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SubjectRe: [RFC 1/2] PCI-Express Non-Transparent Bridge Support
From
Jon,

On Fri, Jul 13, 2012 at 5:44 PM, Jon Mason <jon.mason@intel.com> wrote:

..............
> +/**
> + * ntb_ring_sdb() - Set the doorbell on the secondary/external side
> + * @ndev: pointer to ntb_device instance
> + * @db: doorbell to ring
> + *
> + * This function allows triggering of a doorbell on the secondary/external
> + * side that will initiate an interrupt on the remote host
> + *
> + * RETURNS: An appropriate -ERRNO error value on error, or zero for success.
> + */
> +int ntb_ring_sdb(struct ntb_device *ndev, unsigned int db)
> +{
> + dev_dbg(&ndev->pdev->dev, "%s: ringing doorbell %d\n", __func__, db);
> +

> + if (db >= ndev->max_cbs)
> + return -EINVAL;

How about moving this max_cbs error check in the upper level
callers(example in ntb_process_tx)?
That way you won't have to defer handling some negative cases all the
way till the end.

So ntb_process_tx could now look like:

.....
error=0;
if (entry->len > transport_mtu) {
...
error=1;
}
else if (qp->qp_num >= qp->ndev->max_cbs) {
...
error=1;
}
if (unlikely(error)) {
ntb_list_add_tail(&qp->txc_lock, &entry->entry, &qp->txc);
if (qp->tx_handler)
qp->tx_handler(qp);
return 0;
}
.................
No further comments below

> +
> +static int ntb_process_tx(struct ntb_transport_qp *qp,
> + struct ntb_queue_entry *entry)
> +{
> + struct ntb_payload_header *hdr;
> + void *offset;
> +
> + offset = qp->tx_offset;
> + hdr = offset;
> +
> + pr_debug("%lld - offset %p, tx %p, entry len %d flags %x buff %p\n",
> + qp->tx_pkts, offset, qp->tx_offset, entry->len, entry->flags,
> + entry->buf);
> + if (hdr->flags) {
> + ntb_list_add_head(&qp->txq_lock, &entry->entry, &qp->txq);
> + qp->tx_ring_full++;
> + return -EAGAIN;
> + }
> +
> + if (entry->len > transport_mtu) {
> + pr_err("Trying to send pkt size of %d\n", entry->len);
> + entry->flags = HW_ERROR_FLAG;
> +
> + ntb_list_add_tail(&qp->txc_lock, &entry->entry, &qp->txc);
> +
> + if (qp->tx_handler)
> + qp->tx_handler(qp);
> +
> + return 0;
> + }
> +
> + ntb_tx_copy_task(qp, entry, offset);
> +
> + qp->tx_offset =
> + (qp->tx_offset +
> + ((transport_mtu + sizeof(struct ntb_payload_header)) * 2) >=
> + qp->tx_mw_end) ? qp->tx_mw_begin : qp->tx_offset + transport_mtu +
> + sizeof(struct ntb_payload_header);
> +
> + qp->tx_pkts++;
> +
> + return 0;
> +}
> +


Chetan Loke


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