Soft RoCE (RXE) - The software RoCE driver
ib_rxe implements the RDMA transport and registers to the RDMA core
device as a kernel verbs provider. It also implements the packet IO
layer. On the other hand ib_rxe registers to the Linux netdev stack
as a udp encapsulating protocol, in that case RDMA, for sending and
receiving packets over any Ethernet device. This yields a RDMA
transport over the UDP/Ethernet network layer forming a RoCEv2
compatible device.
The configuration procedure of the Soft RoCE drivers requires
binding to any existing Ethernet network device. This is done with
/sys interface.
A userspace Soft RoCE library (librxe) provides user applications
the ability to run with Soft RoCE devices. The use of rxe verbs ins
user space requires the inclusion of librxe as a device specifics
plug-in to libibverbs. librxe is packaged separately.
Architecture:
+-----------------------------------------------------------+
| Application |
+-----------------------------------------------------------+
+-----------------------------------+
| libibverbs |
User +-----------------------------------+
+----------------+ +----------------+
| librxe | | HW RoCE lib |
+----------------+ +----------------+
+---------------------------------------------------------------+
+--------------+ +------------+
| Sockets | | RDMA ULP |
+--------------+ +------------+
+--------------+ +---------------------+
| TCP/IP | | ib_core |
+--------------+ +---------------------+
+------------+ +----------------+
Kernel | ib_rxe | | HW RoCE driver |
+------------+ +----------------+
+------------------------------------+
| NIC driver |
+------------------------------------+
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+-----------------------------------------------------------+
| Application |
+-----------------------------------------------------------+
+-----------------------------------+
| libibverbs |
User +-----------------------------------+
+----------------+ +----------------+
| librxe | | HW RoCE lib |
+----------------+ +----------------+
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+--------------+ +------------+
| Sockets | | RDMA ULP |
+--------------+ +------------+
+--------------+ +---------------------+
| TCP/IP | | ib_core |
+--------------+ +---------------------+
+------------+ +----------------+
Kernel | ib_rxe | | HW RoCE driver |
+------------+ +----------------+
+------------------------------------+
| NIC driver |
+------------------------------------+
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Soft RoCE resources:
[1[ https://github.com/SoftRoCE/librxe-dev librxe - source code in
Github
[2] https://github.com/SoftRoCE/rxe-dev/wiki/rxe-dev:-Home - Soft RoCE
Wiki page
[3] https://github.com/SoftRoCE/librxe-dev - Soft RoCE userspace library
Signed-off-by: Kamal Heib <kamalh@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: Moni Shoua <monis@mellanox.com>
Reviewed-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Added UCMA and CMA support for multicast join flags. Flags are
passed using UCMA CM join command previously reserved fields.
Currently supporting two join flags indicating two different
multicast JoinStates:
1. Full Member:
The initiator creates the Multicast group(MCG) if it wasn't
previously created, can send Multicast messages to the group
and receive messages from the MCG.
2. Send Only Full Member:
The initiator creates the Multicast group(MCG) if it wasn't
previously created, can send Multicast messages to the group
but doesn't receive any messages from the MCG.
IB: Send Only Full Member requires a query of ClassPortInfo
to determine if SM/SA supports this option. If SM/SA
doesn't support Send-Only there will be no join request
sent and an error will be returned.
ETH: When Send Only Full Member is requested no IGMP join
will be sent.
Signed-off-by: Alex Vesker <valex@mellanox.com>
Reviewed by: Hal Rosenstock <hal@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Added a new SA port attribute containing SM ClassPortInfo fields,
(ClassPortInfo fields: Table 126 IB Spec 1.3.). This is useful for
checking SM support for specific features. The attribute is cached
to avoid resending queries, caching is done when a successful
ClassPortInfo reply is received on the port. Invalidation of the
attribute is done on SM change events, SM re-registration events,
and SM LID change events. The fields in ClassPortInfo should not
change during SM runtime without an event.
Signed-off-by: Alex Vesker <valex@mellanox.com>
Reviewed by: Hal Rosenstock <hal@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Fixes an oops that might happen if uverbs_close races with
remove_one.
Both contexts may run ib_uverbs_cleanup_ucontext, it depends
on the flow.
Currently, there is no protection for a case that remove_one
didn't make the cleanup it runs to its end, the underlying
ib_device was freed then uverbs_close will call
ib_uverbs_cleanup_ucontext and OOPs.
Above might happen if uverbs_close deleted the file from the list
then remove_one didn't find it and runs to its end.
Fixes to protect against that case by a new cleanup lock so that
ib_uverbs_cleanup_ucontext will be called always before that
remove_one is ended.
Fixes: 35d4a0b63d ("IB/uverbs: Fix race between ib_uverbs_open and remove_one")
Reported-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
The kfree() function was called in a few cases by the mthca_reset()
function during error handling even if the passed variables "bridge_header"
and "hca_header" contained a null pointer.
Adjust jump targets according to the Linux coding style convention.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
The pci_dev_put() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.
This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
The sc_return_credits() function tests whether its argument is NULL
and then returns immediately. Thus the test around the call is not needed.
This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Expose IB diagnostic hardware counters.
The counters count IB events and are applicable for IB and RoCE.
The counters can be divided into two groups, per device and per port.
Device counters are always exposed.
Port counters are exposed only if the firmware supports per port counters.
rq_num_dup and sq_num_to are only exposed if we have firmware support
for them, if we do, we expose them per device and per port.
rq_num_udsdprd and num_cqovf are device only counters.
rq - denotes responder.
sq - denotes requester.
|-----------------------|---------------------------------------|
| Name | Description |
|-----------------------|---------------------------------------|
|rq_num_lle | Number of local length errors |
|-----------------------|---------------------------------------|
|sq_num_lle | number of local length errors |
|-----------------------|---------------------------------------|
|rq_num_lqpoe | Number of local QP operation errors |
|-----------------------|---------------------------------------|
|sq_num_lqpoe | Number of local QP operation errors |
|-----------------------|---------------------------------------|
|rq_num_lpe | Number of local protection errors |
|-----------------------|---------------------------------------|
|sq_num_lpe | Number of local protection errors |
|-----------------------|---------------------------------------|
|rq_num_wrfe | Number of CQEs with error |
|-----------------------|---------------------------------------|
|sq_num_wrfe | Number of CQEs with error |
|-----------------------|---------------------------------------|
|sq_num_mwbe | Number of Memory Window bind errors |
|-----------------------|---------------------------------------|
|sq_num_bre | Number of bad response errors |
|-----------------------|---------------------------------------|
|sq_num_rire | Number of Remote Invalid request |
| | errors |
|-----------------------|---------------------------------------|
|rq_num_rire | Number of Remote Invalid request |
| | errors |
|-----------------------|---------------------------------------|
|sq_num_rae | Number of remote access errors |
|-----------------------|---------------------------------------|
|rq_num_rae | Number of remote access errors |
|-----------------------|---------------------------------------|
|sq_num_roe | Number of remote operation errors |
|-----------------------|---------------------------------------|
|sq_num_tree | Number of transport retries exceeded |
| | errors |
|-----------------------|---------------------------------------|
|sq_num_rree | Number of RNR NAK retries exceeded |
| | errors |
|-----------------------|---------------------------------------|
|rq_num_rnr | Number of RNR NAKs sent |
|-----------------------|---------------------------------------|
|sq_num_rnr | Number of RNR NAKs received |
|-----------------------|---------------------------------------|
|rq_num_oos | Number of Out of Sequence requests |
| | received |
|-----------------------|---------------------------------------|
|sq_num_oos | Number of Out of Sequence NAKs |
| | received |
|-----------------------|---------------------------------------|
|rq_num_udsdprd | Number of UD packets silently |
| | discarded on the Receive Queue due to |
| | lack of receive descriptor |
|-----------------------|---------------------------------------|
|rq_num_dup | Number of duplicate requests received |
|-----------------------|---------------------------------------|
|sq_num_to | Number of time out received |
|-----------------------|---------------------------------------|
|num_cqovf | Number of CQ overflows |
|-----------------------|---------------------------------------|
Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Add a function to query diagnostics counters from the firmware.
Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Add a bit that indicates if the firmware supports per port
diagnostic counters.
Signed-off-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Portmapper messages are short and do not occupy more than 512 bytes.
Lower portmapper message size to 512 bytes. This change significantly
reduces the amount of memory needed when trying to establish a large
number of connections simultaneously. The old value is based on page
size.
Signed-off-by: Faisal Latif <faisal.latif@intel.com>
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Decouple SG support from HW ability to do UD checksum.
This coupling is for historical reasons and removed with 'commit
ec5f061564 ("net: Kill link between CSUM and SG features.")'
During driver load it is assumed that device does not supports SG. The
final decision is taken after creating UD QP based on device capability.
Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
We allocate a small tracking structure as part of mlx4_ib_resize_cq().
However, we don't need to use GFP_ATOMIC -- immediately after the
allocation, we call mlx4_cq_resize(), which allocates a command
mailbox with GFP_KERNEL and then sleeps on a firmware command, so we
better not be in an atomic context.
This actually has a real impact, because when this GFP_ATOMIC
allocation fails (and GFP_ATOMIC does fail in practice) then a
userspace consumer resizing a CQ will get a spurious failure that we
can easily avoid.
Signed-off-by: Roland Dreier <roland@purestorage.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
There is a strict policy in the Linux kernel that new drivers must be
disabled by default. Hence leave out the "default m" line from Kconfig.
Fixes: f48ad614c1 ("IB/hfi1: Move driver out of staging")
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Jubin John <jubin.john@intel.com>
Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: <stable@vger.kernel.org> # v4.7+
Acked-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
There is a strict policy in the Linux kernel that new drivers must be
disabled by default. Hence leave out the "default m" line from Kconfig.
Fixes: 0194621b22 ("IB/rdmavt: Create module framework and handle driver registration")
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Jubin John <jubin.john@intel.com>
Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: <stable@vger.kernel.org> # v4.6+
Signed-off-by: Doug Ledford <dledford@redhat.com>
The q-counter-id is given in modify-QP command associates
the QP with the counter. The offset to which the counter
ID was set is incorrect, causing IB port counters not to
count on QP.
Fixes: 0837e86a7a ('IB/mlx5: Add per port counters')
Signed-off-by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Tested-by: Mark Bloch <markb@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Number of outstanding_pi may overflow and as a result may indicate that
there are no elements in the queue. The effect of doing this is that the
MAD layer will get stuck waiting for completions. The MAD layer will
think that the QP is full - because it didn't receive these completions.
This fix changes it so the outstanding_pi number is increased
with 32-bit wraparound and is not limited to max_send_wr so
that the difference between outstanding_pi and outstanding_ci will
really indicate the number of outstanding completions.
Cc: Stable <stable@vger.kernel.org>
Fixes: ea6dc20362 ('IB/mlx5: Reorder GSI completions')
Signed-off-by: Slava Shwartsman <slavash@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Reviewed-by: Haggai Eran <haggaie@mellanox.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Doug Ledford <dledford@redhat.com>
i40iw_puda_get_listbuf may return NULL if the list is empty.
Add NULL check prior to accessing the pointer.
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Change dup_ack_thressh to u8 since it is a 3 bit field.
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
In i40iw_cq_poll_completion, we always move the tail. So there is
no reason to check for overflow everytime we move the head.
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Replace a subtract and multiply with an add; while populating fragments
in SQ wqe.
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Child_listen_node pointer is used in a debug print after kfree.
Move the print before kfree.
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Fix size parameter passed to i40iw_reg_phys_mr and use it to
register memory.
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Remove the complicated logic to free the iw_cm_id inside iw_cm
event handlers vs when an application thread destroys the cm_id.
Also remove the block in iw_destroy_cm_id() to block the application
until all references are removed. This block can cause a deadlock when
disconnecting or destroying cm_ids inside an rdma_cm event handler.
Simply allowing the last deref of the iw_cm_id to free the memory
is cleaner and avoids this potential deadlock. Also a flag is added,
IW_CM_DROP_EVENTS, that is set when the cm_id is marked for destruction.
If any events are pending on this iw_cm_id, then as they are processed
they will be dropped vs posted upstream if IW_CM_DROP_EVENTS is set.
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Blocking in c4iw_destroy_qp() causes a deadlock when apps destroy a qp
or disconnect a cm_id from their cm event handler function. There is
no need to block here anyway, so just replace the refcnt atomic with a
kref object and free the memory on the last put.
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Doug Ledford <dledford@redhat.com>
This forces the connection to abort if the application failed to
disconnect before flushing. This is aligned with how the common
flush services work.
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
There exists a race where the application can setup a connection
and then disconnect it before iw_cxgb4 processes the fw4_ack
message. For passive side connections, the fw4_ack message is
used to know when to stop the ep timer for MPA_REPLY messages.
If the application disconnects before the fw4_ack is handled then
c4iw_ep_disconnect() needs to clean up the timer state and stop the
timer before restarting it for the disconnect timer. Failure to do this
results in a "timer already started" message and a premature stopping
of the disconnect timer.
Fixes: e4b76a2 ("RDMA/iw_cxgb4: stop_ep_timer() after MPA negotiation")
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
During connection establishment with a large number of
connections, it is possible that the connection requests
might fail. Adding flow control prevents this failure.
Change ibnl_unicast to use blocking to enable flow control.
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Faisal Latif <faisal.latif@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Elsewhere the sin_family field holds a value with a name of the form
AF_..., so it seems reasonable to do so here as well. Also the values
of PF_INET and AF_INET are the same.
The Coccinelle semantic patch that makes this change is as follows:
// <smpl>
@@
struct sockaddr_in sip;
@@
(
sip.sin_family ==
- PF_INET
+ AF_INET
|
sip.sin_family !=
- PF_INET
+ AF_INET
|
sip.sin_family =
- PF_INET
+ AF_INET
)
// </smpl>
Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
The commit 0f8ab0b6e9 ("RDMA/iw_cxgb4: Low resource fixes for Memory
registration") from Jun 10, 2016, leads to the following static checker
warning:
drivers/infiniband/hw/cxgb4/mem.c:612 c4iw_alloc_mw()
error: use kfree_skb() here instead of kfree(mhp->dereg_skb)
Also fixes skb leak in c4iw_dealloc_mw
Fixes: 0f8ab0b6e9 ("RDMA/iw_cxgb4: Low resource fixes for Memory registration")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Export the firmware version through the core.
Acked-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Now that all the devices have stopped exporting their own sysfs
entry points we can have the core export this on their behalf.
Eventually this may be removed but this provides for backwards
compatibility.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Using this allows for devices to specify the format of their
firmware version rather than forcing a format.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
And remove sysfs file in favor of the common core.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
And remove sysfs in favor of the core support.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
And remove the sysfs in favor of the core version.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
And remove the sysfs entry in favor of the core support.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
And remove sysfs entry in favor of the common code.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
And remove the sysfs in favor of common core version.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
And remove sysfs support in favor of the core version.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
And remove sysfs fw_ver in favor of the core.
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Also remove fw_ver sysfs to be replaced by the common core one.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Allow for a common core function to get firmware version strings
from the individual devices.
In later patches this format can then then be used to pass a
properly formated version string through the IPoIB layer.
The problem with the current code in the IPoIB layer is that it is
specific to certain hardware types.
Furthermore, this gives us a common function through which the core
can provide a common sysfs entry. Eventually we may want to
remove the sysfs export but this provides for user space backwards
compatibility.
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
