tools: Add cmux command line tool

[xiaoxiang781216]

Summary

Usage: ./nuttx/tools/cmux -d -n -b

Please refer to the following link for more information:
https://docs.kernel.org/6.1/driver-api/tty/n_gsm.html

Impact

new host tool

Testing

ci

[nuttxpr]

[Experimental Bot, please feedback here]

No, this PR does not fully meet the NuttX requirements. While it provides a summary and mentions testing via CI, several crucial pieces of information are missing.

Here's a breakdown of what's lacking:

• Insufficient Summary Detail: The summary provides basic usage but doesn't explain why this new tool is necessary. What problem does it solve? What existing functionality does it improve upon (or replace)? How does it work internally? Are there related NuttX issues?

• Missing Impact Assessment: Simply stating "new host tool" is insufficient. Consider the impact points listed in the requirements:

  • Feature: Is it a new feature? Or does it replace/modify an existing one?
  • User Impact: How will users interact with this tool? Will existing workflows change?
  • Build Impact: Does adding this tool require changes to the NuttX build system? Does it introduce new dependencies?
  • Hardware Impact: Does this tool interact with hardware in any specific way? Is it architecture-specific?
  • Documentation: This new tool requires documentation explaining its purpose, usage, and options.
  • Security/Compatibility: These points haven't been addressed. Even if the impact is "NO," it should be explicitly stated.

• Inadequate Testing Information: "ci" is not enough. While CI testing is important, the PR needs to show specific test results.

  • Build Host Details: Specify the OS, CPU architecture, and compiler version used for testing.
  • Target Details: Which architecture(s) and board configurations was this tested on? Was it tested on real hardware or a simulator?
  • Logs: The PR needs to include "before" and "after" logs demonstrating the tool's functionality and the problem it solves (or the improvement it delivers). Simply saying "ci" provides no evidence that the tool actually works.

In short, the PR needs to be significantly more detailed to meet the NuttX requirements. It needs to provide a thorough explanation of the changes, their impact, and clear evidence of testing.

[acassis]

@xiaoxiang781216 I think this application depends on CMUX support in the NuttX kernel, is there a CMUX driver coming to NuttX kernel?

[acassis]

@xiaoxiang781216 I was thinking this was CMUX support for NuttX, but seems like it has other purpose, probably to run on Linux side. Could you please explain the idea of this tool? Please create a usage() function explain the purpose of this tool.

[xiaoxiang781216]

@xiaoxiang781216 I think this application depends on CMUX support in the NuttX kernel, is there a CMUX driver coming to NuttX kernel?

Yes, it will come in the next patch.

[hartmannathan]

Please could you add a brief explanation what is cmux and what it is for in the PR description and commit log? Thanks.

[xiaoxiang781216]

@xiaoxiang781216 I was thinking this was CMUX support for NuttX, but seems like it has other purpose, probably to run on Linux side. Could you please explain the idea of this tool? Please create a usage() function explain the purpose of this tool.

already in the code:

static void usage(const char *progname)
{
  fprintf(stderr, "Usage: %s -d <device> -n <number> -b <baudrate>\n",
          progname);
  exit(EXIT_FAILURE);
}

[xiaoxiang781216]

Please could you add a brief explanation what is cmux and what it is for in the PR description and commit log? Thanks.

Update, you can learn the concept and spec from:
https://docs.kernel.org/6.1/driver-api/tty/n_gsm.html

[acassis]

Please could you add a brief explanation what is cmux and what it is for in the PR description and commit log? Thanks.

Update, you can learn the concept and spec from: https://docs.kernel.org/6.1/driver-api/tty/n_gsm.html

Thank you Xiang! What is the purpose of this external too to NuttX, since NuttX doesn't have CMUX support yet?

I think this is the question I and everybody that find this program at nuttx/tools/ will ask. This application is for Linux, not for NuttX, correct?

[acassis]

@xiaoxiang781216 I think /me and @hartmannathan are asking some question: why to include a program that is supported only for Linux into NuttX? The documentation you provided is for Linux, please consider including a Documentation/ to explain the goal and purpose to have a Linux host CMUX GSM instead of adding CMUX support on NuttX and adding this cmux tool at nuttx-apps

[acassis]

@xiaoxiang781216 there is an issue already opened asking for CMUX support on NuttX: #7153

[acassis]

@xiaoxiang781216 I think this application depends on CMUX support in the NuttX kernel, is there a CMUX driver coming to NuttX kernel?

Yes, it will come in the next patch.

But in this case the cmux application should be inside nuttx-apps, instead of nuttx/tools/, right?

[xiaoxiang781216]

Please could you add a brief explanation what is cmux and what it is for in the PR description and commit log? Thanks.

Update, you can learn the concept and spec from: https://docs.kernel.org/6.1/driver-api/tty/n_gsm.html

Thank you Xiang! What is the purpose of this external too to NuttX, since NuttX doesn't have CMUX support yet?

I think this is the question I and everybody that find this program at nuttx/tools/ will ask. This application is for Linux, not for NuttX, correct?

Yes, that's why this tool is put into nuttx/tools, not apps/.

@xiaoxiang781216 I think /me and @hartmannathan are asking some question: why to include a program that is supported only for Linux into NuttX?

Because you need this tool to change host serial port into mux mode.

The documentation you provided is for Linux, please consider including a Documentation/ to explain the goal and purpose to have a Linux host CMUX GSM

@Gary-Hobson will provide a NuttX serial driver which implement CMUX protocol.

instead of adding CMUX support on NuttX and adding this cmux tool at nuttx-apps

This tool doesn't need for NuttX since NuttX CMUX driver auto switch to mux mode by config, not through ioctl dynamically.

@xiaoxiang781216 I think this application depends on CMUX support in the NuttX kernel, is there a CMUX driver coming to NuttX kernel?

@xiaoxiang781216 there is an issue already opened asking for CMUX support on NuttX: #7153

Yes, after @Gary-Hobson upstream MUX serial driver, #7153 could be closed as complete.

Yes, it will come in the next patch.

But in this case the cmux application should be inside nuttx-apps, instead of nuttx/tools/, right?

No, NuttX mux driver could work automatically without the setup like Linux, that's why this tool put into nuttx/tools/ not apps/.

[acassis]

Please could you add a brief explanation what is cmux and what it is for in the PR description and commit log? Thanks.

Update, you can learn the concept and spec from: https://docs.kernel.org/6.1/driver-api/tty/n_gsm.html

Thank you Xiang! What is the purpose of this external too to NuttX, since NuttX doesn't have CMUX support yet?
I think this is the question I and everybody that find this program at nuttx/tools/ will ask. This application is for Linux, not for NuttX, correct?

Yes, that's why this tool is put into nuttx/tools, not apps/.

@xiaoxiang781216 I think /me and @hartmannathan are asking some question: why to include a program that is supported only for Linux into NuttX?

Because you need this tool to change host serial port into mux mode.

Why? Are you using the modem with SIM? Normally the CMUX will work integrated with PPP and the user should issue a command (or an IOCTL) to setup the CMUX (multiplexed) ports.

The documentation you provided is for Linux, please consider including a Documentation/ to explain the goal and purpose to have a Linux host CMUX GSM

@Gary-Hobson will provide a NuttX serial driver which implement CMUX protocol.

Great! Kudos @Gary-Hobson !

instead of adding CMUX support on NuttX and adding this cmux tool at nuttx-apps

This tool doesn't need for NuttX since NuttX CMUX driver auto switch to mux mode by config, not through ioctl dynamically.

Hmm, I think having IOCTL support could be useful in case where we want to enter / leave CMUX during the PPP execution.

@xiaoxiang781216 I think this application depends on CMUX support in the NuttX kernel, is there a CMUX driver coming to NuttX kernel?

@xiaoxiang781216 there is an issue already opened asking for CMUX support on NuttX: #7153

Yes, after @Gary-Hobson upstream MUX serial driver, #7153 could be closed as complete.

Yes, it will come in the next patch.

But in this case the cmux application should be inside nuttx-apps, instead of nuttx/tools/, right?

No, NuttX mux driver could work automatically without the setup like Linux, that's why this tool put into nuttx/tools/ not apps/.

Hmm, by automatically you mean statically, right? It should be use some board config to enter in this CMUX mode, correct?

[acassis]

@xiaoxiang781216 maybe you can include a verbose explanation inside this C file (just before "Included Files") explaining the purpose of this file inside nuttx/tools. This way it could help the absence of proper Documentation/ to this script

[xiaoxiang781216]

Because you need this tool to change host serial port into mux mode.

Why? Are you using the modem with SIM?

We use cmux for debugging purpose to have the multiple virtual port for nsh/log/gdb at the same time on one physical uart.

Normally the CMUX will work integrated with PPP and the user should issue a command (or an IOCTL) to setup the CMUX (multiplexed) ports.

in this case, you can bypass cmux tool and do ioctl in your program.

This tool doesn't need for NuttX since NuttX CMUX driver auto switch to mux mode by config, not through ioctl dynamically.

Hmm, I think having IOCTL support could be useful in case where we want to enter / leave CMUX during the PPP execution.

it's hard to handle the enter/leave without the lost data, especially we want syslog can be worked as soon as possible in any environment.

No, NuttX mux driver could work automatically without the setup like Linux, that's why this tool put into nuttx/tools/ not apps/.

Hmm, by automatically you mean statically, right? It should be use some board config to enter in this CMUX mode, correct?

you can config through:

1. Which physical port you want to use CMUX
2. how many virtual serial ports you want

After initialization, you will see all virtual serial ports under /dev/ and use them like the normal uart. Of course, the other side(e.g. Linux) need config by their design as usually.

[Gary-Hobson]

The nuttx kernel cmux driver support has been completed, but the internal review has not been completed (need to support sending and receiving data in interrupts).

Maybe I can upload the cmux driver in thread mode to the community for review tomorrow (does not support sending and receiving data in interrupts)

Currently, it has been verified that it can communicate with the linux kernel, and multiple gsmtty devices can be virtualized in the linux kernel (using cmux tools to configure linux), and the corresponding tty driver will also be generated in the nuttx kernel

PPP communication with modem is still to be verified

[acassis]

@xiaoxiang781216 please include an explanation in the source code or a Documentation/ about this script, to avoid having another script that nobody knows why it is inside nuttx

[acassis]

@xiaoxiang781216 I think mknod will require root access, doesn't it?