linux-kernel - Re: [PATCH 1/2] ti-adc081c: Add support for adc101c* and adc121c*

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Message-ID: <5700DF74.4030709@kernel.org>
Date:	Sun, 3 Apr 2016 10:16:36 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	Crestez Dan Leonard <leonard.crestez@...el.com>,
	linux-iio@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald-Stadler <pmeerw@...erw.net>,
	Daniel Baluta <daniel.baluta@...el.com>,
	Thierry Reding <thierry.reding@...onic-design.de>
Subject: Re: [PATCH 1/2] ti-adc081c: Add support for adc101c* and adc121c*

On 31/03/16 18:20, Crestez Dan Leonard wrote:
> These chips has an almost identical interface but a deal with a
> different number of value bits. Datasheet links for comparison:
> 
>  * http://www.ti.com/lit/ds/symlink/adc081c021.pdf
>  * http://www.ti.com/lit/ds/symlink/adc101c021.pdf
>  * http://www.ti.com/lit/ds/symlink/adc121c021.pdf
> 
> Signed-off-by: Crestez Dan Leonard <leonard.crestez@...el.com>
Just one query inline.

J
> ---
>  drivers/iio/adc/Kconfig      |  6 +++---
>  drivers/iio/adc/ti-adc081c.c | 31 +++++++++++++++++++++++++++----
>  2 files changed, 30 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 9ddcd5d..a2d0db5 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -378,11 +378,11 @@ config ROCKCHIP_SARADC
>  	  module will be called rockchip_saradc.
>  
>  config TI_ADC081C
> -	tristate "Texas Instruments ADC081C021/027"
> +	tristate "Texas Instruments ADC081C/ADC101C/ADC121C family"
>  	depends on I2C
>  	help
> -	  If you say yes here you get support for Texas Instruments ADC081C021
> -	  and ADC081C027 ADC chips.
> +	  If you say yes here you get support for Texas Instruments ADC081C,
> +	  ADC101C and ADC121C ADC chips.
>  
>  	  This driver can also be built as a module. If so, the module will be
>  	  called ti-adc081c.
> diff --git a/drivers/iio/adc/ti-adc081c.c b/drivers/iio/adc/ti-adc081c.c
> index ecbc121..9b2f26f 100644
> --- a/drivers/iio/adc/ti-adc081c.c
> +++ b/drivers/iio/adc/ti-adc081c.c
> @@ -1,9 +1,21 @@
>  /*
> + * TI ADC081C/ADC101C/ADC121C 8/10/12-bit ADC driver
> + *
>   * Copyright (C) 2012 Avionic Design GmbH
> + * Copyright (C) 2016 Intel
>   *
>   * This program is free software; you can redistribute it and/or modify
>   * it under the terms of the GNU General Public License version 2 as
>   * published by the Free Software Foundation.
> + *
> + * Datasheets:
> + * 	http://www.ti.com/lit/ds/symlink/adc081c021.pdf
> + * 	http://www.ti.com/lit/ds/symlink/adc101c021.pdf
> + *	http://www.ti.com/lit/ds/symlink/adc121c021.pdf
> + *
> + * The devices have a very similar interface and differ mostly in the number of
> + * bits handled. For the 8-bit and 10-bit models the least-significant 4 or 2
> + * bits of value registers are reserved.
>   */
>  
>  #include <linux/err.h>
> @@ -17,6 +29,9 @@
>  struct adc081c {
>  	struct i2c_client *i2c;
>  	struct regulator *ref;
> +
> +	/* 8, 10 or 12 */
> +	int bits;
>  };
>  
>  #define REG_CONV_RES 0x00
> @@ -34,7 +49,7 @@ static int adc081c_read_raw(struct iio_dev *iio,
>  		if (err < 0)
>  			return err;
>  
> -		*value = (err >> 4) & 0xff;
> +		*value = (err & 0xFFF) >> (12 - adc->bits);
>  		return IIO_VAL_INT;
>  
>  	case IIO_CHAN_INFO_SCALE:
> @@ -43,7 +58,7 @@ static int adc081c_read_raw(struct iio_dev *iio,
>  			return err;
>  
>  		*value = err / 1000;
> -		*shift = 8;
> +		*shift = adc->bits;
>  
>  		return IIO_VAL_FRACTIONAL_LOG2;
>  
> @@ -72,6 +87,9 @@ static int adc081c_probe(struct i2c_client *client,
>  	struct adc081c *adc;
>  	int err;
>  
> +	if (id->driver_data != 8 && id->driver_data != 10 && id->driver_data != 12)
> +		return -EINVAL;
How could this condition occur?  The driver won't be probed if we don't have
a match on one of the items in the id table and they all obey this rull?

On Peter's comment, it would be future proofing to use an index into a
information structure array, but I'd prefer that to be added when needed and
am reasonably happy with how you have it here.
> +
>  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
>  		return -EOPNOTSUPP;
>  
> @@ -81,6 +99,7 @@ static int adc081c_probe(struct i2c_client *client,
>  
>  	adc = iio_priv(iio);
>  	adc->i2c = client;
> +	adc->bits = id->driver_data;
>  
>  	adc->ref = devm_regulator_get(&client->dev, "vref");
>  	if (IS_ERR(adc->ref))
> @@ -124,7 +143,9 @@ static int adc081c_remove(struct i2c_client *client)
>  }
>  
>  static const struct i2c_device_id adc081c_id[] = {
> -	{ "adc081c", 0 },
> +	{ "adc081c",  8 },
> +	{ "adc101c", 10 },
> +	{ "adc121c", 12 },
>  	{ }
>  };
>  MODULE_DEVICE_TABLE(i2c, adc081c_id);
> @@ -132,6 +153,8 @@ MODULE_DEVICE_TABLE(i2c, adc081c_id);
>  #ifdef CONFIG_OF
>  static const struct of_device_id adc081c_of_match[] = {
>  	{ .compatible = "ti,adc081c" },
> +	{ .compatible = "ti,adc101c" },
> +	{ .compatible = "ti,adc121c" },
>  	{ }
>  };
>  MODULE_DEVICE_TABLE(of, adc081c_of_match);
> @@ -149,5 +172,5 @@ static struct i2c_driver adc081c_driver = {
>  module_i2c_driver(adc081c_driver);
>  
>  MODULE_AUTHOR("Thierry Reding <thierry.reding@...onic-design.de>");
> -MODULE_DESCRIPTION("Texas Instruments ADC081C021/027 driver");
> +MODULE_DESCRIPTION("Texas Instruments ADC081C/ADC101C/ADC121C driver");
>  MODULE_LICENSE("GPL v2");
>