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SubjectRe: [PATCH] tty: Add EXTPROC support for LINEMODE
Ping, any further advice on these issues?

Howard Chu wrote:
> Alan Cox wrote:
>>> diff --git a/arch/alpha/include/asm/termbits.h b/arch/alpha/include/asm/termbits.h
>>> index ad854a4..879dd35 100644
>>> --- a/arch/alpha/include/asm/termbits.h
>>> +++ b/arch/alpha/include/asm/termbits.h
>>> @@ -180,6 +180,7 @@ struct ktermios {
>>> #define FLUSHO 0x00800000
>>> #define PENDIN 0x20000000
>>> #define IEXTEN 0x00000400
>>> +#define EXTPROC 0x10000000
>>
>> For Alpha this value should match OSF if possible.

OSF didn't define this flag, nor did it assign that particular bit to any
purpose. Is that good enough?

>>> + if (cs& TIOCPKT_IOCTL) {
>>> + c = sizeof(struct termios);
>>> + if (c> nr)
>>> + c = nr;
>>> + copy_to_user(b, tty->link->termios, c);
>>> + nr -= c;
>>> + b += c;
>>> + }
>>
>> This is where the wheels come off the bus.
>>
>> The kernel use struct ktermios which is what tty->link->termios is
>>
>> The C library presents this via struct termios which is a glibc invention
>> dependant on the C library and which is converted by libc from struct
>> termios or struct termios2 depending on your C library
>>
>> How you fix that given a broken by design historic Unix interface which
>> pastes arbitary struct termios objects into the data stream is an
>> interesting question - doubly so when like most Unixen we have also have
>> extended terminal attributes as well (termiox)
>
> Are you suggesting that this is completely unfixable/unworkable? Would it be
> sufficient to use kernel_termios_to_user_termios() ?
>
Actually using kernel_termios_to_user_termios_1(). In all supported
architectures this structure is basically aligned with but smaller than the
userland struct termios. As such it will leave any unused fields unwritten in
the user struct. This usually means it will leave c_ispeed and c_ospeed unset
in the user struct, but that's a don't-care anyway since we're only talking
about ptys here, and changing the speed (besides setting it to zero) is
irrelevant for ptys.

--
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/


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