linux-kernel - Re: [PATCH 2/8] Input: mms114 - get read of custm i2c read/write functions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 29 Jan 2018 11:01:41 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Andi Shyti <andi.shyti@...sung.com>
Cc:     Simon Shields <simon@...eageos.org>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, Andi Shyti <andi@...zian.org>
Subject: Re: [PATCH 2/8] Input: mms114 - get read of custm i2c read/write
 functions

On Mon, Jan 29, 2018 at 08:33:17PM +0900, Andi Shyti wrote:
> The 'mms114_read_reg' and 'mms114_write_reg' are used when
> reading or writing to the 'MMS114_MODE_CONTROL' register for
> updating the 'cache_mode_control' variable.
> 
> Update the 'cache_mode_control' variable in the calling
> mms114_set_active() function and get rid of all the custom i2c
> read/write functions.
> 
> With this remove also the redundant sleep of MMS114_I2C_DELAY
> (50us) between i2c operations. The waiting should to be handled
> by the i2c driver.
> 
> Signed-off-by: Andi Shyti <andi.shyti@...sung.com>
> ---
>  drivers/input/touchscreen/mms114.c | 87 +++++---------------------------------
>  1 file changed, 10 insertions(+), 77 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/mms114.c b/drivers/input/touchscreen/mms114.c
> index 0b8b1f0e8ba6..94a97049d711 100644
> --- a/drivers/input/touchscreen/mms114.c
> +++ b/drivers/input/touchscreen/mms114.c
> @@ -37,9 +37,6 @@
>  #define MMS152_FW_REV			0xE1
>  #define MMS152_COMPAT_GROUP		0xF2
>  
> -/* Minimum delay time is 50us between stop and start signal of i2c */
> -#define MMS114_I2C_DELAY		50
> -
>  /* 200ms needs after power on */
>  #define MMS114_POWERON_DELAY		200
>  
> @@ -83,76 +80,6 @@ struct mms114_touch {
>  	u8 reserved[2];
>  } __packed;
>  
> -static int __mms114_read_reg(struct mms114_data *data, unsigned int reg,
> -			     unsigned int len, u8 *val)
> -{
> -	struct i2c_client *client = data->client;
> -	struct i2c_msg xfer[2];
> -	u8 buf = reg & 0xff;
> -	int error;
> -
> -	if (reg <= MMS114_MODE_CONTROL && reg + len > MMS114_MODE_CONTROL)
> -		BUG();
> -
> -	/* Write register: use repeated start */
> -	xfer[0].addr = client->addr;
> -	xfer[0].flags = I2C_M_TEN | I2C_M_NOSTART;

So the chip does not use 10-bit addressing? What about I2C_M_NOSTART? It
is not needed also?

> -	xfer[0].len = 1;
> -	xfer[0].buf = &buf;
> -
> -	/* Read data */
> -	xfer[1].addr = client->addr;
> -	xfer[1].flags = I2C_M_RD;
> -	xfer[1].len = len;
> -	xfer[1].buf = val;
> -
> -	error = i2c_transfer(client->adapter, xfer, 2);
> -	if (error != 2) {
> -		dev_err(&client->dev,
> -			"%s: i2c transfer failed (%d)\n", __func__, error);
> -		return error < 0 ? error : -EIO;
> -	}
> -	udelay(MMS114_I2C_DELAY);
> -
> -	return 0;
> -}
> -
> -static int mms114_read_reg(struct mms114_data *data, unsigned int reg)
> -{
> -	u8 val;
> -	int error;
> -
> -	if (reg == MMS114_MODE_CONTROL)
> -		return data->cache_mode_control;
> -
> -	error = __mms114_read_reg(data, reg, 1, &val);
> -	return error < 0 ? error : val;
> -}
> -
> -static int mms114_write_reg(struct mms114_data *data, unsigned int reg,
> -			    unsigned int val)
> -{
> -	struct i2c_client *client = data->client;
> -	u8 buf[2];
> -	int error;
> -
> -	buf[0] = reg & 0xff;
> -	buf[1] = val & 0xff;
> -
> -	error = i2c_master_send(client, buf, 2);
> -	if (error != 2) {
> -		dev_err(&client->dev,
> -			"%s: i2c send failed (%d)\n", __func__, error);
> -		return error < 0 ? error : -EIO;
> -	}
> -	udelay(MMS114_I2C_DELAY);
> -
> -	if (reg == MMS114_MODE_CONTROL)
> -		data->cache_mode_control = val;
> -
> -	return 0;
> -}
> -
>  static void mms114_process_mt(struct mms114_data *data, struct mms114_touch *touch)
>  {
>  	struct i2c_client *client = data->client;
> @@ -231,19 +158,25 @@ static irqreturn_t mms114_interrupt(int irq, void *dev_id)
>  
>  static int mms114_set_active(struct mms114_data *data, bool active)
>  {
> -	int val;
> +	int val, err;
>  
> -	val = mms114_read_reg(data, MMS114_MODE_CONTROL);
> +	val = i2c_smbus_read_byte_data(data->client, MMS114_MODE_CONTROL);

If I  understand the original commit for the driver, the control
register is write only and is not to be read from, that is why we have
this cached value. With your change you read form it.

By the way, have you looked into converting it all to regmap?

>  	if (val < 0)
>  		return val;
>  
> -	val &= ~MMS114_OPERATION_MODE_MASK;
> +	val = data->cache_mode_control &= ~MMS114_OPERATION_MODE_MASK;
>  
>  	/* If active is false, sleep mode */
>  	if (active)
>  		val |= MMS114_ACTIVE;
>  
> -	return mms114_write_reg(data, MMS114_MODE_CONTROL, val);
> +	err = i2c_smbus_write_byte_data(data->client, MMS114_MODE_CONTROL, val);
> +	if (err < 0)
> +		return err;
> +
> +	data->cache_mode_control = val;
> +
> +	return 0;
>  }
>  
>  static int mms114_get_version(struct mms114_data *data)
> -- 
> 2.15.1
> 

-- 
Dmitry