linux-kernel - Re: [PATCH v3 1/2] iio: vadc: Qualcomm SPMI PMIC voltage ADC driver

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Date:	Mon, 13 Oct 2014 00:14:12 +0200
From:	Hartmut Knaack <knaack.h@....de>
To:	Stanimir Varbanov <svarbanov@...sol.com>,
	"Ivan T. Ivanov" <iivanov@...sol.com>
CC:	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Kumar Gala <galak@...eaurora.org>,
	Mark Rutland <mark.rutland@....com>,
	Grant Likely <grant.likely@...aro.org>,
	Jonathan Cameron <jic23@...nel.org>,
	Arnd Bergmann <arnd@...db.de>, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Angelo Compagnucci <angelo.compagnucci@...il.com>,
	Doug Anderson <dianders@...omium.org>,
	Fugang Duan <B38611@...escale.com>,
	Johannes Thumshirn <johannes.thumshirn@....de>,
	Jean Delvare <jdelvare@...e.de>,
	Philippe Reynes <tremyfr@...oo.fr>,
	Lee Jones <lee.jones@...aro.org>,
	Josh Cartwright <joshc@...eaurora.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	David Collins <collinsd@...eaurora.org>
Subject: Re: [PATCH v3 1/2] iio: vadc: Qualcomm SPMI PMIC voltage ADC driver

Stanimir Varbanov schrieb am 25.09.2014 17:30:
> Hi Ivan,
> 
> On 09/25/2014 03:47 PM, Ivan T. Ivanov wrote:
>>
>> Hi Stan, few comment bellow.
>>
>> On Wed, 2014-09-24 at 15:56 +0300, Stanimir Varbanov wrote:
>>> The voltage ADC is peripheral of Qualcomm SPMI PMIC chips. It has
>>> 15bits resolution and register space inside PMIC accessible across
>>> SPMI bus.
>>>
>>> The vadc driver registers itself through IIO interface.
>>>
>>> Signed-off-by: Stanimir Varbanov <svarbanov@...sol.com>
>>> Signed-off-by: Ivan T. Ivanov <iivanov@...sol.com>
>>> ---
>>>  drivers/iio/adc/Kconfig                       |   10 +
>>>  drivers/iio/adc/Makefile                      |    1 +
>>>  drivers/iio/adc/qcom-spmi-vadc.c              | 1029 +++++++++++++++++++++++++
>>>  include/dt-bindings/iio/qcom,spmi-pmic-vadc.h |  119 +++
>>>  4 files changed, 1159 insertions(+), 0 deletions(-)
>>>  create mode 100644 drivers/iio/adc/qcom-spmi-vadc.c
>>>  create mode 100644 include/dt-bindings/iio/qcom,spmi-pmic-vadc.h
>>>
>>> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
>>> index 11b048a..ec48360 100644
>>> --- a/drivers/iio/adc/Kconfig
>>> +++ b/drivers/iio/adc/Kconfig
>>> @@ -206,6 +206,16 @@ config NAU7802
>>>  	  To compile this driver as a module, choose M here: the
>>>  	  module will be called nau7802.
>>>  
>>> +config QCOM_SPMI_VADC
>>> +	tristate "Qualcomm SPMI PMIC voltage ADC"
>>> +	depends on SPMI
>>
>> + select REGMAP_SPMI
> 
> I'd suggest MFD_SPMI_PMIC symbol of the parent driver instead? The
> parent MFD PMIC driver already selects REGMAP_SPMI and depends on SPMI.
> 
>>
>> <snip>
>>
>>> +
>>> +static int vadc_read(struct vadc_priv *vadc, u16 offset, u8 *data)
>>> +{
>>> +	return regmap_bulk_read(vadc->regmap, vadc->base + offset, data, 1);
>>
>> just regmap_read() ?
> 
> No, regmap_read() expects unsigned int *val as an argument hence I will
> need temporary variable. I had a comment to rework this on the first
> version of the patchset.
> 
>>
>>> +}
>>> +
>>
>> General comment, most of the dev_dbg looks like legitimate dev_err's to me.
> 
> I've decided to not flood console with messages. If someone wants to
> debug why the driver doesn't probed he can define DEBUG.
> 
I would also say that whenever you return an error code, it would be a good idea to replace the dev_dbg with dev_err. It should just rarely occur to have such errors, and if memory consumption is no issue, then I don't see a valid reason to go the full way of recompiling, getting the new kernel(-module) on the device and maybe even reboot.
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