IONIC_DV_PD_SET_RQCMB(3)   Ionic Programmer's Manual  IONIC_DV_PD_SET_RQCMB(3)

NAME
       ionic_dv_pd_set_rqcmb - Specify receive queue preference for controller
       memory bar

SYNOPSIS
              #include <infiniband/ionic_dv.h>

              int ionic_dv_pd_set_rqcmb(struct ibv_pd *ibpd, bool enable, bool expdb,
                                         bool require);

DESCRIPTION
       ionic_dv_pd_set_rqcmb() configures the controller memory bar (CMB)
       preferences for receive queues created under the protection domain
       ibpd.  Receive queues created after this call will use the CMB
       according to the specified preferences.

       When CMB is enabled, the receive queue ring buffer is placed in device
       memory (the controller memory bar) instead of host memory, which can
       reduce doorbell latency.

       Express doorbell (expdb) is an additional optimization that further
       reduces doorbell overhead when the receive queue is placed in CMB.

       The require flag controls whether creation should fail if the requested
       CMB preferences cannot be met.  When require is false, the driver will
       fall back to host memory if CMB is unavailable.

ARGUMENTS
       ibpd   The protection domain to configure.  Must be an ionic protection
              domain.

       enable Allow the use of the controller memory bar for receive queues.

       expdb  Allow the use of express doorbell optimizations.  Only
              meaningful when enable is true.

       require
              Require that the CMB preferences are met.  If true and the
              preferences cannot be satisfied, queue creation will fail
              instead of falling back to host memory.  Only meaningful when
              enable is true.

RETURN VALUE
       Returns 0 on success, or a positive errno value on failure:

       EPERM  ibpd is not an ionic protection domain.

       EINVAL require is true with expdb true, but the device does not support
              express doorbell for receive queues.

SEE ALSO
       ionicdv(7), ionic_dv_pd_set_sqcmb(3), ionic_dv_pd_set_udma_mask(3)

AUTHORS
       Advanced Micro Devices, Inc.

ionic                             2025-06-23          IONIC_DV_PD_SET_RQCMB(3)