Commit 296ec009 authored by Michael Wang's avatar Michael Wang Committed by Doug Ledford
Browse files

IB/Verbs: Improve docs for rdma-helpers



Increase the level of documentation for the rdma_cap_* helpers
introduced by Michael Wang <yun.wang@profitbricks.com>.

This patch is loosely based on a patch Michael wrote to enhance the
documentation of these functions, but has been significantly modified
in terms of verbiage.  In addition, the comments were moved from a kernel
Documentation/infiniband/ file to being inline in the header file itself
for the functions in question.  Finally, the documentation was formated
in proper kdoc format.
Signed-off-by: default avatarMichael Wang <yun.wang@profitbricks.com>
Signed-off-by: default avatarDoug Ledford <dledford@redhat.com>
parent 227128fc
......@@ -1775,14 +1775,16 @@ static inline bool rdma_ib_or_iboe(struct ib_device *device, u8 port_num)
}
/**
* rdma_cap_ib_mad - Check if the port of device has the capability Infiniband
* rdma_cap_ib_mad - Check if the port of a device supports Infiniband
* Management Datagrams.
* @device: Device to check
* @port_num: Port number to check
*
* @device: Device to be checked
* @port_num: Port number of the device
* Management Datagrams (MAD) are a required part of the InfiniBand
* specification and are supported on all InfiniBand devices. A slightly
* extended version are also supported on OPA interfaces.
*
* Return false when port of the device don't support Infiniband
* Management Datagrams.
* Return: true if the port supports sending/receiving of MAD packets.
*/
static inline bool rdma_cap_ib_mad(struct ib_device *device, u8 port_num)
{
......@@ -1790,14 +1792,24 @@ static inline bool rdma_cap_ib_mad(struct ib_device *device, u8 port_num)
}
/**
* rdma_cap_ib_smi - Check if the port of device has the capability Infiniband
* Subnet Management Interface.
* rdma_cap_ib_smi - Check if the port of a device provides an Infiniband
* Subnet Management Agent (SMA) on the Subnet Management Interface (SMI).
* @device: Device to check
* @port_num: Port number to check
*
* @device: Device to be checked
* @port_num: Port number of the device
* Each InfiniBand node is required to provide a Subnet Management Agent
* that the subnet manager can access. Prior to the fabric being fully
* configured by the subnet manager, the SMA is accessed via a well known
* interface called the Subnet Management Interface (SMI). This interface
* uses directed route packets to communicate with the SM to get around the
* chicken and egg problem of the SM needing to know what's on the fabric
* in order to configure the fabric, and needing to configure the fabric in
* order to send packets to the devices on the fabric. These directed
* route packets do not need the fabric fully configured in order to reach
* their destination. The SMI is the only method allowed to send
* directed route packets on an InfiniBand fabric.
*
* Return false when port of the device don't support Infiniband
* Subnet Management Interface.
* Return: true if the port provides an SMI.
*/
static inline bool rdma_cap_ib_smi(struct ib_device *device, u8 port_num)
{
......@@ -1807,12 +1819,17 @@ static inline bool rdma_cap_ib_smi(struct ib_device *device, u8 port_num)
/**
* rdma_cap_ib_cm - Check if the port of device has the capability Infiniband
* Communication Manager.
* @device: Device to check
* @port_num: Port number to check
*
* @device: Device to be checked
* @port_num: Port number of the device
* The InfiniBand Communication Manager is one of many pre-defined General
* Service Agents (GSA) that are accessed via the General Service
* Interface (GSI). It's role is to facilitate establishment of connections
* between nodes as well as other management related tasks for established
* connections.
*
* Return false when port of the device don't support Infiniband
* Communication Manager.
* Return: true if the port supports an IB CM (this does not guarantee that
* a CM is actually running however).
*/
static inline bool rdma_cap_ib_cm(struct ib_device *device, u8 port_num)
{
......@@ -1822,12 +1839,14 @@ static inline bool rdma_cap_ib_cm(struct ib_device *device, u8 port_num)
/**
* rdma_cap_iw_cm - Check if the port of device has the capability IWARP
* Communication Manager.
* @device: Device to check
* @port_num: Port number to check
*
* @device: Device to be checked
* @port_num: Port number of the device
* Similar to above, but specific to iWARP connections which have a different
* managment protocol than InfiniBand.
*
* Return false when port of the device don't support IWARP
* Communication Manager.
* Return: true if the port supports an iWARP CM (this does not guarantee that
* a CM is actually running however).
*/
static inline bool rdma_cap_iw_cm(struct ib_device *device, u8 port_num)
{
......@@ -1837,12 +1856,17 @@ static inline bool rdma_cap_iw_cm(struct ib_device *device, u8 port_num)
/**
* rdma_cap_ib_sa - Check if the port of device has the capability Infiniband
* Subnet Administration.
* @device: Device to check
* @port_num: Port number to check
*
* @device: Device to be checked
* @port_num: Port number of the device
* An InfiniBand Subnet Administration (SA) service is a pre-defined General
* Service Agent (GSA) provided by the Subnet Manager (SM). On InfiniBand
* fabrics, devices should resolve routes to other hosts by contacting the
* SA to query the proper route.
*
* Return false when port of the device don't support Infiniband
* Subnet Administration.
* Return: true if the port should act as a client to the fabric Subnet
* Administration interface. This does not imply that the SA service is
* running locally.
*/
static inline bool rdma_cap_ib_sa(struct ib_device *device, u8 port_num)
{
......@@ -1852,12 +1876,19 @@ static inline bool rdma_cap_ib_sa(struct ib_device *device, u8 port_num)
/**
* rdma_cap_ib_mcast - Check if the port of device has the capability Infiniband
* Multicast.
* @device: Device to check
* @port_num: Port number to check
*
* @device: Device to be checked
* @port_num: Port number of the device
* InfiniBand multicast registration is more complex than normal IPv4 or
* IPv6 multicast registration. Each Host Channel Adapter must register
* with the Subnet Manager when it wishes to join a multicast group. It
* should do so only once regardless of how many queue pairs it subscribes
* to this group. And it should leave the group only after all queue pairs
* attached to the group have been detached.
*
* Return false when port of the device don't support Infiniband
* Multicast.
* Return: true if the port must undertake the additional adminstrative
* overhead of registering/unregistering with the SM and tracking of the
* total number of queue pairs attached to the multicast group.
*/
static inline bool rdma_cap_ib_mcast(struct ib_device *device, u8 port_num)
{
......@@ -1867,12 +1898,15 @@ static inline bool rdma_cap_ib_mcast(struct ib_device *device, u8 port_num)
/**
* rdma_cap_af_ib - Check if the port of device has the capability
* Native Infiniband Address.
* @device: Device to check
* @port_num: Port number to check
*
* @device: Device to be checked
* @port_num: Port number of the device
* InfiniBand addressing uses a port's GUID + Subnet Prefix to make a default
* GID. RoCE uses a different mechanism, but still generates a GID via
* a prescribed mechanism and port specific data.
*
* Return false when port of the device don't support
* Native Infiniband Address.
* Return: true if the port uses a GID address to identify devices on the
* network.
*/
static inline bool rdma_cap_af_ib(struct ib_device *device, u8 port_num)
{
......@@ -1881,13 +1915,19 @@ static inline bool rdma_cap_af_ib(struct ib_device *device, u8 port_num)
/**
* rdma_cap_eth_ah - Check if the port of device has the capability
* Ethernet Address Handler.
* Ethernet Address Handle.
* @device: Device to check
* @port_num: Port number to check
*
* @device: Device to be checked
* @port_num: Port number of the device
* RoCE is InfiniBand over Ethernet, and it uses a well defined technique
* to fabricate GIDs over Ethernet/IP specific addresses native to the
* port. Normally, packet headers are generated by the sending host
* adapter, but when sending connectionless datagrams, we must manually
* inject the proper headers for the fabric we are communicating over.
*
* Return false when port of the device don't support
* Ethernet Address Handler.
* Return: true if we are running as a RoCE port and must force the
* addition of a Global Route Header built from our Ethernet Address
* Handle into our header list for connectionless packets.
*/
static inline bool rdma_cap_eth_ah(struct ib_device *device, u8 port_num)
{
......@@ -1897,12 +1937,24 @@ static inline bool rdma_cap_eth_ah(struct ib_device *device, u8 port_num)
/**
* rdma_cap_read_multi_sge - Check if the port of device has the capability
* RDMA Read Multiple Scatter-Gather Entries.
* @device: Device to check
* @port_num: Port number to check
*
* @device: Device to be checked
* @port_num: Port number of the device
* iWARP has a restriction that RDMA READ requests may only have a single
* Scatter/Gather Entry (SGE) in the work request.
*
* Return false when port of the device don't support
* RDMA Read Multiple Scatter-Gather Entries.
* NOTE: although the linux kernel currently assumes all devices are either
* single SGE RDMA READ devices or identical SGE maximums for RDMA READs and
* WRITEs, according to Tom Talpey, this is not accurate. There are some
* devices out there that support more than a single SGE on RDMA READ
* requests, but do not support the same number of SGEs as they do on
* RDMA WRITE requests. The linux kernel would need rearchitecting to
* support these imbalanced READ/WRITE SGEs allowed devices. So, for now,
* suffice with either the device supports the same READ/WRITE SGEs, or
* it only gets one READ sge.
*
* Return: true for any device that allows more than one SGE in RDMA READ
* requests.
*/
static inline bool rdma_cap_read_multi_sge(struct ib_device *device,
u8 port_num)
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment