Re: [lm-sensors] [PATCH v2] hwmon (ds1621): Remove detection function

[Robert Coulson <rob.coulson@gmail.com>]

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On Mon, May 20, 2013 at 11:26 PM, Jean Delvare <khali@linux-fr.org> wrote:

> Hi Robert,
>

Good morning Jean,


>
> On Mon, 20 May 2013 17:29:29 -0700, Robert Coulson wrote:
> > v2:
> > - removed detect function references in ds1621 documentation
> > - replaced deprecated with removed and fixed a spelling error
>
> Note: the patch changes history should go below, between the "---" and
> the diffstat, so that it doesn't make it to git.


Thank you for the info, I appreciate it and will do so in the future.


>


> Almost there, see my comments inline.
>
> >
> > Due to a lack of device and vendor identification registers, the
> > Dallas/Maxim DS16xx devices cannot be uniquely detected, sometimes
> > resulting in false positives. Therefore, the detection function is
> > being removed in favor of explicit device instantiation.
> >
> > These changes are based on the 3.9 source base and intended for
> > hwmon-next.
> >
> > Signed-off-by: Robert Coulson <rob.coulson@gmail.com>
> > ---
> >  Documentation/hwmon/ds1621 |   13 ++++---------
> >  drivers/hwmon/ds1621.c     |   43
> -------------------------------------------
> >  2 files changed, 4 insertions(+), 52 deletions(-)
> >
> > diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621
> > index 140eab5..009aabb 100644
> > --- a/Documentation/hwmon/ds1621
> > +++ b/Documentation/hwmon/ds1621
> > @@ -8,9 +8,7 @@ Supported chips:
> >      Datasheet: Publicly available from www.maximintegrated.com
> >
> >    * Dallas Semiconductor DS1625
> > -    Prefix:
> > -     'ds1621' - if binding via _detect function
> > -     'ds1625' - explicit instantiation
> > +    Prefix: 'ds1625'
> >      Addresses scanned: I2C 0x48 - 0x4f
>
> You much change these lists to "none", as the driver will no longer
> scan any address.
>

agreed.


>
> >      Datasheet: Publicly available from www.datasheetarchive.com
> >
> > @@ -77,12 +75,9 @@ The DS1625 is pin compatible and functionally
> equivalent with the DS1621,
> >  but the DS1621 is meant to replace it. The DS1631 and DS1721 are also
> >  pin compatible with the DS1621, but provide multi-resolution support.
> >
> > -Since there is no version register, there is no unique identification
> > -for these devices. In addition, the DS1631 and DS1721 will emulate a
> > -DS1621 device, if not explicitly instantiated (why? because the detect
> > -function compares the temperature register values bits and checks for a
> > -9-bit resolution). Therefore, for correct device identification and
> > -functionality, explicit device instantiation is required.
> > +Since there is no version or vendor identification register, there is
> > +no unique identification for these devices. Therefore, explicit device
> > +instantiation is required for correct device identification and
> functionality.
> >
> >  The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0
> >  degree Celius over a -10 to +85 degree range, a minimum/maximum alarm
> > diff --git a/drivers/hwmon/ds1621.c b/drivers/hwmon/ds1621.c
> > index d4f02a8..124fc83 100644
> > --- a/drivers/hwmon/ds1621.c
> > +++ b/drivers/hwmon/ds1621.c
> > @@ -360,48 +360,6 @@ static const struct attribute_group ds1621_group = {
> >       .is_visible = ds1621_attribute_visible
> >  };
> >
> > -
> > -/* Return 0 if detection is successful, -ENODEV otherwise */
> > -static int ds1621_detect(struct i2c_client *client,
> > -                      struct i2c_board_info *info)
> > -{
> > -     struct i2c_adapter *adapter = client->adapter;
> > -     int conf, temp;
> > -     int i;
> > -
> > -     if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA
> > -                                  | I2C_FUNC_SMBUS_WORD_DATA
> > -                                  | I2C_FUNC_SMBUS_WRITE_BYTE))
> > -             return -ENODEV;
> > -
> > -     /*
> > -      * Now, we do the remaining detection. It is lousy.
> > -      *
> > -      * The NVB bit should be low if no EEPROM write has been requested
> > -      * during the latest 10ms, which is highly improbable in our case.
> > -      */
> > -     conf = i2c_smbus_read_byte_data(client, DS1621_REG_CONF);
> > -     if (conf < 0 || conf & DS1621_REG_CONFIG_NVB)
> > -             return -ENODEV;
> > -     /*
> > -      * The ds1621 & ds1625 use 9-bit resolution, so the 7 lowest bits
> > -      * of the temperature should always be 0 (NOTE: The other chips
> > -      * have multi-resolution support, so if they have 9-bit resolution
> > -      * configured and the min/max temperature values set accordingly,
> > -      * then if not explicitly instantiated, they *will* appear as and
> > -      * emulate a ds1621 device).
> > -      */
> > -     for (i = 0; i < ARRAY_SIZE(DS1621_REG_TEMP); i++) {
> > -             temp = i2c_smbus_read_word_data(client,
> DS1621_REG_TEMP[i]);
> > -             if (temp < 0 || (temp & 0x7f00))
> > -                     return -ENODEV;
> > -     }
> > -
> > -     strlcpy(info->type, "ds1621", I2C_NAME_SIZE);
> > -
> > -     return 0;
> > -}
> > -
> >  static int ds1621_probe(struct i2c_client *client,
> >                       const struct i2c_device_id *id)
> >  {
> > @@ -467,7 +425,6 @@ static struct i2c_driver ds1621_driver = {
> >       .probe          = ds1621_probe,
> >       .remove         = ds1621_remove,
> >       .id_table       = ds1621_id,
> > -     .detect         = ds1621_detect,
> >       .address_list   = normal_i2c,
>
> This address list can be removed as well, as it is only used to
> determine when the detect callback should be called.
>

agreed and nice catch.


>
> >  };
> >
>
> Thanks,
> --
> Jean Delvare
>

Your welcome.

I'll send an updated patch set shortly.

Rob

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