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Add support for accessing printf, sprintf, puts, etc. strings that do not lie in the MCU data space

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3738 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo 2011-07-01 19:08:04 +00:00
parent ab2ebc3e73
commit f69f1e709d
1 changed files with 29 additions and 5 deletions
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34
configs/README.txt
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@ -489,15 +489,39 @@ defconfig -- This is a configuration file similar to the Linux
The architecture can provide optimized versions of the
following to improve system performance
CONFIG_ARCH_MEMCPY, CONFIG_ARCH_MEMCMP, CONFIG_ARCH_MEMMOVE
CONFIG_ARCH_MEMSET, CONFIG_ARCH_STRCMP, CONFIG_ARCH_STRCPY
CONFIG_ARCH_STRNCPY, CONFIG_ARCH_STRLEN, CONFIG_ARCH_STRNLEN
CONFIG_ARCH_BZERO
CONFIG_ARCH_MEMCPY, CONFIG_ARCH_MEMCMP, CONFIG_ARCH_MEMMOVE
CONFIG_ARCH_MEMSET, CONFIG_ARCH_STRCMP, CONFIG_ARCH_STRCPY
CONFIG_ARCH_STRNCPY, CONFIG_ARCH_STRLEN, CONFIG_ARCH_STRNLEN
CONFIG_ARCH_BZERO
The architecture may provide custom versions of certain
standard header files:
CONFIG_ARCH_MATH_H, CONFIG_ARCH_STDBOOL_H, CONFIG_ARCH_STDINT_H
CONFIG_ARCH_MATH_H, CONFIG_ARCH_STDBOOL_H, CONFIG_ARCH_STDINT_H
CONFIG_ARCH_ROMGETC - In Harvard architectures, data accesses and
instruction accesses occur on different busses, perhaps
concurrently. All data accesses are performed on the data bus
unless special machine instructions are used to read data
from the instruction address space. Also, in the typical
MCU, the available SRAM data memory is much smaller that the
non-volatile FLASH instruction memory. So if the application
requires many constant strings, the only practical solution may
be to store those constant strings in FLASH memory where they
can only be accessed using architecture-specific machine
instructions.
If CONFIG_ARCH_ROMGETC is defined, then the architecture logic
must export the function up_romgetc(). up_romgetc() will simply
read one byte of data from the instruction space.
If CONFIG_ARCH_ROMGETC, certain C stdio functions are effected:
(1) All format strings in printf, fprintf, sprintf, etc. are
assumed to lie in FLASH (string arguments for %s are still assumed
to reside in SRAM). And (2), the string argument to puts and fputs
is assumed to reside in FLASH. Clearly, these assumptions may have
to modified for the particular needs of your environment. There
is no "one-size-fits-all" solution for this problem.
Sizes of configurable things (0 disables)