linux-kernel - Re: [RFC] staging: vt6656: Add formula to the vnt_rf

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Date:   Tue, 14 Apr 2020 16:12:14 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Oscar Carter <oscar.carter@....com>
Cc:     Forest Bond <forest@...ttletooquiet.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Malcolm Priestley <tvboxspy@...il.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] staging: vt6656: Add formula to the vnt_rf_addpower
 function

On Mon, Apr 13, 2020 at 04:02:09PM +0200, Oscar Carter wrote:
> diff --git a/drivers/staging/vt6656/rf.c b/drivers/staging/vt6656/rf.c
> index 4f9aba0f21b0..3b200d7290a5 100644
> --- a/drivers/staging/vt6656/rf.c
> +++ b/drivers/staging/vt6656/rf.c
> @@ -575,28 +575,14 @@ int vnt_rf_setpower(struct vnt_private *priv, u32 rate, u32 channel)
> 
>  static u8 vnt_rf_addpower(struct vnt_private *priv)
>  {
> +	s32 base;

Just use "int".  s32 is for when signed 32 bit is specified in the
hardware.  I realize that it's done in this file, but if all your
friends jumped off a bridge doesn't mean you should drink their kool-aid.

>  	s32 rssi = -priv->current_rssi;
> 
>  	if (!rssi)
>  		return 7;
> 
> -	if (priv->rf_type == RF_VT3226D0) {
> -		if (rssi < -70)
> -			return 9;
> -		else if (rssi < -65)
> -			return 7;
> -		else if (rssi < -60)
> -			return 5;
> -	} else {
> -		if (rssi < -80)
> -			return 9;
> -		else if (rssi < -75)
> -			return 7;
> -		else if (rssi < -70)
> -			return 5;
> -	}
> -
> -	return 0;
> +	base = (priv->rf_type == RF_VT3226D0) ? -60 : -70;
> +	return (rssi < base--) ? ((rssi - base) / -5) * 2 + 5 : 0;
                       ^^^^^^
I quite hate this postop.  It would have been cleaner to write it like:

	return (rssi < base) ? ((rssi - (base - 1)) / -5) * 2 + 5 : 0

I'm sorry, I'm not clever enough to figure out the potential values of
"rssi".  How did you work out this formula?  It feels like it came from
a standard or something?  Do we not have a function already which
implements the standard?

regards,
dan carpenter