Okay now I can compile the firmware with the Codec for SGTL5000 I'm hanging again.
The kernel module is loaded but a cat /proc/asound/cards lists still --- so soundcards --- I'm not really sure but I think I just have a codec installed but no "card". Am I right if I think I need a card driver in build_dir/target-mipsel_24kc_musl/linux-ramips_mt7688/linux-4.4.52/sound/soc/mediatek which 'uses' the codec?
Does anyone know how to get this thing up and running? It's so exhausting...
regards, Christopher

@WereCatf yikes. It works thanks a lot

without. Should I try again with -n?

@WereCatf ok., thank you so far. I revert the changes made on .config file and build the image once again. Just changed target profile to onion omega2.
After flashing no wifi net is created (tried with pc and android phone [wifi analyzer]).
Output of dmesg is

dmesg
[    0.000000] Linux version 4.4.52 (chrimbo@helios) (gcc version 5.4.0 (LEDE GCC 5.4.0 r3660+10-5087b40) ) #0 Sun Mar 5 18:23:05 2017
[    0.000000] Board has DDR2
[    0.000000] Analog PMU set to hw control
[    0.000000] Digital PMU set to hw control
[    0.000000] SoC Type: MediaTek MT7688 ver:1 eco:2
[    0.000000] bootconsole [early0] enabled
[    0.000000] CPU0 revision is: 00019655 (MIPS 24KEc)
[    0.000000] MIPS: machine is Onion Omega2
[    0.000000] Determined physical RAM map:
[    0.000000]  memory: 04000000 @ 00000000 (usable)
[    0.000000] Initrd not found or empty - disabling initrd
[    0.000000] Zone ranges:
[    0.000000]   Normal   [mem 0x0000000000000000-0x0000000003ffffff]
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000000000000-0x0000000003ffffff]
[    0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x0000000003ffffff]
[    0.000000] On node 0 totalpages: 16384
[    0.000000] free_area_init_node: node 0, pgdat 803ee440, node_mem_map 81000000
[    0.000000]   Normal zone: 128 pages used for memmap
[    0.000000]   Normal zone: 0 pages reserved
[    0.000000]   Normal zone: 16384 pages, LIFO batch:3
[    0.000000] Primary instruction cache 64kB, VIPT, 4-way, linesize 32 bytes.
[    0.000000] Primary data cache 32kB, 4-way, PIPT, no aliases, linesize 32 bytes
[    0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
[    0.000000] pcpu-alloc: [0] 0
[    0.000000] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 16256
[    0.000000] Kernel command line: console=ttyS0,115200 rootfstype=squashfs,jffs2
[    0.000000] PID hash table entries: 256 (order: -2, 1024 bytes)
[    0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
[    0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
[    0.000000] Writing ErrCtl register=00035af0
[    0.000000] Readback ErrCtl register=00035af0
[    0.000000] Memory: 60396K/65536K available (3239K kernel code, 153K rwdata, 748K rodata, 140K init, 206K bss, 5140K reserved, 0K cma-reserved)
[    0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[    0.000000] NR_IRQS:256
[    0.000000] intc: using register map from devicetree
[    0.000000] CPU Clock: 580MHz
[    0.000000] clocksource_probe: no matching clocksources found
[    0.000000] clocksource: MIPS: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 6590553264 ns
[    0.000010] sched_clock: 32 bits at 290MHz, resolution 3ns, wraps every 7405115902ns
[    0.007529] Calibrating delay loop... 385.84 BogoMIPS (lpj=1929216)
[    0.070047] pid_max: default: 32768 minimum: 301
[    0.074652] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.080994] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.088857] Initializing cgroup subsys io
[    0.092725] Initializing cgroup subsys devices
[    0.096963] Initializing cgroup subsys freezer
[    0.101245] Initializing cgroup subsys net_cls
[    0.105537] Initializing cgroup subsys pids
[    0.115447] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[    0.124975] futex hash table entries: 256 (order: -1, 3072 bytes)
[    0.131060] pinctrl core: initialized pinctrl subsystem
[    0.137466] NET: Registered protocol family 16
[    0.162359] mt7621_gpio 10000600.gpio: registering 32 gpios
[    0.167895] mt7621_gpio 10000600.gpio: registering 32 gpios
[    0.173338] mt7621_gpio 10000600.gpio: registering 32 gpios
[    0.180415] clocksource: Switched to clocksource MIPS
[    0.186781] NET: Registered protocol family 2
[    0.192062] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[    0.198758] TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
[    0.204946] TCP: Hash tables configured (established 1024 bind 1024)
[    0.211143] UDP hash table entries: 256 (order: 0, 4096 bytes)
[    0.216741] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[    0.223134] NET: Registered protocol family 1
[    0.227353] PCI: CLS 0 bytes, default 32
[    0.250939] squashfs: version 4.0 (2009/01/31) Phillip Lougher
[    0.256530] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[    0.269541] io scheduler noop registered
[    0.273343] io scheduler deadline registered (default)
[    0.279125] rt2880-pinmux pinctrl: pin io18 already requested by pinctrl; cannot claim for 10005000.pwm
[    0.288204] rt2880-pinmux pinctrl: pin-18 (10005000.pwm) status -22
[    0.294212] rt2880-pinmux pinctrl: could not request pin 18 (io18) from group pwm0  on device rt2880-pinmux
[    0.303616] mtk-pwm 10005000.pwm: Error applying setting, reverse things back
[    0.310973] Serial: 8250/16550 driver, 16 ports, IRQ sharing enabled
[    0.320703] console [ttyS0] disabled
[    0.324135] 10000c00.uartlite: ttyS0 at MMIO 0x10000c00 (irq = 28, base_baud = 2500000) is a 16550A
[    0.332892] console [ttyS0] enabled
[    0.339874] bootconsole [early0] disabled
[    0.348530] 10000d00.uart1: ttyS1 at MMIO 0x10000d00 (irq = 29, base_baud = 2500000) is a 16550A
[    0.358062] 10000e00.uart2: ttyS2 at MMIO 0x10000e00 (irq = 30, base_baud = 2500000) is a 16550A
[    0.368839] spi-mt7621 10000b00.spi: sys_freq: 193333333
[    0.381213] m25p80 spi32766.0: using chunked io (size=31)
[    0.386703] m25p80 spi32766.0: w25q128 (16384 Kbytes)
[    0.391910] 4 ofpart partitions found on MTD device spi32766.0
[    0.397824] Creating 4 MTD partitions on "spi32766.0":
[    0.403051] 0x000000000000-0x000000030000 : "u-boot"
[    0.409945] 0x000000030000-0x000000040000 : "u-boot-env"
[    0.417347] 0x000000040000-0x000000050000 : "factory"
[    0.424419] 0x000000050000-0x000001000000 : "firmware"
[    0.451922] 2 uimage-fw partitions found on MTD device firmware
[    0.457958] 0x000000050000-0x0000001a2478 : "kernel"
[    0.464670] 0x0000001a2478-0x000001000000 : "rootfs"
[    0.471646] mtd: device 5 (rootfs) set to be root filesystem
[    0.477457] 1 squashfs-split partitions found on MTD device rootfs
[    0.483797] 0x000000750000-0x000001000000 : "rootfs_data"
[    0.501189] rt3050-esw 10110000.esw: link changed 0x00
[    0.509061] mtk_soc_eth 10100000.ethernet eth0: mediatek frame engine at 0xb0100000, irq 5
[    0.518012] mt7621_wdt 10000120.watchdog: Initialized
[    0.524745] NET: Registered protocol family 10
[    0.532873] NET: Registered protocol family 17
[    0.537477] bridge: automatic filtering via arp/ip/ip6tables has been deprecated. Update your scripts to load br_netfilter if you need this.
[    0.550343] 8021q: 802.1Q VLAN Support v1.8
[    0.562671] VFS: Mounted root (squashfs filesystem) readonly on device 31:5.
[    0.570661] Freeing unused kernel memory: 140K (8040d000 - 80430000)
[    1.898544] init: Console is alive
[    1.902309] init: - watchdog -
[    5.069529] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[    5.223874] usbcore: registered new interface driver usbfs
[    5.229578] usbcore: registered new interface driver hub
[    5.235118] usbcore: registered new device driver usb
[    5.412785] raid6: int32x1  gen()    25 MB/s
[    5.580664] raid6: int32x1  xor()    42 MB/s
[    5.750514] raid6: int32x2  gen()    48 MB/s
[    5.920719] raid6: int32x2  xor()    49 MB/s
[    6.090939] raid6: int32x4  gen()    66 MB/s
[    6.260602] raid6: int32x4  xor()    48 MB/s
[    6.430900] raid6: int32x8  gen()    73 MB/s
[    6.600534] raid6: int32x8  xor()    55 MB/s
[    6.604865] raid6: using algorithm int32x8 gen() 73 MB/s
[    6.610245] raid6: .... xor() 55 MB/s, rmw enabled
[    6.615113] raid6: using intx1 recovery algorithm
[    6.621314] xor: measuring software checksum speed
[    6.720416]    8regs     :   418.400 MB/sec
[    6.820413]    8regs_prefetch:   398.400 MB/sec
[    6.920418]    32regs    :   499.200 MB/sec
[    7.020415]    32regs_prefetch:   459.200 MB/sec
[    7.025097] xor: using function: 32regs (499.200 MB/sec)
[    7.363418] Btrfs loaded
[    7.373120] exFAT: Version 1.2.9
[    7.418703] SCSI subsystem initialized
[    7.429597] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
[    7.438184] ehci-platform: EHCI generic platform driver
[    7.453886] phy phy-10120000.usbphy.0: remote usb device wakeup disabled
[    7.460706] phy phy-10120000.usbphy.0: UTMI 16bit 30MHz
[    7.466036] ehci-platform 101c0000.ehci: EHCI Host Controller
[    7.471911] ehci-platform 101c0000.ehci: new USB bus registered, assigned bus number 1
[    7.480058] ehci-platform 101c0000.ehci: irq 26, io mem 0x101c0000
[    7.500461] ehci-platform 101c0000.ehci: USB 2.0 started, EHCI 1.00
[    7.507983] hub 1-0:1.0: USB hub found
[    7.512257] hub 1-0:1.0: 1 port detected
[    7.521572] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
[    7.529626] ohci-platform: OHCI generic platform driver
[    7.535280] ohci-platform 101c1000.ohci: Generic Platform OHCI controller
[    7.542256] ohci-platform 101c1000.ohci: new USB bus registered, assigned bus number 2
[    7.550377] ohci-platform 101c1000.ohci: irq 26, io mem 0x101c1000
[    7.615576] hub 2-0:1.0: USB hub found
[    7.619865] hub 2-0:1.0: 1 port detected
[    7.637708] MTK MSDC device init.
[    7.680582] mtk-sd: MediaTek MT6575 MSDC Driver
[    7.688690] sdhci: Secure Digital Host Controller Interface driver
[    7.695035] sdhci: Copyright(c) Pierre Ossman
[    7.700976] sdhci-pltfm: SDHCI platform and OF driver helper
[    7.711754] usbcore: registered new interface driver usb-storage
[    7.721723] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[    7.739536] init: - preinit -
[    8.400544] usb 2-1: new full-speed USB device number 2 using ohci-platform
[    8.765863] rt3050-esw 10110000.esw: link changed 0x00
[    8.861827] hub 2-1:1.0: USB hub found
[    8.870048] hub 2-1:1.0: 3 ports detected
[    8.956364] random: procd: uninitialized urandom read (4 bytes read, 16 bits of entropy available)
[   12.217783] mount_root: loading kmods from internal overlay
[   12.255990] kmodloader: loading kernel modules from //etc/modules-boot.d/*
[   12.268422] kmodloader: done loading kernel modules from //etc/modules-boot.d/*
[   13.277345] jffs2: notice: (437) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
[   13.293672] block: attempting to load /tmp/jffs_cfg/upper/etc/config/fstab
[   13.304496] block: extroot: not configured
[   13.382490] jffs2: notice: (434) jffs2_build_xattr_subsystem: complete building xattr subsystem, 0 of xdatum (0 unchecked, 0 orphan) and 0 of xref (0 dead, 0 orphan) found.
[   14.031603] block: attempting to load /tmp/jffs_cfg/upper/etc/config/fstab
[   14.041503] block: extroot: not configured
[   14.047129] mount_root: overlay filesystem has not been fully initialized yet
[   14.126053] mount_root: switching to jffs2 overlay
[   14.886701] urandom-seed: Seed file not found (/etc/urandom.seed)
[   14.996254] procd: - early -
[   14.999288] procd: - watchdog -
[   15.743960] procd: - ubus -
[   15.797331] random: ubusd: uninitialized urandom read (4 bytes read, 27 bits of entropy available)
[   15.807016] random: ubusd: uninitialized urandom read (4 bytes read, 27 bits of entropy available)
[   15.816248] random: ubusd: uninitialized urandom read (4 bytes read, 27 bits of entropy available)
[   15.829658] random: ubusd: uninitialized urandom read (4 bytes read, 27 bits of entropy available)
[   15.838884] random: ubusd: uninitialized urandom read (4 bytes read, 27 bits of entropy available)
[   15.848248] random: ubusd: uninitialized urandom read (4 bytes read, 27 bits of entropy available)
[   15.857587] random: ubusd: uninitialized urandom read (4 bytes read, 27 bits of entropy available)
[   15.867166] procd: - init -
[   16.322786] kmodloader: loading kernel modules from /etc/modules.d/*
[   16.400337] ntfs: driver 2.1.32 [Flags: R/O MODULE].
[   16.485459] ip6_tables: (C) 2000-2006 Netfilter Core Team
[   16.510983] Loading modules backported from Linux version wt-2017-01-31-0-ge882dff19e7f
[   16.519109] Backport generated by backports.git backports-20160324-13-g24da7d3c
[   16.593978] i2c /dev entries driver
[   16.601734] mt76_wmac 10300000.wmac: ASIC revision: 76280001
[   18.730783] mt76_wmac 10300000.wmac: Firmware Version: _e2_mp
[   18.736631] mt76_wmac 10300000.wmac: Build Time: 20150211175503
[   18.760431] firmware init done
[   18.933442] ieee80211 phy0: Selected rate control algorithm 'minstrel_ht'
[   19.124376] gdma-rt2880 10002800.gdma: revision: 3, channels: 16
[   19.265830] i2c-mt7621 10000900.i2c: clock 100KHz, re-start not support
[   19.298053] Linux video capture interface: v2.00
[   19.317165] hidraw: raw HID events driver (C) Jiri Kosina
[   19.528036] fuse init (API version 7.23)
[   19.608856] Bluetooth: Core ver 2.21
[   19.612677] NET: Registered protocol family 31
[   19.617184] Bluetooth: HCI device and connection manager initialized
[   19.623663] Bluetooth: HCI socket layer initialized
[   19.628613] Bluetooth: L2CAP socket layer initialized
[   19.633787] Bluetooth: SCO socket layer initialized
[   19.691738] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[   19.697139] Bluetooth: BNEP filters: protocol multicast
[   19.702503] Bluetooth: BNEP socket layer initialized
[   19.731749] usbcore: registered new interface driver btusb
[   19.768258] usbcore: registered new interface driver cdc_acm
[   19.774083] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters
[   19.787403] Bluetooth: HCI UART driver ver 2.3
[   19.791988] Bluetooth: HCI UART protocol H4 registered
[   19.797197] Bluetooth: HCI UART protocol BCSP registered
[   19.802596] Bluetooth: HCI UART protocol ATH3K registered
[   19.812466] Bluetooth: HIDP (Human Interface Emulation) ver 1.2
[   19.818495] Bluetooth: HIDP socket layer initialized
[   19.827193] ip_tables: (C) 2000-2006 Netfilter Core Team
[   19.855910] nf_conntrack version 0.5.0 (945 buckets, 3780 max)
[   19.918748] Bluetooth: RFCOMM TTY layer initialized
[   19.923795] Bluetooth: RFCOMM socket layer initialized
[   19.929032] Bluetooth: RFCOMM ver 1.11
[   19.954056] usbcore: registered new interface driver ums-alauda
[   19.963486] usbcore: registered new interface driver ums-cypress
[   19.973208] usbcore: registered new interface driver ums-datafab
[   19.982551] usbcore: registered new interface driver ums-freecom
[   19.992151] usbcore: registered new interface driver ums-isd200
[   20.001921] usbcore: registered new interface driver ums-jumpshot
[   20.011477] usbcore: registered new interface driver ums-karma
[   20.021979] usbcore: registered new interface driver ums-sddr09
[   20.031574] usbcore: registered new interface driver ums-sddr55
[   20.041661] usbcore: registered new interface driver ums-usbat
[   20.055081] usbcore: registered new interface driver usbhid
[   20.060789] usbhid: USB HID core driver
[   20.069173] usbcore: registered new interface driver usblp
[   20.085259] usbcore: registered new interface driver usbserial
[   20.091356] usbcore: registered new interface driver usbserial_generic
[   20.098093] usbserial: USB Serial support registered for generic
[   20.119171] Driver for 1-wire Dallas network protocol.
[   20.148417] xt_time: kernel timezone is -0000
[   20.155364] usbcore: registered new interface driver ch341
[   20.161135] usbserial: USB Serial support registered for ch341-uart
[   20.169992] usbcore: registered new interface driver cp210x
[   20.175854] usbserial: USB Serial support registered for cp210x
[   20.185549] usbcore: registered new interface driver ftdi_sio
[   20.191580] usbserial: USB Serial support registered for FTDI USB Serial Device
[   20.210997] usbcore: registered new interface driver pl2303
[   20.216765] usbserial: USB Serial support registered for pl2303
[   20.228792] PPP generic driver version 2.4.2
[   20.236642] NET: Registered protocol family 24
[   20.256365] usbcore: registered new interface driver snd-usb-audio
[   20.274756] usbcore: registered new interface driver uvcvideo
[   20.280659] USB Video Class driver (1.1.1)
[   20.293529] kmodloader: done loading kernel modules from /etc/modules.d/*
[   20.546193] random: jshn: uninitialized urandom read (4 bytes read, 35 bits of entropy available)
[   20.632899] random: jshn: uninitialized urandom read (4 bytes read, 35 bits of entropy available)
[   30.403439] device eth0.1 entered promiscuous mode
[   30.408316] device eth0 entered promiscuous mode
[   30.441641] br-wlan: port 1(eth0.1) entered forwarding state
[   30.447462] br-wlan: port 1(eth0.1) entered forwarding state
[   32.440479] br-wlan: port 1(eth0.1) entered forwarding state
[   76.730473] random: nonblocking pool is initialized

@Andrew-Marshall I think you mean ls --all, otherwise you specify two times the l option :-). You can also use ls -a as a shortcut.
Now to your Problem. ls -a lists at least two items: . and ..
. is the current directory and
.. is the parent directory
Typically if you connect through ssh your working directory is the home directory of the user you're logged in. Mostly root on omega2. That menas you start in /root as your working directory. If you haven't copied anything to this place it should be empty and ls -al returns just these two directories.

root@omega:~ ls -a
. ..

you may change the directory to the root (root of filesystem, not home directory of root, the difference is / and /root/) by executing

cd /

I hope it helps

Edit: I forget your other problem. Do you use an adblocker, scriptblocker or anything like that? I had to allow the omega2 in noScript (firefox plugin) to open the omega console

Hello together,

this is how I fixed it to get compiled. Many thanks to @WereCatf

git diff package/kernel/linux/modules/sound.mkdiff --git a/package/kernel/linux/modules/sound.mk b/package/kernel/linux/modules/sound.mk
index de5d8fc..042cdc4 100644
--- a/package/kernel/linux/modules/sound.mk
+++ b/package/kernel/linux/modules/sound.mk
@@ -519,3 +519,19 @@ define KernelPackage/sound-hda-intel/description
 endef
 
 $(eval $(call KernelPackage,sound-hda-intel))
+
+define KernelPackage/sound-soc-sgtl5000
+  TITLE:=Support for SGTL5000
+  KCONFIG:=CONFIG_SND_SOC_SGTL5000
+  FILES:=\
+       $(LINUX_DIR)/sound/soc/codecs/snd-soc-sgtl5000.ko
+  AUTOLOAD:=$(call AutoLoad,57,snd-soc-sgtl5000)
+  DEPENDS:=+kmod-i2c-core +kmod-regmap +kmod-sound-soc-core
+  $(call AddDepends/sound)
+endef
+
+define KernelPackage/sound-soc-sgtl5000/description
+  Support for the SGTL5000 codec
+endef
+
+$(eval $(call KernelPackage,sound-soc-sgtl5000))

Now I have some new problems using wifi. After solving that I'll focus again on the audio part.
Here is the follow up thread

Hello,

I compiled a firmware using lede. The config file is attached here When trying to execute wifisetup I'm prompted to choose which network I want to connect to. I choose one, enter the password and get this message:

Connecting to Compoglobal network using intf 0...
ra0(ralink): Interface type not supported
'radio0' is disabled
ra0(ralink): Interface type not supported
'radio0' is disabled
> Checking wwan device status...
> wwan is not up!!
> Checking internet connection...

ifconfig outputs:

br-wlan   Link encap:Ethernet  HWaddr 40:A3:6B:C0:A0:69
          inet addr:192.168.3.1  Bcast:192.168.3.255  Mask:255.255.255.0
          inet6 addr: fe80::42a3:6bff:fec0:a069/64 Scope:Link
          inet6 addr: fd1d:48c4:7633::1/60 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:41 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:8307 (8.1 KiB)

eth0      Link encap:Ethernet  HWaddr 40:A3:6B:C0:A0:69
          inet6 addr: fe80::42a3:6bff:fec0:a069/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:105 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:25528 (24.9 KiB)
          Interrupt:5

eth0.1    Link encap:Ethernet  HWaddr 40:A3:6B:C0:A0:69
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:41 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:8307 (8.1 KiB)

eth0.2    Link encap:Ethernet  HWaddr 40:A3:6B:C0:A0:69
          inet6 addr: fe80::42a3:6bff:fec0:a069/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:39 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:11457 (11.1 KiB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:56 errors:0 dropped:0 overruns:0 frame:0
          TX packets:56 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1
          RX bytes:3752 (3.6 KiB)  TX bytes:3752 (3.6 KiB)

sometimes when I run wifisetup the omega2 reboots

Best regards
Christopher

I made some progress of that. I'll post it the next days.

@WereCatf Ok, I modified sound.mk and eventually I could select the option in menuconfig. But compiling fails because snd-soc-sgtl5000.ko was not found

ERROR: module '/sound/soc/codecs/snd-soc-sgtl5000.ko' is missing.

The source is available

ls build_dir/toolchain-mipsel_24kc_gcc-5.4.0_musl/linux-4.4.52/sound/soc/codecs/ |grep sgtl
sgtl5000.c
sgtl5000.h

Edit: it was just a Typo
Now I think it was compiled, at least I got linux-ramips_mt7688/linux-4.4.52/sound/soc/codecs/snd-soc-sgtl5000.ko
but

Package kmod-sound-soc-sgtl5000 is missing dependencies for the following libraries:
i2c-core.ko
regmap-core.ko
regmap-i2c.ko
snd-soc-core.ko
modules/sound.mk:537: recipe for target '/home/chrimbo/workspace/omega/bin/targets/ramips/mt7688/packages/kmod-sound-soc-sgtl5000_4.4.52-1_mipsel_24kc.ipk' failed

Espacially i2c-core.komakes me headache, why is the i2c-core kernel module missing?

Again thanks for your help and patience

@WereCatf Oh, sorry for confusing you. It is both. The audio data is transferred by I²S but the controlling information is using I²C. I cloned https://github.com/WereCatf/source and ran first_time_setup.sh, which, I assume, calls make menuconfig. I did not find an option for SGTL5000
I'm really sorry for bothering you, but it's the first time for me to dig into SBCs that deeply.