Re: [PATCH v11 04/17]Add a function make external buffer owner to query capability.

[Ben Hutchings]

On Sat, 2010-09-25 at 12:27 +0800, xiaohui@intel.com wrote:
[...]
 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;
 + }
[...]

Is it really necessary to have a default?

Also have you considered an API for changing the header/data split?

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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[PATCH v11 04/17]Add a function make external buffer owner to query capability.

[xiaohui . xin]

From: Xin Xiaohui xiaohui@intel.com

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

---
 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_tnapi_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
-- 
1.7.3

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