nvme_get_feature_length2 - Man Page
Retreive the command payload length for a specific feature identifier
int nvme_get_feature_length2 (int fid , __u32 cdw11 , enum nvme_data_tfr dir , __u32 *len );
Feature identifier, see enum nvme_features_id.
The cdw11 value may affect the transfer (only known fid is NVME_FEAT_FID_HOST_ID)
Data transfer direction: false - host to controller, true - controller to host may affect the transfer (only known fid is NVME_FEAT_FID_HOST_MEM_BUF).
On success, set to this features payload length in bytes.
0 on success, -1 with errno set to EINVAL if the function did not recognize fid.
April 2023 libnvme API manual