Re: [PATCH 3/3] iio: imu: Enable checking of presence of device

[Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>]

On 03/15/2014 09:04 AM, Jonathan Cameron wrote:
> On 11/03/14 21:04, Srinivas Pandruvada wrote:
> > Added logic to check presence of MPU6050 before continuing. Currently
> > only i2c writes are used in the initialzation path, which don't return
> > any error, if some i2c device responds. In this case it continues to
> > create iio devices, which don't work.
Do you think this is correct behaviour? Usually i2c devices should check 
their
identity and then only create IIO devices. Unlike PCI devices they don't 
have a common header.

Thanks,
Srinivas


> > This can be reproduced in a PC like platform, where ACPI definition
> > of this defines multiple i2c addresses.
> Yuk.
> > We need to check for an valid
> > i2c address by checking some signature before continuing.
> >
> > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
> This patch looks fine.  The test is a sensible, simple, debugging test
> even without the ACPI fun..
> > ---
> >   drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 15 ++++++++++++++-
> >   drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h  |  4 ++++
> >   2 files changed, 18 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c 
> > b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> > index 6ba565a..e062acd 100644
> > --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> > +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
> > @@ -62,6 +62,7 @@ static const struct inv_mpu6050_reg_map 
> > reg_set_6050 = {
> >       .pwr_mgmt_1             = INV_MPU6050_REG_PWR_MGMT_1,
> >       .pwr_mgmt_2             = INV_MPU6050_REG_PWR_MGMT_2,
> >       .int_pin_cfg        = INV_MPU6050_REG_INT_PIN_CFG,
> > +    .who_am_i        = INV_MPU6050_REG_WHOAMI,
> >   };
> >
> >   static const struct inv_mpu6050_chip_config chip_config_6050 = {
> > @@ -617,7 +618,7 @@ static const struct iio_info mpu_info = {
> >       .validate_trigger = inv_mpu6050_validate_trigger,
> >   };
> >
> > -int inv_set_bypass_status(struct inv_mpu6050_state *st, bool enable)
> > +static int inv_set_bypass_status(struct inv_mpu6050_state *st, bool 
> > enable)
> >   {
> >       int ret;
> >
> > @@ -650,6 +651,18 @@ static int inv_check_and_setup_chip(struct 
> > inv_mpu6050_state *st,
> >       if (result)
> >           return result;
> >       msleep(INV_MPU6050_POWER_UP_TIME);
> > +
> > +    result = i2c_smbus_read_byte_data(st->client, st->reg->who_am_i);
> > +    if (result < 0) {
> > +        dev_err(&st->client->dev, "Error reading WhoAmI\n");
> > +        return result;
> > +    }
> > +    if (result != INV_MPU6500_UNIQUE_ID) {
> > +        dev_err(&st->client->dev, "Not a valid MPU6500 device %x\n",
> > +                                result);
> > +        return -ENOSYS;
> > +    }
> > +
> >       /* toggle power state. After reset, the sleep bit could be on
> >           or off depending on the OTP settings. Toggling power would
> >           make it in a definite state as well as making the hardware
> > diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h 
> > b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
> > index de5aa22..87649bd 100644
> > --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
> > +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
> > @@ -55,6 +55,7 @@ struct inv_mpu6050_reg_map {
> >       u8 pwr_mgmt_1;
> >       u8 pwr_mgmt_2;
> >       u8 int_pin_cfg;
> > +    u8 who_am_i;
> >   };
> >
> >   /*device enum */
> > @@ -189,6 +190,9 @@ struct inv_mpu6050_state {
> >   #define INV_MPU6050_REG_INT_PIN_CFG        0x37
> >   #define INV_MPU6050_BIT_BYPASS_EN        0x2
> >
> > +#define INV_MPU6050_REG_WHOAMI            0x75
> > +#define INV_MPU6500_UNIQUE_ID            0x70
> > +
> >   /* scan element definition */
> >   enum inv_mpu6050_scan {
> >       INV_MPU6050_SCAN_ACCL_X,

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