This document contains some hints to test the function of the VCHIQ driverwithout having additional hardware to the Raspberry Pi. * Requirements & limitations Testing the VCHIQ driver requires a Raspberry Pi with one of the following SoC:  - BCM2835 ( e.g. Raspberry Pi Zero W )  - BCM2836 ( e.g. Raspberry Pi 2 )  - BCM2837 ( e.g. Raspberry Pi 3 B+ ) The BCM2711 used in the Raspberry Pi 4 is currently not supported in themainline kernel. There are no specific requirements to the VideoCore firmware to get VCHIQworking. The test scenarios described in this document based on the tool vchiq_test.Its source code is available here: https://github.com/raspberrypi/userland * Configuration Here are the most common kernel configurations:  1. BCM2835 target SoC (ARM 32 bit)     Just use bcm2835_defconfig which already has VCHIQ enabled.  2. BCM2836/7 target SoC (ARM 32 bit)     Use the multi_v7_defconfig as a base and then enable all VCHIQ options.  3. BCM2837 target SoC (ARM 64 bit)     Use the defconfig which has most of the VCHIQ options enabled. * Scenarios  * Initial test    Check the driver is probed and /dev/vchiq is created  * Functional test    Command: vchiq_test -f 10    Expected output:   Functional test - iters:10   ======== iteration 1 ========   Testing bulk transfer for alignment.   Testing bulk transfer at PAGE_SIZE.   ...  * Ping test    Command: vchiq_test -p    Expected output:   Ping test - service:echo, iters:1000, version 3   vchi ping (size 0) -> 57.000000us   vchi ping (size 0, 0 async, 0 oneway) -> 122.000000us   vchi bulk (size 0, 0 async, 0 oneway) -> 546.000000us   vchi bulk (size 0, 0 oneway) -> 230.000000us   vchi ping (size 0) -> 49.000000us   vchi ping (size 0, 0 async, 0 oneway) -> 70.000000us   vchi bulk (size 0, 0 async, 0 oneway) -> 296.000000us   vchi bulk (size 0, 0 oneway) -> 266.000000us   vchi ping (size 0, 1 async, 0 oneway) -> 65.000000us   vchi bulk (size 0, 0 oneway) -> 456.000000us   vchi ping (size 0, 2 async, 0 oneway) -> 74.000000us   vchi bulk (size 0, 0 oneway) -> 640.000000us   vchi ping (size 0, 10 async, 0 oneway) -> 125.000000us   vchi bulk (size 0, 0 oneway) -> 2309.000000us   vchi ping (size 0, 0 async, 1 oneway) -> 70.000000us   vchi ping (size 0, 0 async, 2 oneway) -> 76.000000us   vchi ping (size 0, 0 async, 10 oneway) -> 105.000000us   vchi ping (size 0, 10 async, 10 oneway) -> 165.000000us   vchi ping (size 0, 100 async, 0 oneway) -> nanus   vchi bulk (size 0, 0 oneway) -> nanus   vchi ping (size 0, 0 async, 100 oneway) -> nanus   vchi ping (size 0, 100 async, 100 oneway) -> infus   vchi ping (size 0, 200 async, 0 oneway) -> infus   ...  * Debugfs test    Command: cat /sys/kernel/debug/vchiq/state    Example output:   State 0: CONNECTED     tx_pos=0x1e8(@43b0acda), rx_pos=0x170(@05493af8)     Version: 8 (min 3)     Stats: ctrl_tx_count=7, ctrl_rx_count=7, error_count=0     Slots: 30 available (29 data), 0 recyclable, 0 stalls (0 data)     Platform: 2835 (VC master)     Local: slots 34-64 tx_pos=0x1e8 recycle=0x1f       Slots claimed:       DEBUG: SLOT_HANDLER_COUNT = 20(0x14)       DEBUG: SLOT_HANDLER_LINE = 1937(0x791)       DEBUG: PARSE_LINE = 1864(0x748)       DEBUG: PARSE_HEADER = -249155224(0xf1263168)       DEBUG: PARSE_MSGID = 67362817(0x403e001)       DEBUG: AWAIT_COMPLETION_LINE = 0(0x0)       DEBUG: DEQUEUE_MESSAGE_LINE = 0(0x0)       DEBUG: SERVICE_CALLBACK_LINE = 0(0x0)       DEBUG: MSG_QUEUE_FULL_COUNT = 0(0x0)       DEBUG: COMPLETION_QUEUE_FULL_COUNT = 0(0x0)     Remote: slots 2-32 tx_pos=0x170 recycle=0x1f       Slots claimed:         2: 10/9       DEBUG: SLOT_HANDLER_COUNT = 20(0x14)       DEBUG: SLOT_HANDLER_LINE = 1851(0x73b)       DEBUG: PARSE_LINE = 1827(0x723)       DEBUG: PARSE_HEADER = -150330912(0xf70a21e0)       DEBUG: PARSE_MSGID = 67113022(0x400103e)       DEBUG: AWAIT_COMPLETION_LINE = 0(0x0)       DEBUG: DEQUEUE_MESSAGE_LINE = 0(0x0)       DEBUG: SERVICE_CALLBACK_LINE = 0(0x0)       DEBUG: MSG_QUEUE_FULL_COUNT = 0(0x0)       DEBUG: COMPLETION_QUEUE_FULL_COUNT = 0(0x0)   Service 0: LISTENING (ref 1) 'PEEK little-endian (0x4b454550)' remote n/a (msg use 0/3840, slot use 0/15)     Bulk: tx_pending=0 (size 0), rx_pending=0 (size 0)     Ctrl: tx_count=0, tx_bytes=0, rx_count=0, rx_bytes=0     Bulk: tx_count=0, tx_bytes=0, rx_count=0, rx_bytes=0     0 quota stalls, 0 slot stalls, 0 bulk stalls, 0 aborted, 0 errors     instance b511f60b