Re: [PATCH v2 2/3] linux/termios: factor out the kernel interface from termios_internal.h

[H. Peter Anvin]

On September 17, 2025 6:05:05 AM PDT, Adhemerval Zanella Netto <adhemerval.zanella@linaro.org> wrote:
>
>
>On 10/09/25 18:36, H. Peter Anvin wrote:
>> Factor out the internal kernel interface from termios_internal.h, so
>> that it can be used in test code without causing breakage due to glibc
>> internals used in headers.
>> 
>> Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
>
>I think it might need some work from the alpha breakage.
>
>> ---
>>  sysdeps/unix/sysv/linux/k_termios.h         | 70 +++++++++++++++++++++
>>  sysdeps/unix/sysv/linux/termios_internals.h | 45 +------------
>>  2 files changed, 71 insertions(+), 44 deletions(-)
>>  create mode 100644 sysdeps/unix/sysv/linux/k_termios.h
>> 
>> diff --git a/sysdeps/unix/sysv/linux/k_termios.h b/sysdeps/unix/sysv/linux/k_termios.h
>> new file mode 100644
>> index 000000000000..99abe7669bd2
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/k_termios.h
>> @@ -0,0 +1,70 @@
>> +/* termios kernel interface for Linux
>> +
>> +   Copyright (C) 1991-2025 Free Software Foundation, Inc.
>> +   This file is part of the GNU C Library.
>> +
>> +   The GNU C Library is free software; you can redistribute it and/or
>> +   modify it under the terms of the GNU Lesser General Public
>> +   License as published by the Free Software Foundation; either
>> +   version 2.1 of the License, or (at your option) any later version.
>> +
>> +   The GNU C Library is distributed in the hope that it will be useful,
>> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> +   Lesser General Public License for more details.
>> +
>> +   You should have received a copy of the GNU Lesser General Public
>> +   License along with the GNU C Library; if not, see
>> +   <https://www.gnu.org/licenses/>.  */
>> +
>> +#ifndef K_TERMIOS_H
>> +#define K_TERMIOS_H
>> +
>> +#include <stddef.h>
>> +#include <unistd.h>
>> +#include <termios.h>
>> +#include <kernel-features.h>
>> +#include <termios_arch.h>
>> +
>> +/* The the termios2 structure used in the kernel interfaces is not the
>> +   same as the termios structure we use in the libc.  Therefore we
>> +   must translate it here.  */
>> +
>> +struct termios2
>> +{
>> +  tcflag_t c_iflag;		/* input mode flags */
>> +  tcflag_t c_oflag;		/* output mode flags */
>> +  tcflag_t c_cflag;		/* control mode flags */
>> +  tcflag_t c_lflag;		/* local mode flags */
>> +#if _HAVE_TERMIOS2_C_CC_BEFORE_C_LINE
>> +  cc_t c_cc[_TERMIOS2_NCCS];	/* control characters */
>> +  cc_t c_line;			/* line discipline */
>> +#else
>> +  cc_t c_line;			/* line discipline */
>> +  cc_t c_cc[_TERMIOS2_NCCS];	/* control characters */
>> +#endif
>> +  speed_t c_ispeed;		/* input speed */
>> +  speed_t c_ospeed;		/* output speed */
>> +};
>> +
>> +/* Alpha got termios2 late, but TCGETS has exactly the same structure
>> +   format and function as TCGETS2. On all other platforms, the termios2
>> +   interface exists as far back as this version of glibc supports.
>> +
>> +   For TCSETS* it is more complicated; this is handled in tcsetattr.c.
>> +
>> +   Some other architectures only have the equivalent of the termios2
>> +   interface, in which case the old ioctl names are the only ones
>> +   presented, but are equivalent to the new ones. */
>> +#ifndef TCGETS2
>> +# define TCGETS2  TCGETS
>> +# define TCSETS2  TCSETS
>> +# define TCSETSW2 TCSETSW
>> +# define TCSETSF2 TCSETSF
>> +#elif !__ASSUME_TERMIOS2
>> +/* Hack for Alpha */
>> +# undef  TCGETS2
>> +# define TCGETS2 TCGETS
>> +#endif
>> +
>> +#endif /* KTERMIOS_H */
>> diff --git a/sysdeps/unix/sysv/linux/termios_internals.h b/sysdeps/unix/sysv/linux/termios_internals.h
>> index e8dbfe74ded5..db12802a35db 100644
>> --- a/sysdeps/unix/sysv/linux/termios_internals.h
>> +++ b/sysdeps/unix/sysv/linux/termios_internals.h
>> @@ -30,50 +30,7 @@
>>  #include <sysdep.h>
>>  #include <shlib-compat.h>
>>  
>> -#include <termios_arch.h>
>> -
>> -/* ---- Kernel interface definitions ---- */
>> -
>> -/* The the termios2 structure used in the kernel interfaces is not the
>> -   same as the termios structure we use in the libc.  Therefore we
>> -   must translate it here.  */
>> -
>> -struct termios2
>> -{
>> -  tcflag_t c_iflag;		/* input mode flags */
>> -  tcflag_t c_oflag;		/* output mode flags */
>> -  tcflag_t c_cflag;		/* control mode flags */
>> -  tcflag_t c_lflag;		/* local mode flags */
>> -#if _HAVE_TERMIOS2_C_CC_BEFORE_C_LINE
>> -  cc_t c_cc[_TERMIOS2_NCCS];	/* control characters */
>> -  cc_t c_line;			/* line discipline */
>> -#else
>> -  cc_t c_line;			/* line discipline */
>> -  cc_t c_cc[_TERMIOS2_NCCS];	/* control characters */
>> -#endif
>> -  speed_t c_ispeed;		/* input speed */
>> -  speed_t c_ospeed;		/* output speed */
>> -};
>> -
>> -/* Alpha got termios2 late, but TCGETS has exactly the same structure
>> -   format and function as TCGETS2. On all other platforms, the termios2
>> -   interface exists as far back as this version of glibc supports.
>> -
>> -   For TCSETS* it is more complicated; this is handled in tcsetattr.c.
>> -
>> -   Some other architectures only have the equivalent of the termios2
>> -   interface, in which case the old ioctl names are the only ones
>> -   presented, but are equivalent to the new ones. */
>> -#ifndef TCGETS2
>> -# define TCGETS2  TCGETS
>> -# define TCSETS2  TCSETS
>> -# define TCSETSW2 TCSETSW
>> -# define TCSETSF2 TCSETSF
>> -#elif !__ASSUME_TERMIOS2
>> -/* Hack for Alpha */
>> -# undef  TCGETS2
>> -# define TCGETS2 TCGETS
>> -#endif
>> +#include <k_termios.h>
>>  
>>  /* ---- Application interface definitions ---- */
>>  
>

Yeah, I need to change the header guard.