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From: Andi Shyti <andi.shyti@kernel.org>
To: carlos.song@nxp.com
Cc: aisheng.dong@nxp.com, shawnguo@kernel.org,
	s.hauer@pengutronix.de, kernel@pengutronix.de,
	festevam@gmail.com, xiaoning.wang@nxp.com, haibo.chen@nxp.com,
	linux-imx@nxp.com, linux-i2c@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i2c: imx-lpi2c: fix type char overflow issue when calculating the clock cycle
Date: Tue, 30 May 2023 20:50:36 +0200	[thread overview]
Message-ID: <20230530185036.ggep3pv7booqtb6b@intel.intel> (raw)
In-Reply-To: <20230529080251.3614380-1-carlos.song@nxp.com>

On Mon, May 29, 2023 at 04:02:51PM +0800, carlos.song@nxp.com wrote:
> From: Clark Wang <xiaoning.wang@nxp.com>
> 
> Claim clkhi and clklo as integer type to avoid possible calculation
> errors caused by data overflow.
> 
> Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
> Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
> Signed-off-by: Carlos Song <carlos.song@nxp.com>
> ---
>  drivers/i2c/busses/i2c-imx-lpi2c.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
> index 40a4420d4c12..7dd33564cbe1 100644
> --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> @@ -211,8 +211,8 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct *lpi2c_imx)
>  /* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
>  static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
>  {
> -	u8 prescale, filt, sethold, clkhi, clklo, datavd;
> -	unsigned int clk_rate, clk_cycle;
> +	u8 prescale, filt, sethold, datavd;
> +	unsigned int clk_rate, clk_cycle, clkhi, clklo;

looks OK.

Reviewed-by: Andi Shyti <andi.shyti@kernel.org> 

there is, though, another part I would take care of, this bit:

	clklo = clk_cycle - clkhi;
	if (clklo < 64)
		break;

It might be unlikely, but if "clk_cycle > clkhi" then all the
calculation. Do you mind adding a check:

	if (unlikely(clk_cycle > clkhi))
		break;

Andi

>  	enum lpi2c_imx_pincfg pincfg;
>  	unsigned int temp;
>  
> -- 
> 2.34.1
> 

WARNING: multiple messages have this Message-ID (diff)
From: Andi Shyti <andi.shyti@kernel.org>
To: carlos.song@nxp.com
Cc: aisheng.dong@nxp.com, shawnguo@kernel.org,
	s.hauer@pengutronix.de, kernel@pengutronix.de,
	festevam@gmail.com, xiaoning.wang@nxp.com, haibo.chen@nxp.com,
	linux-imx@nxp.com, linux-i2c@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i2c: imx-lpi2c: fix type char overflow issue when calculating the clock cycle
Date: Tue, 30 May 2023 20:50:36 +0200	[thread overview]
Message-ID: <20230530185036.ggep3pv7booqtb6b@intel.intel> (raw)
In-Reply-To: <20230529080251.3614380-1-carlos.song@nxp.com>

On Mon, May 29, 2023 at 04:02:51PM +0800, carlos.song@nxp.com wrote:
> From: Clark Wang <xiaoning.wang@nxp.com>
> 
> Claim clkhi and clklo as integer type to avoid possible calculation
> errors caused by data overflow.
> 
> Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
> Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
> Signed-off-by: Carlos Song <carlos.song@nxp.com>
> ---
>  drivers/i2c/busses/i2c-imx-lpi2c.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
> index 40a4420d4c12..7dd33564cbe1 100644
> --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> @@ -211,8 +211,8 @@ static void lpi2c_imx_stop(struct lpi2c_imx_struct *lpi2c_imx)
>  /* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
>  static int lpi2c_imx_config(struct lpi2c_imx_struct *lpi2c_imx)
>  {
> -	u8 prescale, filt, sethold, clkhi, clklo, datavd;
> -	unsigned int clk_rate, clk_cycle;
> +	u8 prescale, filt, sethold, datavd;
> +	unsigned int clk_rate, clk_cycle, clkhi, clklo;

looks OK.

Reviewed-by: Andi Shyti <andi.shyti@kernel.org> 

there is, though, another part I would take care of, this bit:

	clklo = clk_cycle - clkhi;
	if (clklo < 64)
		break;

It might be unlikely, but if "clk_cycle > clkhi" then all the
calculation. Do you mind adding a check:

	if (unlikely(clk_cycle > clkhi))
		break;

Andi

>  	enum lpi2c_imx_pincfg pincfg;
>  	unsigned int temp;
>  
> -- 
> 2.34.1
> 

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  reply	other threads:[~2023-05-30 18:50 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-29  8:02 [PATCH] i2c: imx-lpi2c: fix type char overflow issue when calculating the clock cycle carlos.song
2023-05-29  8:02 ` carlos.song
2023-05-30 18:50 ` Andi Shyti [this message]
2023-05-30 18:50   ` Andi Shyti
2023-06-01 13:32   ` Uwe Kleine-König
2023-06-01 13:32     ` Uwe Kleine-König
2023-06-23  8:14 ` Wolfram Sang
2023-06-23  8:14   ` Wolfram Sang

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