[need help] passthrough does not support polled IO

[gaowayne]

Please acknowledge the following before creating a ticket

• [Yes] I have read the GitHub issues section of REPORTING-BUGS.

Description of the bug: why passthrough does not support polled IO. I have another code working fine with this example https://github.com/axboe/liburing/issues/1418

Environment:

root@salab-hpedl380g11-03:~/wayne/iouring/fio/t# uname -a
Linux salab-hpedl380g11-03 6.8.0-59-generic #61-Ubuntu SMP PREEMPT_DYNAMIC Fri Apr 11 23:16:11 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
root@salab-hpedl380g11-03:~/wayne/iouring/fio/t# 

fio version: latest version Reproduction steps

root@salab-hpedl380g11-03:~/wayne/iouring/fio/t# ./io_uring  -d 4096 -s 128 -c 128 -b 4096 -p 1 -B 1 -F 1 -n 4 -O 0 -r 360 -R 1 -u 1 -- /dev/ng2n1
submitter=0, tid=2851613, file=/dev/ng2n1, nfiles=1, node=-1
submitter=2, tid=2851615, file=/dev/ng2n1, nfiles=1, node=-1
submitter=3, tid=2851616, file=/dev/ng2n1, nfiles=1, node=-1
submitter=1, tid=2851614, file=/dev/ng2n1, nfiles=1, node=-1
polled=1, fixedbufs=1, register_files=1, buffered=1, QD=4096
Engine=io_uring, sq_ring=4096, cq_ring=4096
io: unexpected ret=-22
passthrough doesn't support polled IO
io: unexpected ret=-22
passthrough doesn't support polled IO
io: unexpected ret=-22
passthrough doesn't support polled IO
io: unexpected ret=-22
passthrough doesn't support polled IO