FreeCalypso > hg > freecalypso-tools

annotate target-utils/libprintf/README @ 619:f82551c77e58

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libserial-newlnx: ASYNC_LOW_LATENCY patch reverted Reports from Das Signal indicate that loadtools performance on Debian is about the same as on Slackware, and that including or omitting the ASYNC_LOW_LATENCY patch from Serg makes no difference. Because the patch in question does not appear to be necessary, it is being reverted until and unless someone other than Serg reports an actual real-world system on which loadtools operation times are slowed compared to the Mother's Slackware reference and on which Slackware-like performance can be restored by setting the ASYNC_LOW_LATENCY flag.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 27 Feb 2020 01:09:48 +0000
parents e7502631a0f9
children
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e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
parents:
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1 The present libprintf is a very light printf implementation that is well-suited
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
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2 for simple bare-metal programs like loadagent; in the present case it overrides
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
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3 the much heavier printf implementation in newlib. Programs like the present
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
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4 loadagent only need printf in order to scribble on the serial console port,
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
parents:
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5 and the most sensible implementation is to have the "character output" function
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
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6 from the guts of printf point directly to the physical UART output routine, or
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
parents:
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7 a trivial wrapper that turns \n into \r\n. In contrast, newlib's version would
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
parents:
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8 pull in the complete FILE table infrastructure and malloc etc - maybe OK for
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
parents:
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9 more complex embedded programs that use those facilities for other things under
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
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10 a bona fide RTOS, but it would be disgusting to pull that stuff in for a
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
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11 minimal program like ours.
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Mychaela Falconia <falcon@freecalypso.org>
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Mychaela Falconia <falcon@freecalypso.org>
parents:
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13 The present printf implementation has been used earlier by the same author
e7502631a0f9 initial import from freecalypso-sw rev 1033:5ab737ac3ad7
Mychaela Falconia <falcon@freecalypso.org>
parents:
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14 (Michael Spacefalcon) in the StarMON family of PowerPC bootloaders, and in my
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parents:
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15 MC68x302-based SDSL CPE devices (Hack-o-Rocket and OSDCU).