linux-kernel - Re: Looking for good references for ARM driver development

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Date:	Wed, 19 Nov 2014 23:00:08 +0530
From:	Victor Ascroft <victorascroft@...il.com>
To:	Mason <mpeg.blue@...e.fr>
CC:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: Looking for good references for ARM driver development


On 11/19/2014 10:49 PM, Mason wrote:
> On 19/11/2014 17:57, Victor Ascroft wrote:
> 
>> This actually depends on the kernel you are using. Do you have relatively
>> new kernel or an old one? Depending on that, either you will get that
>> information in a board file or else in the device tree in arch/arm/boot/dts.
> 
> I'll reply more thoroughly later, but I wanted to address this question.
> We're targeting kernel 3.14.x

OK. Has to be a device tree then.

> 
>> This depends. If you have driver compiled in with the kernel this will happen
>> on kernel boot up. If you have the driver as a loadable module, the probe hook
>> will be called on modprobe or insmod.
> 
> Is this an answer to question 5?
> I think there is some confusion with the "probe" terminology.
> 
> I meant "probe" as in "read the current value".
> I think you mean "probe" as in "the driver probes for the device through
> the probe method."
> 
> I meant to ask how often the hwmon framework "polls" the temperature sensor.

Oh. My understanding was you meant the "probe" of the driver. The hwmon
will be exposing the functionality of reading the temperature sensor through
a sysfs interface. I am not sure as to whether a "poll" functionality is
provided by hwmon (probably not), but, when you cat or read the sysfs path 
you will have the temperature readout. The lm75.c is good place to start.

http://lxr.free-electrons.com/source/Documentation/hwmon/
http://lxr.free-electrons.com/source/Documentation/hwmon/sysfs-interface

-- Sanchayan
> 
> Regards.
> 
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