docs: networking: convert driver.txt to ReST

- add SPDX header;
- add a document title;
- mark code blocks and literals as such;
- adjust identation, whitespaces and blank lines;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 0 insertions, 93 deletions

diff --git a/Documentation/networking/driver.txt b/Documentation/networking/driver.txt
deleted file mode 100644
index da59e2884130..000000000000
--- a/Documentation/networking/driver.txt
+++ /dev/null
@@ -1,93 +0,0 @@
-Document about softnet driver issues
-
-Transmit path guidelines:
-
-1) The ndo_start_xmit method must not return NETDEV_TX_BUSY under
-   any normal circumstances.  It is considered a hard error unless
-   there is no way your device can tell ahead of time when it's
-   transmit function will become busy.
-
-   Instead it must maintain the queue properly.  For example,
-   for a driver implementing scatter-gather this means:
-
-	static netdev_tx_t drv_hard_start_xmit(struct sk_buff *skb,
-					       struct net_device *dev)
-	{
-		struct drv *dp = netdev_priv(dev);
-
-		lock_tx(dp);
-		...
-		/* This is a hard error log it. */
-		if (TX_BUFFS_AVAIL(dp) <= (skb_shinfo(skb)->nr_frags + 1)) {
-			netif_stop_queue(dev);
-			unlock_tx(dp);
-			printk(KERN_ERR PFX "%s: BUG! Tx Ring full when queue awake!\n",
-			       dev->name);
-			return NETDEV_TX_BUSY;
-		}
-
-		... queue packet to card ...
-		... update tx consumer index ...
-
-		if (TX_BUFFS_AVAIL(dp) <= (MAX_SKB_FRAGS + 1))
-			netif_stop_queue(dev);
-
-		...
-		unlock_tx(dp);
-		...
-		return NETDEV_TX_OK;
-	}
-
-   And then at the end of your TX reclamation event handling:
-
-	if (netif_queue_stopped(dp->dev) &&
-            TX_BUFFS_AVAIL(dp) > (MAX_SKB_FRAGS + 1))
-		netif_wake_queue(dp->dev);
-
-   For a non-scatter-gather supporting card, the three tests simply become:
-
-		/* This is a hard error log it. */
-		if (TX_BUFFS_AVAIL(dp) <= 0)
-
-   and:
-
-		if (TX_BUFFS_AVAIL(dp) == 0)
-
-   and:
-
-	if (netif_queue_stopped(dp->dev) &&
-            TX_BUFFS_AVAIL(dp) > 0)
-		netif_wake_queue(dp->dev);
-
-2) An ndo_start_xmit method must not modify the shared parts of a
-   cloned SKB.
-
-3) Do not forget that once you return NETDEV_TX_OK from your
-   ndo_start_xmit method, it is your driver's responsibility to free
-   up the SKB and in some finite amount of time.
-
-   For example, this means that it is not allowed for your TX
-   mitigation scheme to let TX packets "hang out" in the TX
-   ring unreclaimed forever if no new TX packets are sent.
-   This error can deadlock sockets waiting for send buffer room
-   to be freed up.
-
-   If you return NETDEV_TX_BUSY from the ndo_start_xmit method, you
-   must not keep any reference to that SKB and you must not attempt
-   to free it up.
-
-Probing guidelines:
-
-1) Any hardware layer address you obtain for your device should
-   be verified.  For example, for ethernet check it with
-   linux/etherdevice.h:is_valid_ether_addr()
-
-Close/stop guidelines:
-
-1) After the ndo_stop routine has been called, the hardware must
-   not receive or transmit any data.  All in flight packets must
-   be aborted. If necessary, poll or wait for completion of 
-   any reset commands.
-
-2) The ndo_stop routine will be called by unregister_netdevice
-   if device is still UP.