[musl] Question: Support for custom (non-standard) baud rates in musl

[musl] Question: Support for custom (non-standard) baud rates in musl

[Dora, Sunil Kumar]

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Hi,
I am currently investigating a build issue in GDB related to setting custom (non-standard) baud rates on Linux.
From reviewing musl's termios implementation, I noticed:

  *
cfsetospeed / cfsetispeed appear to return EINVAL for non-standard baud rates.
  *
The c_ispeed / c_ospeed fields are not exposed with the same naming as in glibc.
  *
Linux-specific interfaces such as termios2, BOTHER, TCGETS2, etc., are not visible through the standard musl headers.

I would like to confirm whether the lack of support for arbitrary/custom baud rates (via BOTHER / termios2) is an intentional design decision in musl.
If custom baud rates are expected to work on musl-based Linux systems, I would appreciate guidance on the correct and supported approach.
Thank you for your time.
Best regards,
Sunil Dora


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Re: [musl] Question: Support for custom (non-standard) baud rates in musl

[Markus Wichmann]

Am Wed, Feb 11, 2026 at 08:33:46PM +0000 schrieb Dora, Sunil Kumar:
> Hi,
> I am currently investigating a build issue in GDB related to setting custom (non-standard) baud rates on Linux.
> From reviewing musl's termios implementation, I noticed:
> 
>   *
> cfsetospeed / cfsetispeed appear to return EINVAL for non-standard baud rates.
>   *
> The c_ispeed / c_ospeed fields are not exposed with the same naming as in glibc.
>   *
> Linux-specific interfaces such as termios2, BOTHER, TCGETS2, etc., are not visible through the standard musl headers.
> 
> I would like to confirm whether the lack of support for arbitrary/custom baud rates (via BOTHER / termios2) is an intentional design decision in musl.
> If custom baud rates are expected to work on musl-based Linux systems, I would appreciate guidance on the correct and supported approach.
> Thank you for your time.
> Best regards,
> Sunil Dora
> 

There is currently no support for arbitrary baud rates. If it is ever
added, then likely via cfsetospeed().

Ciao,
Markus

Re: [musl] Question: Support for custom (non-standard) baud rates in musl

[Rich Felker]

On Wed, Feb 11, 2026 at 08:33:46PM +0000, Dora, Sunil Kumar wrote:
> Hi,
> I am currently investigating a build issue in GDB related to setting custom (non-standard) baud rates on Linux.
> >From reviewing musl's termios implementation, I noticed:
> 
>   *
> cfsetospeed / cfsetispeed appear to return EINVAL for non-standard baud rates.
>   *
> The c_ispeed / c_ospeed fields are not exposed with the same naming as in glibc.
>   *
> Linux-specific interfaces such as termios2, BOTHER, TCGETS2, etc., are not visible through the standard musl headers.
> 
> I would like to confirm whether the lack of support for arbitrary/custom baud rates (via BOTHER / termios2) is an intentional design decision in musl.
> If custom baud rates are expected to work on musl-based Linux systems, I would appreciate guidance on the correct and supported approach.

There was a thread on this topic a while back,
https://www.openwall.com/lists/musl/2024/04/11/5

I don't think we arrived at any good conclusion for the right way to
support this.

Rich

Re: [musl] Question: Support for custom (non-standard) baud rates in musl

[Dora, Sunil Kumar]

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Hi Rich,

Thanks for the reference and for pointing me to that thread — that’s helpful.
I’ll take this into account while preparing the GDB fix.

Best regards,
Sunil
________________________________
From: Rich Felker <dalias@libc.org>
Sent: Thursday, February 12, 2026 9:46 PM
To: Dora, Sunil Kumar <SunilKumar.Dora@windriver.com>
Cc: musl@lists.openwall.com <musl@lists.openwall.com>; Kokkonda, Sundeep <Sundeep.Kokkonda@windriver.com>
Subject: Re: [musl] Question: Support for custom (non-standard) baud rates in musl

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On Wed, Feb 11, 2026 at 08:33:46PM +0000, Dora, Sunil Kumar wrote:
> Hi,
> I am currently investigating a build issue in GDB related to setting custom (non-standard) baud rates on Linux.
> >From reviewing musl's termios implementation, I noticed:
>
>   *
> cfsetospeed / cfsetispeed appear to return EINVAL for non-standard baud rates.
>   *
> The c_ispeed / c_ospeed fields are not exposed with the same naming as in glibc.
>   *
> Linux-specific interfaces such as termios2, BOTHER, TCGETS2, etc., are not visible through the standard musl headers.
>
> I would like to confirm whether the lack of support for arbitrary/custom baud rates (via BOTHER / termios2) is an intentional design decision in musl.
> If custom baud rates are expected to work on musl-based Linux systems, I would appreciate guidance on the correct and supported approach.

There was a thread on this topic a while back,
https://www.openwall.com/lists/musl/2024/04/11/5

I don't think we arrived at any good conclusion for the right way to
support this.

Rich

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