For FAT the same buffer is used for read and writes, there
is a possibility a cache line is dirty. But the fs is
not dirty and will not write the sector to disk. This can
be seen https://github.com/PX4/NuttX/pull/175
When the system is busy that cache line can be evicted after the
RX DMA has completed and overwrite the data in memory. The solution
is to invalidate before the DMA to prevent an evection causing an
overwite, and after the DMA it to insure coherency.
This pull request improves the dependencies for Makefile.unix::context rule.
* `include/math.h`, `include/float.h`, `include/stdarg.h`, `include/setjmp.h` are only added to `context`'s dependency if the Kconfig value is set. This prevents `context` from trying to make `include/math.h` only to find out there's no command to create the file.
* Instead of executing $(CONTEXTDIRS) in a for loop in the `context` rule, $(CONTEXTDIRS) are added as a dependency to `context` and a rule is created to create the targets. Real files are used, to prevent needlessly rebuilding the same `context` over and over and over again.
* Instead of making the directory `staging`, add it as an order-only dependency for `context`. this ensures the directory is only created if it doesn't exist.
Tested by running:
```
(cd tools && ./configure.sh -a ../incubator-nuttx-apps stm32f3discovery:nsh)
make context
```
First time running context:
```
➜ incubator-nuttx git:(improve-make-context) time make context
make[1]: Entering directory '/home/user/code/fitbit/incubator-nuttx/tools'
make[1]: Leaving directory '/home/user/code/fitbit/incubator-nuttx/tools'
make[1]: Entering directory '/home/user/code/fitbit/incubator-nuttx'
make[2]: Entering directory '/home/user/code/fitbit/incubator-nuttx/boards'
make[2]: Leaving directory '/home/user/code/fitbit/incubator-nuttx/boards'
make[2]: Entering directory '/home/user/code/fitbit/incubator-nuttx-apps'
make[3]: Entering directory '/home/user/code/fitbit/incubator-nuttx-apps/platform'
make[3]: Leaving directory '/home/user/code/fitbit/incubator-nuttx-apps/platform'
make[3]: Entering directory '/home/user/code/fitbit/incubator-nuttx-apps/builtin'
make[3]: Leaving directory '/home/user/code/fitbit/incubator-nuttx-apps/builtin'
make[2]: Leaving directory '/home/user/code/fitbit/incubator-nuttx-apps'
make[2]: Entering directory '/home/user/code/fitbit/incubator-nuttx/graphics'
make[3]: Entering directory '/home/user/code/fitbit/incubator-nuttx/graphics/nxglib'
make[3]: Leaving directory '/home/user/code/fitbit/incubator-nuttx/graphics/nxglib'
make[3]: Entering directory '/home/user/code/fitbit/incubator-nuttx/graphics/nxglib'
make[3]: Leaving directory '/home/user/code/fitbit/incubator-nuttx/graphics/nxglib'
make[3]: Entering directory '/home/user/code/fitbit/incubator-nuttx/graphics/nxglib'
make[3]: Leaving directory '/home/user/code/fitbit/incubator-nuttx/graphics/nxglib'
make[2]: Leaving directory '/home/user/code/fitbit/incubator-nuttx/graphics'
make[1]: Leaving directory '/home/user/code/fitbit/incubator-nuttx'
Create .version
make[1]: Entering directory '/home/user/code/fitbit/incubator-nuttx/tools'
make[1]: Leaving directory '/home/user/code/fitbit/incubator-nuttx/tools'
Create version.h
LN: include/arch to arch/arm/include
LN: include/arch/board to /home/user/code/fitbit/incubator-nuttx/boards/arm/stm32/stm32f3discovery/include
LN: include/arch/chip to arch/arm/include/stm32
LN: arch/arm/src/board to /home/user/code/fitbit/incubator-nuttx/boards/arm/stm32/stm32f3discovery/../common
LN: arch/arm/src/board/board to /home/user/code/fitbit/incubator-nuttx/boards/arm/stm32/stm32f3discovery/src
LN: arch/arm/src/chip to arch/arm/src/stm32
LN: /home/user/code/fitbit/incubator-nuttx/drivers/platform to /home/user/code/fitbit/incubator-nuttx/drivers/dummy
make[1]: Entering directory '/home/user/code/fitbit/incubator-nuttx/boards'
make[1]: Leaving directory '/home/user/code/fitbit/incubator-nuttx/boards'
make[1]: Entering directory '/home/user/code/fitbit/incubator-nuttx-apps'
make[2]: Entering directory '/home/user/code/fitbit/incubator-nuttx-apps/platform'
LN: platform/board to /home/user/code/fitbit/incubator-nuttx-apps/platform/dummy
make[2]: Leaving directory '/home/user/code/fitbit/incubator-nuttx-apps/platform'
make[1]: Leaving directory '/home/user/code/fitbit/incubator-nuttx-apps'
make context 0.95s user 0.45s system 109% cpu 1.281 total
```
second time running context:
```
➜ incubator-nuttx git:(improve-make-context) time make context
Create .version
Create version.h
LN: include/arch/board to /home/user/code/fitbit/incubator-nuttx/boards/arm/stm32/stm32f3discovery/include
make[1]: Entering directory '/home/user/code/fitbit/incubator-nuttx/boards'
make[1]: Nothing to be done for 'dirlinks'.
make[1]: Leaving directory '/home/user/code/fitbit/incubator-nuttx/boards'
make[1]: Entering directory '/home/user/code/fitbit/incubator-nuttx-apps'
make[2]: Entering directory '/home/user/code/fitbit/incubator-nuttx-apps/platform'
LN: platform/board to /home/user/code/fitbit/incubator-nuttx-apps/platform/dummy
make[2]: Leaving directory '/home/user/code/fitbit/incubator-nuttx-apps/platform'
make[1]: Leaving directory '/home/user/code/fitbit/incubator-nuttx-apps'
make context 0.30s user 0.20s system 121% cpu 0.414 total
```
According to Make documentation:
- "Commas and unmatched parentheses or braces cannot appear in the text
of an argument as written";
- "Leading spaces cannot appear in the text of the first argument as
written".
Although in the current state it was not resulting in parsing issues, it
is better to fix it.
Signed-off-by: Gustavo Henrique Nihei <gustavo.nihei@espressif.com>
