linux-kernel - Re: [PATCH] i2c: iproc: Change driver to use 'BIT' macro

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Date:   Fri, 12 Apr 2019 22:59:40 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Ray Jui <ray.jui@...adcom.com>, Wolfram Sang <wsa@...-dreams.de>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bcm-kernel-feedback-list@...adcom.com" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Rayagonda Kokatanur <rayagonda.kokatanur@...adcom.com>
Subject: Re: [PATCH] i2c: iproc: Change driver to use 'BIT' macro

On 2019-04-03 23:05, Ray Jui wrote:
> Change the iProc I2C driver to use the 'BIT' macro from all '1 << XXX'
> bit operations to get rid of compiler warning and improve readability of
> the code

All? I see lots more '1 << XXX_SHIFT' matches. I might be behind though?
Anyway, if you are cleaning up, I'm just flagging that BIT(XXX_SHIFT) looks
a bit clunky to me. You might consider renaming all those single-bit
XXX_SHIFT macros to simple be

#define XXX BIT(<xxx>)

instead of

#define XXX_SHIFT <xxx>

but that triggers more churn, so is obviously more error prone. You might
not dare it?

Cheers,
Peter

> Signed-off-by: Ray Jui <ray.jui@...adcom.com>
> ---
>  drivers/i2c/busses/i2c-bcm-iproc.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
> index 562942d0c05c..a845b8decac8 100644
> --- a/drivers/i2c/busses/i2c-bcm-iproc.c
> +++ b/drivers/i2c/busses/i2c-bcm-iproc.c
> @@ -717,7 +717,7 @@ static int bcm_iproc_i2c_xfer_single_msg(struct bcm_iproc_i2c_dev *iproc_i2c,
>  
>  			/* mark the last byte */
>  			if (i == msg->len - 1)
> -				val |= 1 << M_TX_WR_STATUS_SHIFT;
> +				val |= BIT(M_TX_WR_STATUS_SHIFT);
>  
>  			iproc_i2c_wr_reg(iproc_i2c, M_TX_OFFSET, val);
>  		}
> @@ -844,7 +844,7 @@ static int bcm_iproc_i2c_cfg_speed(struct bcm_iproc_i2c_dev *iproc_i2c)
>  
>  	iproc_i2c->bus_speed = bus_speed;
>  	val = iproc_i2c_rd_reg(iproc_i2c, TIM_CFG_OFFSET);
> -	val &= ~(1 << TIM_CFG_MODE_400_SHIFT);
> +	val &= ~BIT(TIM_CFG_MODE_400_SHIFT);
>  	val |= (bus_speed == 400000) << TIM_CFG_MODE_400_SHIFT;
>  	iproc_i2c_wr_reg(iproc_i2c, TIM_CFG_OFFSET, val);
>  
> @@ -995,7 +995,7 @@ static int bcm_iproc_i2c_resume(struct device *dev)
>  
>  	/* configure to the desired bus speed */
>  	val = iproc_i2c_rd_reg(iproc_i2c, TIM_CFG_OFFSET);
> -	val &= ~(1 << TIM_CFG_MODE_400_SHIFT);
> +	val &= ~BIT(TIM_CFG_MODE_400_SHIFT);
>  	val |= (iproc_i2c->bus_speed == 400000) << TIM_CFG_MODE_400_SHIFT;
>  	iproc_i2c_wr_reg(iproc_i2c, TIM_CFG_OFFSET, val);
>  
>