linux-kernel - Re: staging: pi433: Possible bug in rf69.c

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Date:   Sat, 11 Nov 2017 18:40:02 +0200
From:   Marcus Wolf <marcus.wolf@...rthome-wolf.de>
To:     Joe Perches <joe@...ches.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        dan.carpenter@...cle.com
Subject: Re: staging: pi433: Possible bug in rf69.c

Hi Joe,

thank you for your suggestion.

The enums are necessary for the (old fashioned) ioctl interface, too.
So the user space uses these enums in order to configure the driver.
If we want to completely remove rf69_enum.h, we need to find a solution
for that, too.

 From the optics/readability, I like your idea with the Macro for the cases.

On the other hand, I have already prepared a patch, that uses setbit, 
resetbit
and readmodifywrite inline fuctions instead of the macros WRITE_REG, ...
That was an idea of Walter Harms in order to increase readability and
reduce macros, because Walter prefers inline functions to macros.

As discussed with Greg, I will provide the patch, as soon as 4.15rc1 is out.
Maybe we should move the discussion to then, so you can have a look to that?

Cheers,

Marcus


Am 11.11.2017 um 18:02 schrieb Joe Perches:
> On Fri, 2017-11-10 at 18:23 +0100, Marcus Wolf wrote:
>> Hi everybody!
>>
>> Just comparing the master of Gregs statging of pi433 with my local SVN
>> to review all changes, that were done the last monthes.
>>
>> I am not sure, but maybe we imported a bug in rf69.c lines 378 and
>> following:
>>
>> Gregs repo:
>> 	case automatic:	 return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) & LNA_GAIN_AUTO) );
>> 	case max:	 return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) & LNA_GAIN_MAX) );
>> 	case maxMinus6:  return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) & LNA_GAIN_MAX_MINUS_6) );
>> 	case maxMinus12: return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) & LNA_GAIN_MAX_MINUS_12) );
>> 	case maxMinus24: return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) & LNA_GAIN_MAX_MINUS_24) );
>> 	case maxMinus36: return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) & LNA_GAIN_MAX_MINUS_36) );
>> 	case maxMinus48: return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) & LNA_GAIN_MAX_MINUS_48) );
>>
>> my repo:
>> 	case automatic:	 return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) | LNA_GAIN_AUTO) );
>> 	case max:	 return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) | LNA_GAIN_MAX) );
>> 	case maxMinus6:  return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) | LNA_GAIN_MAX_MINUS_6) );
>> 	case maxMinus12: return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) | LNA_GAIN_MAX_MINUS_12) );
>> 	case maxMinus24: return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) | LNA_GAIN_MAX_MINUS_24) );
>> 	case maxMinus36: return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) | LNA_GAIN_MAX_MINUS_36) );
>> 	case maxMinus48: return WRITE_REG(REG_LNA, ( (READ_REG(REG_LNA) &
>> ~MASK_LNA_GAIN) | LNA_GAIN_MAX_MINUS_48) );
>>
>> Up to my opinion, my (old) version is better then Gregs (new) version.
>> If you agree, I'll prepare a patch, to revert the modification.
> 
> There seems to be a lot of enum/#define duplication in this driver.
> 
> For instance:
> 
> drivers/staging/pi433/rf69_registers.h
> 
> #define  LNA_GAIN_AUTO				0x00 /* default */
> #define  LNA_GAIN_MAX				0x01
> #define  LNA_GA
> IN_MAX_MINUS_6			0x02
> #define  LNA_GAIN_MAX_MINUS_12
> 			0x03
> #define  LNA_GAIN_MAX_MINUS_24		
> 	0x04
> #define  LNA_GAIN_MAX_MINUS_36			0x05
> #d
> efine  LNA_GAIN_MAX_MINUS_48			0x06
> 
> vs
> 
> drivers/staging/pi433/rf69_enum.h
> 
> enum lnaGain
> {
>      automatic,
>      max,
>      maxMinus6,
>      maxMinus12,
>      maxM
> inus24,
>      maxMinus36,
>      maxMinus48,
>      undefined
> };
> 
> My suggestion would be to remove drivers/staging/pi433/rf69_enum.h
> where possible and convert all these switch/case entries into
> macros like
> 
> #define GAIN_CASE(type)						\
> 	case type: return WRITE_REG(REG_LNA,			\
> 				    (READ_REG(REG_LNA) & ~MASK_LNA_GAIN) | (type));
> 
> so for example this switch becomes
> 
> 	switch (lnaGain) {
> 	GAIN_CASE(LNA_GAIN_AUTO);
> 	...
> 	}
>