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SubjectRe: [PATCH 03/16 v2] Input: atmel_mxt_ts - refactor mxt_read/write_reg to take a length
On Wed, Apr 11, 2012 at 5:05 PM, Henrik Rydberg <rydberg@bitmath.se> wrote:
>
> Hi Daniel,
>
> > The i2c bus requires 5 bytes to do a 1 byte read (1-byte i2c address + 2
> > byte offset + 1-byte i2c address + 1 byte data), or 4 bytes to do a
> > 1-byte write (1 byte i2c address + 2 byte offset + 1 byte data).
> >
> > By taking a length with reads and writes, the driver can amortize
> > transaction overhead by performing larger transactions where
> > appropriate.
> >
> > This patch just sets up the new API.  Later patches refactor
> > reads/writes
> > to take advantage of the larger transactions.
> >
> > Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
> > Reviewed-by: Joonyoung Shim <jy0922.shim@samsung.com>
> > ---
> >  drivers/input/touchscreen/atmel_mxt_ts.c |   47
> > +++++++++++++----------------
> >  1 files changed, 21 insertions(+), 26 deletions(-)
> >
> > diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c
> > b/drivers/input/touchscreen/atmel_mxt_ts.c
> > index 15ae6fd..971f9dc 100644
> > --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> > +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> > @@ -397,8 +397,7 @@ static int mxt_fw_write(struct i2c_client *client,
> >       return 0;
> >  }
> >
> > -static int __mxt_read_reg(struct i2c_client *client,
> > -                            u16 reg, u16 len, void *val)
> > +static int mxt_read_reg(struct i2c_client *client, u16 reg, u16 len,
> > void *val)
> >  {
> >       struct i2c_msg xfer[2];
> >       u8 buf[2];
> > @@ -419,28 +418,25 @@ static int __mxt_read_reg(struct i2c_client
> > *client,
> >       xfer[1].buf = val;
> >
> >       if (i2c_transfer(client->adapter, xfer, 2) != 2) {
> > -             dev_err(&client->dev, "%s: i2c transfer failed\n",
> > __func__);
> > +             dev_err(&client->dev, "%s: i2c read failed\n", __func__);
> >               return -EIO;
> >       }
> >
> >       return 0;
> >  }
> >
> > -static int mxt_read_reg(struct i2c_client *client, u16 reg, u8 *val)
> > +static int mxt_write_reg(struct i2c_client *client, u16 reg, u16 len,
> > +                      const void *val)
> >  {
> > -     return __mxt_read_reg(client, reg, 1, val);
> > -}
> > -
> > -static int mxt_write_reg(struct i2c_client *client, u16 reg, u8 val)
> > -{
> > -     u8 buf[3];
> > +     size_t count = 2 + len;         /* + 2-byte offset */
> > +     u8 buf[count];
>
> How much stack space are you planning to use here?

I missed this one when removing the other stack allocated array since
they are (rightly) frowned upon in the kernel. I will replace with a
malloc, unless you have a better suggestion?

>
> >
> >       buf[0] = reg & 0xff;
> >       buf[1] = (reg >> 8) & 0xff;
> > -     buf[2] = val;
> > +     memcpy(&buf[2], val, len);
> >
> > -     if (i2c_master_send(client, buf, 3) != 3) {
> > -             dev_err(&client->dev, "%s: i2c send failed\n", __func__);
> > +     if (i2c_master_send(client, buf, count) != count) {
> > +             dev_err(&client->dev, "%s: i2c write failed\n", __func__);
> >               return -EIO;
> >       }
> >
> > @@ -450,8 +446,7 @@ static int mxt_write_reg(struct i2c_client *client,
> > u16 reg, u8 val)
> >  static int mxt_read_object_table(struct i2c_client *client,
> >                                     u16 reg, u8 *object_buf)
> >  {
> > -     return __mxt_read_reg(client, reg, MXT_OBJECT_SIZE,
> > -                                object_buf);
> > +     return mxt_read_reg(client, reg, MXT_OBJECT_SIZE, object_buf);
> >  }
> >
> >  static struct mxt_object *
> > @@ -481,8 +476,8 @@ static int mxt_read_message(struct mxt_data *data,
> >               return -EINVAL;
> >
> >       reg = object->start_address;
> > -     return __mxt_read_reg(data->client, reg,
> > -                     sizeof(struct mxt_message), message);
> > +     return mxt_read_reg(data->client, reg, sizeof(struct mxt_message),
> > +                         message);
> >  }
> >
> >  static int mxt_read_object(struct mxt_data *data,
> > @@ -496,7 +491,7 @@ static int mxt_read_object(struct mxt_data *data,
> >               return -EINVAL;
> >
> >       reg = object->start_address;
> > -     return __mxt_read_reg(data->client, reg + offset, 1, val);
> > +     return mxt_read_reg(data->client, reg + offset, 1, val);
> >  }
> >
> >  static int mxt_write_object(struct mxt_data *data,
> > @@ -510,7 +505,7 @@ static int mxt_write_object(struct mxt_data *data,
> >               return -EINVAL;
> >
> >       reg = object->start_address;
> > -     return mxt_write_reg(data->client, reg + offset, val);
> > +     return mxt_write_reg(data->client, reg + offset, 1, &val);
> >  }
> >
> >  static void mxt_input_report(struct mxt_data *data, int single_id)
> > @@ -757,27 +752,27 @@ static int mxt_get_info(struct mxt_data *data)
> >       int error;
> >       u8 val;
> >
> > -     error = mxt_read_reg(client, MXT_FAMILY_ID, &val);
> > +     error = mxt_read_reg(client, MXT_FAMILY_ID, 1, &val);
> >       if (error)
> >               return error;
> >       info->family_id = val;
> >
> > -     error = mxt_read_reg(client, MXT_VARIANT_ID, &val);
> > +     error = mxt_read_reg(client, MXT_VARIANT_ID, 1, &val);
> >       if (error)
> >               return error;
> >       info->variant_id = val;
> >
> > -     error = mxt_read_reg(client, MXT_VERSION, &val);
> > +     error = mxt_read_reg(client, MXT_VERSION, 1, &val);
> >       if (error)
> >               return error;
> >       info->version = val;
> >
> > -     error = mxt_read_reg(client, MXT_BUILD, &val);
> > +     error = mxt_read_reg(client, MXT_BUILD, 1, &val);
> >       if (error)
> >               return error;
> >       info->build = val;
> >
> > -     error = mxt_read_reg(client, MXT_OBJECT_NUM, &val);
> > +     error = mxt_read_reg(client, MXT_OBJECT_NUM, 1, &val);
> >       if (error)
> >               return error;
> >       info->object_num = val;
> > @@ -860,12 +855,12 @@ static int mxt_initialize(struct mxt_data *data)
> >       msleep(MXT_RESET_TIME);
> >
> >       /* Update matrix size at info struct */
> > -     error = mxt_read_reg(client, MXT_MATRIX_X_SIZE, &val);
> > +     error = mxt_read_reg(client, MXT_MATRIX_X_SIZE, 1, &val);
> >       if (error)
> >               return error;
> >       info->matrix_xsize = val;
> >
> > -     error = mxt_read_reg(client, MXT_MATRIX_Y_SIZE, &val);
> > +     error = mxt_read_reg(client, MXT_MATRIX_Y_SIZE, 1, &val);
> >       if (error)
> >               return error;
> >       info->matrix_ysize = val;
> > --
> > 1.7.7.3
> >
>
> Thanks,
> Henrik
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