On Thu, Jul 23, 2020 at 11:09:40AM +0200, Arnd Bergmann wrote:

On Thu, Jul 23, 2020 at 9:39 AM Krzysztof Kozlowski [off-list ref] wrote:

quoted

do-while is a preferred way for complex macros because of safety
reasons.  This fixes checkpatch error:

    ERROR: Macros starting with if should be enclosed by a do - while
        loop to avoid possible if/else logic defects

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

This is an improvement, but the macro still has other issues that
are just as bad as the one you address:

- Using the # operator to avoid the "" in the invocation seems confusing

I guess it was useful for debugging.

- it implicitly uses the 'cs' and 't' variables of the calling function instead
  of passing them as arguments.

Actually another reason to convert it to just a function.

- it calls 'return -1' in a function that otherwise uses errno-style
  return codes, so this gets interpreted as EPERM "Operation not
  permitted".

The users of this macro also do it (gpmc_cs_set_timings()) so this
wrong practice is consistent with the driver. :)

I would probably just open-code the entire thing and remove the
macro like:

ret = 0;
ret |= set_gpmc_timing_reg(cs, GPMC_CS_CONFIG2,  0,  3, 0, t->cs_on,
GPMC_CD_FCLK, "cs_on");
ret |= set_gpmc_timing_reg(cs, GPMC_CS_CONFIG2,  8,  12, 0,
t->cs_rd_off, GPMC_CD_FCLK, "cs_rd_off");
ret |= set_gpmc_timing_reg(cs, GPMC_CS_CONFIG2,  16,  20, 0,
t->cs_wr_off, GPMC_CD_FCLK, "cs_wr_off);
...
if (ret)
     return -ENXIO;a

I like this approach because it also removes the 'return' from macro
which is not desired.

Of maybe leave the macro, but remove the if/return part and use
the "ret |= GPMC_SET_ONE(...)" trick to avoid some of the problems.

I could probably then keep it as a function.  This would be the safest
and remove most of the problems here.

Best regards,
Krzysztof


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