this kind of weird things:
static struct rte_driver rte_virtio_driver = {
    .type = PMD_PDEV,                                                                                            
    .init = rte_virtio_pmd_init,
};
Because virtio is a virtual device with a virtual PCI address.

All these things are not normal and make EAL code more and more difficult to
maintain. That's why we must stop accepting new code using these workarounds
and start working on a refactoring.

Comments welcome