linux-kernel - Re: [PATCH 2/2] Input: wacom_i2c

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Date:   Tue, 12 Oct 2021 20:55:55 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Alistair Francis <alistair@...stair23.me>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        alistair23@...il.com
Subject: Re: [PATCH 2/2] Input: wacom_i2c - Use macros for the bit masks

Hi Alistair,

On Sat, Oct 09, 2021 at 09:37:07PM +1000, Alistair Francis wrote:
> To make the code easier to read use macros for the bit masks.
> 
> Signed-off-by: Alistair Francis <alistair@...stair23.me>
> ---
>  drivers/input/touchscreen/wacom_i2c.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/wacom_i2c.c b/drivers/input/touchscreen/wacom_i2c.c
> index 8d7267ccc661..6865342db659 100644
> --- a/drivers/input/touchscreen/wacom_i2c.c
> +++ b/drivers/input/touchscreen/wacom_i2c.c
> @@ -14,6 +14,12 @@
>  #include <linux/interrupt.h>
>  #include <asm/unaligned.h>
>  
> +// Bitmasks (for data[3])
> +#define WACOM_TIP_SWITCH_bm         (1 << 0)
> +#define WACOM_BARREL_SWITCH_bm      (1 << 1)
> +#define WACOM_ERASER_bm             (1 << 2)
> +#define WACOM_BARREL_SWITCH_2_bm    (1 << 4)

We have BIT() for that.

By the way, do you know what is the good name for bit 3? I see it is
being used in:

        if (!wac_i2c->prox)
                wac_i2c->tool = (data[3] & 0x0c) ?
                        BTN_TOOL_RUBBER : BTN_TOOL_PEN;

        wac_i2c->prox = data[3] & WACOM_IN_PROXIMITY;

0x0c is (WACOM_ERASER | <something else>).

Also, I am a bit confused by this code, now that I look at it closer.
Are we saying that the tool type (eraser or something else) is set only
in first packet for contact/touch?

> +
>  // Registers
>  #define WACOM_COMMAND_LSB   0x04
>  #define WACOM_COMMAND_MSB   0x00
> @@ -110,10 +116,10 @@ static irqreturn_t wacom_i2c_irq(int irq, void *dev_id)
>  	if (error < 0)
>  		goto out;
>  
> -	tsw = data[3] & 0x01;
> -	ers = data[3] & 0x04;
> -	f1 = data[3] & 0x02;
> -	f2 = data[3] & 0x10;
> +	tsw = data[3] & WACOM_TIP_SWITCH_bm;
> +	ers = data[3] & WACOM_ERASER_bm;
> +	f1 = data[3] & WACOM_BARREL_SWITCH_bm;
> +	f2 = data[3] & WACOM_BARREL_SWITCH_2_bm;
>  	x = le16_to_cpup((__le16 *)&data[4]);
>  	y = le16_to_cpup((__le16 *)&data[6]);
>  	pressure = le16_to_cpup((__le16 *)&data[8]);
> -- 
> 2.31.1
> 

How about the version of the patch below?

-- 
Dmitry

Input: wacom_i2c - use macros for the bit masks

From: Alistair Francis <alistair@...stair23.me>

To make the code easier to read use macros for the bit masks.

Signed-off-by: Alistair Francis <alistair@...stair23.me>
Link: https://lore.kernel.org/r/20211009113707.17568-2-alistair@alistair23.me
Patchwork-Id: 12547519
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---
 drivers/input/touchscreen/wacom_i2c.c |   19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/input/touchscreen/wacom_i2c.c b/drivers/input/touchscreen/wacom_i2c.c
index 22826c387da5..d3ea9aa8a98c 100644
--- a/drivers/input/touchscreen/wacom_i2c.c
+++ b/drivers/input/touchscreen/wacom_i2c.c
@@ -6,6 +6,7 @@
  * <tobita.tatsunosuke@...om.co.jp>
  */
 
+#include <linux/bits.h>
 #include <linux/module.h>
 #include <linux/input.h>
 #include <linux/i2c.h>
@@ -14,6 +15,14 @@
 #include <linux/interrupt.h>
 #include <asm/unaligned.h>
 
+// Bitmasks (for data[3])
+#define WACOM_TIP_SWITCH	BIT(0)
+#define WACOM_BARREL_SWITCH	BIT(1)
+#define WACOM_ERASER		BIT(2)
+#define WACOM_BARREL_SWITCH_2	BIT(4)
+#define WACOM_IN_PROXIMITY	BIT(5)
+
+// Registers
 #define WACOM_CMD_QUERY0	0x04
 #define WACOM_CMD_QUERY1	0x00
 #define WACOM_CMD_QUERY2	0x33
@@ -99,10 +108,10 @@ static irqreturn_t wacom_i2c_irq(int irq, void *dev_id)
 	if (error < 0)
 		goto out;
 
-	tsw = data[3] & 0x01;
-	ers = data[3] & 0x04;
-	f1 = data[3] & 0x02;
-	f2 = data[3] & 0x10;
+	tsw = data[3] & WACOM_TIP_SWITCH;
+	ers = data[3] & WACOM_ERASER;
+	f1 = data[3] & WACOM_BARREL_SWITCH;
+	f2 = data[3] & WACOM_BARREL_SWITCH_2;
 	x = le16_to_cpup((__le16 *)&data[4]);
 	y = le16_to_cpup((__le16 *)&data[6]);
 	pressure = le16_to_cpup((__le16 *)&data[8]);
@@ -111,7 +120,7 @@ static irqreturn_t wacom_i2c_irq(int irq, void *dev_id)
 		wac_i2c->tool = (data[3] & 0x0c) ?
 			BTN_TOOL_RUBBER : BTN_TOOL_PEN;
 
-	wac_i2c->prox = data[3] & 0x20;
+	wac_i2c->prox = data[3] & WACOM_IN_PROXIMITY;
 
 	input_report_key(input, BTN_TOUCH, tsw || ers);
 	input_report_key(input, wac_i2c->tool, wac_i2c->prox);