Re: [PATCH 4/8] staging: pi433: add parentheses to mask and shift

[Marcus Wolf]

Am 13.12.2017 um 16:21 schrieb Valentin Vidic:
> Fixes checkpatch warning:
>
>    WARNING: Possible precedence defect with mask then right shift - may need parentheses
>
> Signed-off-by: Valentin Vidic <Valentin.Vidic@xxxxxxxxx>
> ---
>   drivers/staging/pi433/rf69.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/pi433/rf69.c b/drivers/staging/pi433/rf69.c
> index f77ecd60f43a..b1e243e5bcac 100644
> --- a/drivers/staging/pi433/rf69.c
> +++ b/drivers/staging/pi433/rf69.c
> @@ -102,7 +102,7 @@ enum modulation rf69_get_modulation(struct spi_device *spi)
>   
>   	currentValue = rf69_read_reg(spi, REG_DATAMODUL);
>   
> -	switch (currentValue & MASK_DATAMODUL_MODULATION_TYPE >> 3) { // TODO improvement: change 3 to define
> +	switch ((currentValue & MASK_DATAMODUL_MODULATION_TYPE) >> 3) { // TODO improvement: change 3 to define

As mentioned by Dan, this change isn't needed any more, since ther was a 
bug, that's already fixed.

>   	case DATAMODUL_MODULATION_TYPE_OOK: return OOK;
>   	case DATAMODUL_MODULATION_TYPE_FSK: return FSK;
>   	default:			    return UNDEF;
> @@ -340,7 +340,7 @@ enum lnaGain rf69_get_lna_gain(struct spi_device *spi)
>   
>   	currentValue = rf69_read_reg(spi, REG_LNA);
>   
> -	switch (currentValue & MASK_LNA_CURRENT_GAIN >> 3) { // improvement: change 3 to define
> +	switch ((currentValue & MASK_LNA_CURRENT_GAIN) >> 3) { // improvement: change 3 to define

To my knowledge,'>>' is stronger than '&'.
So this change will modify the behaviour.
If I am wrong, the code was wrong from the beginning.

What should happen here, is:
read the value from reg and do a bitwise and with the shifted value from 
MASK_...

>   	case LNA_GAIN_AUTO:	    return automatic;
>   	case LNA_GAIN_MAX:	    return max;
>   	case LNA_GAIN_MAX_MINUS_6:  return maxMinus6;

--
Smarthome-Wolf UG (haftungsbeschrÃnkt)
Helene-Lange-Weg 23
80637 MÃnchen
Amtsgericht MÃnchen, HRB 223529
Umastzsteuer-ID: DE304719911
GeschÃftsfÃhrer: Marcus Wolf