Car display shows unreadable device (Volvo v70 2015)

[andersthomson]

Hi,

I've a volvo v70 which supports 'ipod' as a USB source (alongside USB mass storage). I've sccessfully compiled the kernel module and idod application on my OrangePi Zero (which has otherwise served as a mass storage dev gadget, so I know the gadget support works ok).

However, upon starting the iod application, nothing is logged. As best I can tell from the application log, the car never sends any USB command to the gadget/application.

The kernel log however shows a few interactions which might suggest what's going on. Using commit 731a471 I find:

[ 253.439735] g_ipod_audio: loading out-of-tree module taints kernel.
[ 253.440169] g_ipod_audio: module verification failed: signature and/or required key missing - tainting kernel

[ 253.440891] **********************************************************
[ 253.440899] ** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **
[ 253.440906] ** **
[ 253.440913] ** trace_printk() being used. Allocating extra memory. **
[ 253.441040] ** **
[ 253.441073] ** This means that this is a DEBUG kernel and it is **
[ 253.441092] ** unsafe for production use. **
[ 253.441114] ** **
[ 253.441135] ** If you see this message and you are not debugging **
[ 253.441170] ** the kernel, report this immediately to your vendor! **
[ 253.441183] ** **
[ 253.441189] ** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE **
[ 253.441196] **********************************************************
[ 253.489859] ipod-gadget: init
[ 253.489912] g_ipod gadget: = ipod_bind()
[ 253.526046] Mass Storage Function, version: 2009/09/11
[ 253.526077] LUN: removable file: (no medium)
[ 253.526104] g_ipod gadget: = ipod_config_ptp_bind()
[ 253.526379] ipod-gadget-hid: alloc_chrdev_region dev: 241 0
[ 253.526405] ipod-gadget-hid: ipod_hid_alloc()
[ 253.526714] g_ipod gadget: = ipod_config_bind()
[ 253.526726] g_ipod gadget: = ipod_audio_bind()
[ 253.527897] g_ipod gadget: = ipod_hid_bind(), deactivs=1
[ 253.527936] g_ipod gadget: g_ipod ready
[ 301.615955] ipod-gadget-hid: ipod_hid_dev_open()
[ 301.615974] ipod-gadget-hid: activating
[ 301.889085] g_ipod gadget: = ipod_disconnect()
[ 301.992153] g_ipod gadget: = ipod_audio_set_alt(0,0)
[ 301.992178] g_ipod gadget: = ipod_audio_set_alt(1,0)
[ 301.992189] ipod-gadget-audio: audio stop
[ 301.992206] g_ipod gadget: = ipod_hid_set_alt()
[ 301.997021] g_ipod gadget: = ipod_hid_set_alt()
[ 302.005209] g_ipod gadget: = ipod_hid_setup()
[ 302.005233] g_ipod gadget: Control req: 81.06 v2111 i0002 l512
[ 302.005247] g_ipod gadget: get hid descriptor
[ 302.005654] g_ipod gadget: = ipod_hid_setup()
[ 302.005677] g_ipod gadget: Control req: 81.06 v2211 i0002 l512
[ 302.005690] g_ipod gadget: get hid descriptor
[ 302.007639] g_ipod gadget: = ipod_hid_setup()
[ 302.007662] g_ipod gadget: Control req: 40.40 v01f4 i01f4 l0
[ 302.007675] g_ipod gadget: apple vendor 0x40
[ 302.264696] g_ipod gadget: = ipod_hid_setup()
[ 302.264725] g_ipod gadget: Control req: 81.06 v2100 i0002 l512
[ 302.264738] g_ipod gadget: get hid descriptor
[ 335.182314] ipod-gadget-hid: ipod_hid_dev_release()
[ 335.182340] ipod-gadget-hid: deactivating=1
[ 335.182391] g_ipod gadget: = ipod_audio_disable()
[ 335.182398] ipod-gadget-audio: audio stop
[ 335.182407] g_ipod gadget: = ipod_hid_disable()
[ 335.182427] g_ipod gadget: = ipod_disconnect()

I've a feeling the hid interactions at ~ the 302.x mark should be a clue as to what happens. I've seem for others logs that they log similar, but varying numbers at this stage. Does this seem familiar to anyone? What should one expect at this stage in the dmesg log?

Thanks!
Anders