SLIP over UART device

[ofirshe]

Hey,

I have a designated UART device in my device tree and I want to run a TCP/IP application over this device. Is it possible as in Linux ?
I saw such a driver called located in zephyr\drivers\net\slip.c, but there is no DT_DRV_COMPAT so how can I link it with my device ? Or maybe I have to create one by myself.

[jukkar]

Hi, the SLIP driver in the tree is mainly used for qemu<->host communication. I have heard people using it to connect from real device so it should be possible to do what you want. If you want to try this, please consider sending patches to upstream for any needed changes.

[ofirshe]

Hey @jukkar,

Thank you very much for your answer. I would like to advice with you how should I approach this task. First, I add a line in my custom dts file zephyr,uart-pipe = &lpuart1; in 'chosen' section and also enabled CONFIG_UART_PIPE=y in my project configuration file. Once enabling UART_PIPE, this leads to CONFIG_SLIP to be enabled which results in including zephyr\drivers\net\slip.c in the build.
In order to be able to use BSD networking api, I have to enable CONFIG_NETWORKING, CONFIG_NET_SOCKETS and
CONFIG_NET_TCP also. When enabling CONFIG_NETWORKING, the build system starts searching for source files in zephyr\drivers\ethernet folder but no one found because it found in zephyr\drivers\net. Thus, I have a compilation warning:
CMake Warning at zephyr/CMakeLists.txt:824 (message):
No SOURCES given to Zephyr library: drivers__ethernet

Excluding target from build.

Should I replicate drivers\net\slip.c into zephyr\drivers\ethernet\my_custom_slip.c ?
If I will do so, I'll have two slip drivers being compiled in the same build which will trigger NET_DEVICE_INIT twice, So I'm wondering if this is the right solution.

Best regards,
Ofir.

[jukkar]

By default TAP mode (Ethernet) is set when SLIP is enabled, this requires Ethernet driver support. But there is Ethernet driver setup in drivers/net/slip.c already when TAP is enabled, so you should not need anything else for the Ethernet to be supported.
I have not done anything like this, so don't know if your setup has something wrong. But you should not need to create a new Ethernet driver as slip.c has that already.

[ofirshe]

I'm fully agree with you, but in order to use all the BSD networking api, I must enable CONFIG_NETWORKING which cause the build mechanism to search for source files in zephyr\drivers\ethernet folder. I just want to get rid of this warning
No SOURCES given to Zephyr library: drivers__ethernet

Excluding target from build.

Do you have any suggestions ?

[jukkar]

ping @pbtgit do you have any idea what might be wrong here, how did you fix you issue in #48697?

[ofirshe]

Thanks @jukkar

These are my configurations to be able to develop a simple TCP/IP application over SLIP:
CONFIG_SLIP=y
CONFIG_NET_DRIVERS=y
CONFIG_NETWORKING=y
CONFIG_NET_UDP=y
CONFIG_NET_TCP=y
CONFIG_NET_IPV4=y
CONFIG_INIT_STACKS=y
CONFIG_NET_LOG=y
CONFIG_LOG=y
CONFIG_NET_CONFIG_SETTINGS=y
CONFIG_NET_CONFIG_NEED_IPV4=y
CONFIG_NET_CONFIG_MY_IPV4_ADDR="192.0.2.1"
CONFIG_NET_SOCKETS=y
CONFIG_NET_SOCKETS_POSIX_NAMES=y
CONFIG_MAIN_STACK_SIZE=65536
CONFIG_NET_PKT_RX_COUNT=16
CONFIG_NET_PKT_TX_COUNT=16
CONFIG_NET_BUF_RX_COUNT=64
CONFIG_NET_BUF_TX_COUNT=64
CONFIG_NET_MAX_CONN=64

[jukkar]

See also #48697

[pbtgit]

As for the issues in #48697 my conclusion was that it was due to the MCU on NRF boards - The UART over MCU only worked stable with smaller packages than 64 bytes: Using the pins to physical UART worked (with HW FC), and also when using the CDC UART.
(This holds for both Zephyr and Contiki)

[pbtgit]

Yes but in my scenario it could only use L3 (only IP frames ) so there was no need for Ethernet for running SLIP.
Essentially I think the following SLIP related settings differs from yours:
CONFIG_NET_SLIP_TAP=n
CONFIG_SLIP_TAP=n
CONFIG_NET_L2_DUMMY=y

[ofirshe]

@pbtgit I see. So how should I solve this issue ? I don't want to replicate the zephyr\drivers\net\slip.c file into zephyr\drivers\ethernet directory. Do you have any suggestions or maybe open a bug for this ?

[pbtgit]

Maybe modify the build system so that zephyr\drivers\ethernet is skipped if TAP & SLIP already provides a driver in slip.c?

[ofirshe]

@pbtgit How can I do such a thing ? or maybe should I open an issue about it ?

[ofirshe]

@jukkar @pbtgit
opened a bug for it #54460