[PATCH] eal/interrupts: Allow UIO interrupts when using igb_uio

[Stephen Hemminger]

On Tue, 4 Jul 2023 20:19:05 +0200
Vladimir Ratnikov <vratnikov at netgate.com> wrote:

> On systems with I225 interfaces it works in interrupt mode(rx), so not only
> LSE interrupts are supported.
> I could try add  rte_intr_cap_single functionality and recheck it twice(if
> several interfaces works in rx_mode=interrupt)
> But actually it worked with changes above(CPU utilization close to the
> zero, data passes through the interface etc)
> 

But this will cause mess with other devices.
For example igb has code that does:

        /* check and configure queue intr-vector mapping */                                          
        if ((rte_intr_cap_multiple(intr_handle) ||                                                   
             !RTE_ETH_DEV_SRIOV(dev).active) &&                                                      
            dev->data->dev_conf.intr_conf.rxq != 0) {                                                
                intr_vector = dev->data->nb_rx_queues;                                               
                if (rte_intr_efd_enable(intr_handle, intr_vector))                                   
                        return -1;                                                                   
        }                                                                                            
                                                                                                     
        /* Allocate the vector list */                                                               
        if (rte_intr_dp_is_en(intr_handle)) {                                                        
                if (rte_intr_vec_list_alloc(intr_handle, "intr_vec",                                 
                                                   dev->data->nb_rx_queues)) {                       
                        PMD_INIT_LOG(ERR, "Failed to allocate %d rx_queues"                          
                                     " intr_vec", dev->data->nb_rx_queues);                          
                        return -ENOMEM;                                                              
                }                                                                                    
        }                                                                                            
                                                                                                     
        /* configure MSI-X for Rx interrupt */                                                       
        eth_igb_configure_msix_intr(dev);   

MSI-X won't work with igb_uio because the interrupt vector region is not shared with userspace.