s390/tty3270: convert lines during output

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The length of the screen line is variable with the 3270 protocol.
For each attribute (foreground, background color, highlighting etc)
we need 3 bytes: the set attribute order, the attribute number, and
the value of the attribute. This means that depending on screen content,
we might end up 3*3 bytes addtional data for a single character.

Allocating the maximum possible amount of memory is quite a lot, and
we cannot easily extend the lines by allocating memory because we
might get called from atomic context. Failing to extend the memory
would also be bad as that would mean that we could miss kernel messages
in oom conditions. Therefore move the conversion to a 3270 datastream
to tty3270_update(), and use only single line buffer.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

...

This commit is contained in:

Sven Schnelle 2022-11-24 22:53:44 +01:00 • committed by Heiko Carstens

parent ec1b0a33a3

commit 9c138af9b7

2 changed files with 102 additions and 238 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

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338

drivers/s390/char/con3270.c

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2

drivers/s390/char/raw3270.h

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