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From: xiaohui.xin on 6 Aug 2010 05:20
From: Xin Xiaohui <xiaohui.xin(a)intel.com>

The external buffer owner can use the functions to get
the capability of the underlying NIC driver.

Signed-off-by: Xin Xiaohui <xiaohui.xin(a)intel.com>
Signed-off-by: Zhao Yu <yzhaonew(a)gmail.com>
Reviewed-by: Jeff Dike <jdike(a)linux.intel.com>

---
include/linux/netdevice.h | 2 +
net/core/dev.c | 49 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 51 insertions(+), 0 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index aba0308..5f192de 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1599,6 +1599,8 @@ extern gro_result_t napi_frags_finish(struct napi_struct *napi,
gro_result_t ret);
extern struct sk_buff * napi_frags_skb(struct napi_struct *napi);
extern gro_result_t napi_gro_frags(struct napi_struct *napi);
+extern int netdev_mp_port_prep(struct net_device *dev,
+ struct mpassthru_port *port);

static inline void napi_free_frags(struct napi_struct *napi)
{
diff --git a/net/core/dev.c b/net/core/dev.c
index 264137f..636f11b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2468,6 +2468,55 @@ void netif_nit_deliver(struct sk_buff *skb)
rcu_read_unlock();
}

+/* To support meidate passthru(zero-copy) with NIC driver,
+ * we'd better query NIC driver for the capability it can
+ * provide, especially for packet split mode, now we only
+ * query for the header size, and the payload a descriptor
+ * may carry. If a driver does not use the API to export,
+ * then we may try to use a default value, currently,
+ * we use the default value from an IGB driver. Now,
+ * it's only called by mpassthru device.
+ */
+#if defined(CONFIG_MEDIATE_PASSTHRU) || defined(CONFIG_MEDIATE_PASSTHRU_MODULE)
+int netdev_mp_port_prep(struct net_device *dev,
+ struct mpassthru_port *port)
+{
+ int rc;
+ int npages, data_len;
+ const struct net_device_ops *ops = dev->netdev_ops;
+
+ if (ops->ndo_mp_port_prep) {
+ rc = ops->ndo_mp_port_prep(dev, port);
+ if (rc)
+ return rc;
+ } else {
+ /* If the NIC driver did not report this,
+ * then we try to use default value.
+ */
+ port->hdr_len = 128;
+ port->data_len = 2048;
+ port->npages = 1;
+ }
+
+ if (port->hdr_len <= 0)
+ goto err;
+
+ npages = port->npages;
+ data_len = port->data_len;
+ if (npages <= 0 || npages > MAX_SKB_FRAGS ||
+ (data_len < PAGE_SIZE * (npages - 1) ||
+ data_len > PAGE_SIZE * npages))
+ goto err;
+
+ return 0;
+err:
+ dev_warn(&dev->dev, "invalid page constructor parameters\n");
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL(netdev_mp_port_prep);
+#endif
+
/**
* netif_receive_skb - process receive buffer from network
* @skb: buffer to process
--
1.5.4.4

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Prev: [RFC PATCH v9 01/16] Add a new structure for skb buffer from external.
Next: [RFC PATCH v9 15/16] An example how to modifiy NIC driver to use napi_gro_frags() interface