linux-kernel - Re: [PATCH 6/8 v2] staging: pi433: use defines for shifting register values

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Date:   Wed, 13 Dec 2017 19:15:09 +0200
From:   Marcus Wolf <marcus.wolf@...rthome-wolf.de>
To:     Valentin Vidic <Valentin.Vidic@...Net.hr>
Cc:     Simon Sandström <simon@...anor.nu>,
        Marcin Ciupak <marcin.s.ciupak@...il.com>,
        Marcus Wolf <linux@...f-entwicklungen.de>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 6/8 v2] staging: pi433: use defines for shifting register
 values



Am 13.12.2017 um 18:55 schrieb Valentin Vidic:
> Avoid shifting by magic numbers and use defines instead.
> 
> Signed-off-by: Valentin Vidic <Valentin.Vidic@...Net.hr>
> ---
> v2: - drop change for SHIFT_DATAMODUL_MODULATION_TYPE
>      - move shifting to the header file
> 
>   drivers/staging/pi433/rf69.c           | 16 ++++++++--------
>   drivers/staging/pi433/rf69_registers.h |  8 ++++++++
>   2 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/staging/pi433/rf69.c b/drivers/staging/pi433/rf69.c
> index f77ecd60f43a..ce259b4f0b0e 100644
> --- a/drivers/staging/pi433/rf69.c
> +++ b/drivers/staging/pi433/rf69.c
> @@ -340,14 +340,14 @@ 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
> -	case LNA_GAIN_AUTO:	    return automatic;
> -	case LNA_GAIN_MAX:	    return max;
> -	case LNA_GAIN_MAX_MINUS_6:  return maxMinus6;
> -	case LNA_GAIN_MAX_MINUS_12: return maxMinus12;
> -	case LNA_GAIN_MAX_MINUS_24: return maxMinus24;
> -	case LNA_GAIN_MAX_MINUS_36: return maxMinus36;
> -	case LNA_GAIN_MAX_MINUS_48: return maxMinus48;
> +	switch (currentValue & MASK_LNA_CURRENT_GAIN) {
> +	case LNA_GAIN_AUTO_SHIFTED:	    return automatic;
> +	case LNA_GAIN_MAX_SHIFTED:	    return max;
> +	case LNA_GAIN_MAX_MINUS_6_SHIFTED:  return maxMinus6;
> +	case LNA_GAIN_MAX_MINUS_12_SHIFTED: return maxMinus12;
> +	case LNA_GAIN_MAX_MINUS_24_SHIFTED: return maxMinus24;
> +	case LNA_GAIN_MAX_MINUS_36_SHIFTED: return maxMinus36;
> +	case LNA_GAIN_MAX_MINUS_48_SHIFTED: return maxMinus48;
>   	default:		    return undefined;
>   	}
>   }
> diff --git a/drivers/staging/pi433/rf69_registers.h b/drivers/staging/pi433/rf69_registers.h
> index d23b8b668ef5..6329bbf9e499 100644
> --- a/drivers/staging/pi433/rf69_registers.h
> +++ b/drivers/staging/pi433/rf69_registers.h
> @@ -237,6 +237,7 @@
>   #define  MASK_LNA_ZIN				0x80
>   #define  MASK_LNA_CURRENT_GAIN			0x38
>   #define  MASK_LNA_GAIN				0x07
> +#define  SHIFT_LNA_CURRENT_GAIN			3
>   
>   #define  LNA_GAIN_AUTO				0x00 /* default */
>   #define  LNA_GAIN_MAX				0x01
> @@ -246,6 +247,13 @@
>   #define  LNA_GAIN_MAX_MINUS_36			0x05
>   #define  LNA_GAIN_MAX_MINUS_48			0x06
>   
> +#define  LNA_GAIN_AUTO_SHIFTED			(LNA_GAIN_AUTO		<< SHIFT_LNA_CURRENT_GAIN)
> +#define  LNA_GAIN_MAX_SHIFTED			(LNA_GAIN_MAX		<< SHIFT_LNA_CURRENT_GAIN)
> +#define  LNA_GAIN_MAX_MINUS_6_SHIFTED		(LNA_GAIN_MAX_MINUS_6	<< SHIFT_LNA_CURRENT_GAIN)
> +#define  LNA_GAIN_MAX_MINUS_12_SHIFTED		(LNA_GAIN_MAX_MINUS_12	<< SHIFT_LNA_CURRENT_GAIN)
> +#define  LNA_GAIN_MAX_MINUS_24_SHIFTED		(LNA_GAIN_MAX_MINUS_24	<< SHIFT_LNA_CURRENT_GAIN)
> +#define  LNA_GAIN_MAX_MINUS_36_SHIFTED		(LNA_GAIN_MAX_MINUS_36	<< SHIFT_LNA_CURRENT_GAIN)
> +#define  LNA_GAIN_MAX_MINUS_48_SHIFTED		(LNA_GAIN_MAX_MINUS_48	<< SHIFT_LNA_CURRENT_GAIN)
>   
>   /* RegRxBw (0x19) and RegAfcBw (0x1A) */
>   #define  MASK_BW_DCC_FREQ			0xE0
> 

Hi Valentin,

nice :-)

Name is a bit strange, since it's not really shifted. If you have a look 
at the datasheet (RegLNA, page 68), there are two sections "by chance" 
both using the max, -6, -12 ...
But auto is not needed for current gain (was already bad in my old 
implementation!), since the current gain will always report a real 
value, never auto.
So maybe it is a little(!) better not to derive the "current" defines 
from the "select" defines and use names like LNA_GAIN_MAX_SELECT and 
LNA_GAIN_MAX_CURRENT.

Never the less - I like patch 6/8 v2 a lot more, than the original one :-)

Thank you very much for your help,

Marcus