From: Jakub Kicinski Date: Fri, 7 Apr 2023 01:25:30 +0000 (-0700) Subject: docs: net: reformat driver.rst from a list to sections X-Git-Tag: v6.6.17~4755^2~145^2~6 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d2f5c68e3f7157e874a759e382a5eaffa775b869;p=platform%2Fkernel%2Flinux-rpi.git docs: net: reformat driver.rst from a list to sections driver.rst had a historical form of list of common problems. In the age os Sphinx and rendered documentation it's better to use the more usual title + text format. This will allow us to render kdoc into the output more naturally. No changes to the actual text. Signed-off-by: Jakub Kicinski --- diff --git a/Documentation/networking/driver.rst b/Documentation/networking/driver.rst index 64f7236..3040a74 100644 --- a/Documentation/networking/driver.rst +++ b/Documentation/networking/driver.rst @@ -4,15 +4,19 @@ Softnet Driver Issues ===================== -Transmit path guidelines: +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 its - transmit function will become busy. +Stop queues in advance +---------------------- - Instead it must maintain the queue properly. For example, - for a driver implementing scatter-gather this means:: +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 its +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) @@ -42,56 +46,73 @@ Transmit path guidelines: return NETDEV_TX_OK; } - And then at the end of your TX reclamation event handling:: +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:: +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:: +and:: if (TX_BUFFS_AVAIL(dp) == 0) - and:: +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. +No exclusive ownership +---------------------- + +An ndo_start_xmit method must not modify the shared parts of a +cloned SKB. + +Timely completions +------------------ + +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. -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. - 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. - 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 +================== -Probing guidelines: +Address validation +------------------ + +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) 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() +Quiescence +---------- -Close/stop guidelines: +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. -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. +Auto-close +---------- -2) The ndo_stop routine will be called by unregister_netdevice - if device is still UP. +The ndo_stop routine will be called by unregister_netdevice +if device is still UP.