u32_t sys_arch_mbox_tryfetch(sys_mbox_t *mbox, void **msg) {
if (!trydown(&mbox->read_sem))
return SYS_MBOX_EMPTY;
do_mbox_fetch(mbox, msg);
return 0;
}
/*
* Gets a free TX request for copying data to backend
*/
static inline struct netif_tx_request *netfront_get_page(struct netfront_dev *dev)
{
struct netif_tx_request *tx;
unsigned short id;
struct net_txbuffer* buf;
int flags;
local_irq_save(flags);
if (unlikely(!trydown(&dev->tx_sem))) {
local_irq_restore(flags);
return NULL; /* we run out of available pages */
}
id = get_id_from_freelist(dev->tx_freelist);
buf = &dev->tx_buffers[id];
local_irq_restore(flags);
tx = RING_GET_REQUEST(&dev->tx, dev->tx.req_prod_pvt++);
tx->offset = 0;
tx->size = 0;
tx->id = id;
tx->flags = 0;
#ifdef CONFIG_NETFRONT_PERSISTENT_GRANTS
tx->gref = buf->gref;
#else
tx->gref = buf->gref = GRANT_INVALID_REF;
#endif
#ifdef HAVE_LWIP
buf->pbuf = NULL;
#endif
return tx;
}
/* Try to post the "msg" to the mailbox. */
err_t sys_mbox_trypost(sys_mbox_t *mbox, void *msg)
{
if (!trydown(&mbox->write_sem))
return ERR_MEM;
do_mbox_post(mbox, msg);
return ERR_OK;
}