linux-kernel - Re: [PATCH 1/2] Input: wacom_i2c - Clean up the query device fields

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Message-ID: <YWZOL2ne/DSqaJuM@google.com>
Date:   Tue, 12 Oct 2021 20:10:39 -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 1/2] Input: wacom_i2c - Clean up the query device fields

Hi Alistair,

On Sat, Oct 09, 2021 at 09:37:06PM +1000, Alistair Francis wrote:
> Improve the query device fields to be more verbose.
> 
> Signed-off-by: Alistair Francis <alistair@...stair23.me>
> ---
>  drivers/input/touchscreen/wacom_i2c.c | 49 ++++++++++++++++-----------
>  1 file changed, 30 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/wacom_i2c.c b/drivers/input/touchscreen/wacom_i2c.c
> index 22826c387da5..8d7267ccc661 100644
> --- a/drivers/input/touchscreen/wacom_i2c.c
> +++ b/drivers/input/touchscreen/wacom_i2c.c
> @@ -14,13 +14,21 @@
>  #include <linux/interrupt.h>
>  #include <asm/unaligned.h>
>  
> -#define WACOM_CMD_QUERY0	0x04
> -#define WACOM_CMD_QUERY1	0x00
> -#define WACOM_CMD_QUERY2	0x33
> -#define WACOM_CMD_QUERY3	0x02
> -#define WACOM_CMD_THROW0	0x05
> -#define WACOM_CMD_THROW1	0x00
> -#define WACOM_QUERY_SIZE	19
> +// Registers
> +#define WACOM_COMMAND_LSB   0x04
> +#define WACOM_COMMAND_MSB   0x00
> +
> +#define WACOM_DATA_LSB      0x05
> +#define WACOM_DATA_MSB      0x00
> +
> +// Report types
> +#define REPORT_FEATURE      0x30
> +
> +// Requests / operations
> +#define OPCODE_GET_REPORT   0x02
> +
> +#define WACOM_QUERY_REPORT	3
> +#define WACOM_QUERY_SIZE	22
>  
>  struct wacom_features {
>  	int x_max;
> @@ -41,27 +49,30 @@ static int wacom_query_device(struct i2c_client *client,
>  			      struct wacom_features *features)
>  {
>  	int ret;
> -	u8 cmd1[] = { WACOM_CMD_QUERY0, WACOM_CMD_QUERY1,
> -			WACOM_CMD_QUERY2, WACOM_CMD_QUERY3 };
> -	u8 cmd2[] = { WACOM_CMD_THROW0, WACOM_CMD_THROW1 };
>  	u8 data[WACOM_QUERY_SIZE];
> +
> +	u8 get_query_data_cmd[] = {
> +		WACOM_COMMAND_LSB,
> +		WACOM_COMMAND_MSB,
> +		REPORT_FEATURE | WACOM_QUERY_REPORT,
> +		OPCODE_GET_REPORT,
> +		WACOM_DATA_LSB,
> +		WACOM_DATA_MSB,
> +	};
> +
>  	struct i2c_msg msgs[] = {
> +		// Request reading of feature ReportID: 3 (Pen Query Data)
>  		{
>  			.addr = client->addr,
>  			.flags = 0,
> -			.len = sizeof(cmd1),
> -			.buf = cmd1,
> -		},
> -		{
> -			.addr = client->addr,
> -			.flags = 0,
> -			.len = sizeof(cmd2),
> -			.buf = cmd2,
> +			.len = sizeof(get_query_data_cmd),
> +			.buf = get_query_data_cmd,
>  		},
> +		// Read 21 bytes
>  		{
>  			.addr = client->addr,
>  			.flags = I2C_M_RD,
> -			.len = sizeof(data),
> +			.len = WACOM_QUERY_SIZE - 1,

Why is this change? If we are indeed supposed to read 1 byte less this
should be a separate patch.

>  			.buf = data,
>  		},
>  	};
> -- 
> 2.31.1
> 

Thanks.

-- 
Dmitry