drivers/spi: Properly check for rx/tx and buffering on

[tbursztyka]

Current buffers might be configured to skip data, thus only len will be
set, buf will be NULL. Buffer should be used if only len is > 0 and
buffer is valid as well.

tx/rx are "on" if len is > 0
tx/rx buf should be touched if only len is > 0 and buf != NULL.

Signed-off-by: Tomasz Bursztyka tomasz.bursztyka@linux.intel.com

[codecov-io]

Codecov Report

Merging #5785 into master will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5785      +/-   ##
==========================================
- Coverage   54.37%   54.32%   -0.06%     
==========================================
  Files         457      457              
  Lines       43298    43298              
  Branches     8302     8302              
==========================================
- Hits        23545    23521      -24     
- Misses      19612    19638      +26     
+ Partials      141      139       -2

Impacted Files	Coverage Δ
...sts/net/ieee802154/l2/src/ieee802154_fake_driver.c	74.35% <0%> (-15.39%)	⬇️
include/net/net_ip.h	67.36% <0%> (-4.87%)	⬇️
subsys/net/ip/6lo.c	38.73% <0%> (-2.79%)	⬇️
arch/posix/core/posix_core.c	85.34% <0%> (-1.73%)	⬇️
arch/posix/soc/inf_clock/soc.c	66.66% <0%> (+3.33%)	⬆️

---

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[ydamigos]

LGTM

[nzmichaelh]

Hi @tbursztyka this might break the stm32 driver. Inside the shift-next-byte loop, the stm32 does the following:

data = read byte
if spi_context_rx_on(...) {
   *ctx.rx_buf = data
   spi_context_update_rx(...)
}

With this change, the above code will fail when rx_buf.buf = NULL and rx_buf.len > 0.

WDYT about documenting the spi_context API then we can go through and fix the current users?

[ydamigos]

I have already pushed a commit to fix it in PR #5413.

[nzmichaelh]

Ack