linux-kernel - Re: [PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

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Date:	Wed, 16 Mar 2016 21:02:51 +0100
From:	Slawomir Stepien <sst@...zta.fm>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Peter Meerwald-Stadler <pmeerw@...erw.net>, jic23@...nel.org,
	knaack.h@....de, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: add driver for Microchip MCP414X/416X/424X/426X

On Mar 16, 2016 19:24, Lars-Peter Clausen wrote:
> On 03/16/2016 05:25 PM, Slawomir Stepien wrote:
> > On Mar 16, 2016 13:30, Peter Meerwald-Stadler wrote:
> [...]
> >> plenty of the private API, some of which seems to be debug only?
> >> what is really needed to interact with a poti?
> > 
> > I wanted to export both the non volatile and volatile memory addresses for wiper
> > position access. That is bare minimum for the poti to operate.
> > 
> > But I also wanted to export additional features of this chip. That is way there
> > is increase and decrease API, and STATUS and TCON register access.
> > 
> 
> The important part about a framework and the associated device drivers
> is to expose the features of a device using a standardized interface so
> you can write generic applications/libraries and share infrastructure.
> If an application requires device specific knowledge to access the
> features of a device you may as well write a userspace driver using i2cdev.
> 
> So when you are introducing new ABI it should at least follow the
> standard naming scheme. And also try to think whether this is a feature
> that is present in other similar devices and come up with a device
> independent way to expose this functionality.
> 
> Let's start with the simple stuff, I don't really see the advantage of
> having separate inc/dec controls. This can be handled through the
> standard raw attribute. If the newly written value is one off from the
> previous one use inc/dec otherwise write it directly. And even then it
> might make sense to just ignore that and always write the raw value.

I've got your point. The version 2 will use only the IIO facilities. Then I will
try to build more based on that.

> > The memory_map API is a way to access all the not used by chip memory addresses.
> > This API I think could be deleted. But I still think that some people might find
> > it useful.
> 
> This sounds more like it should maybe be exposed as a standard EEPROM
> device.

Not quite familiar with this, but will look into that.

Once more thank you for comments.

-- 
Slawomir Stepien