Richard Troth wrote:
I would have replied off-list, but I know you have strong spam filtering.
Pieter Harder wrote:
I keep wondering about all this insistence on emulation etc.
There must be something in between the HMC ASCII console (one per LPAR),
and total emulation in software (capable of running thousands)
Then John Summerfield wrote:
_I_ was suggesting a device that VM might emulate (present to Linux as a
virtual keyboard-printer), and that being start/stop. might actually
work well with Linux. I think there is/was an SNA start/stop device too,
but I never programmed any SNA devices, so don't remember them so well.
The 3215 virtual console presented to Linux by z/VM is such a keyboard
printer.
If you connect with a 3270 (or emulator), VM uses fields on the 3270
screen for pre-defined
input and output areas. The guest operating system only sees lines (or
"records")
and the console driver in Linux translates between ASCII and EBCDIC.
I was under the impression that the 3215 is a block-mode device. I note
the channel program in con3215.c attempts to read 160 bytes. It's a bit
hard to see what code's necessary, at another point it's checking that
it doesn't have more than TTY_FLIPBUF_SIZE bytes, and that's defined
elsewhere as 512.
See second in this thread where David says, "I'm not sure there's
anything they *can* do. The guest doesn't see the input until the
attention key gets pressed, so that it really doesn't get control in any
useful way. "
That's why I think it's a block-mode device, and it seems to be handled
as one.
Q. Does it have control and ALT keys?
If there is any flaw with the translation, it is only that Linux should
treat "EBCDIC" as Codepage 1047.
If there is any lack of Unixiness (eg: cannot run 'vi'), it is present
in any "keyboard printer"
whether that is an ASCII animal or a mainframe EBCDIC critter.
On a start-stop device one could usefully run vi in non-visual mode, as
one can use TSO's EDIT command processor. Can you do that?
--
Cheers
John
-- spambait
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