lwIP 2.2.0 Lightweight IP stack

Zero-copy RX

The following code is an example for zero-copy RX ethernet driver:

typedef struct my_custom_pbuf
{
struct pbuf_custom p;
void* dma_descriptor;
} my_custom_pbuf_t;
LWIP_MEMPOOL_DECLARE(RX_POOL, 10, sizeof(my_custom_pbuf_t), "Zero-copy RX PBUF pool");
void my_pbuf_free_custom(void* p)
{
SYS_ARCH_DECL_PROTECT(old_level);
my_custom_pbuf_t* my_puf = (my_custom_pbuf_t*)p;
// invalidate data cache here - lwIP and/or application may have written into buffer!
// (invalidate is faster than flushing, and no one needs the correct data in the buffer)
invalidate_cpu_cache(p->payload, p->tot_len);
SYS_ARCH_PROTECT(old_level);
free_rx_dma_descriptor(my_pbuf->dma_descriptor);
LWIP_MEMPOOL_FREE(RX_POOL, my_pbuf);
SYS_ARCH_UNPROTECT(old_level);
}
void eth_rx_irq()
{
dma_descriptor* dma_desc = get_RX_DMA_descriptor_from_ethernet();
my_custom_pbuf_t* my_pbuf = (my_custom_pbuf_t*)LWIP_MEMPOOL_ALLOC(RX_POOL);
my_pbuf->p.custom_free_function = my_pbuf_free_custom;
my_pbuf->dma_descriptor = dma_desc;
invalidate_cpu_cache(dma_desc->rx_data, dma_desc->rx_length);
struct pbuf* p = pbuf_alloced_custom(PBUF_RAW,
dma_desc->rx_length,
PBUF_REF,
&my_pbuf->p,
dma_desc->rx_data,
dma_desc->max_buffer_size);
if(netif->input(p, netif) != ERR_OK) {
pbuf_free(p);
}
}