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

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Date:   Wed, 13 Oct 2021 23:05:58 +1000
From:   Alistair Francis <alistair23@...il.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Alistair Francis <alistair@...stair23.me>,
        linux-input <linux-input@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] Input: wacom_i2c - Clean up the query device fields

On Wed, Oct 13, 2021 at 1:10 PM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
>
> 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.

It shouldn't be a change, we are still reading 21 bytes of data. We
are just using a macro instead of sizeof().

Alistair