Re: Raspberry Pi I2C implementation still broken?

["William D. Jones" <thor0505%comcast.net@localhost>]

I can confirm the IOCTL is fixed, and can now successfully program I2C 
EEPROMs using NetBSD on the Pi. Since my Pi is currently a wifi-less Model 
A, I have no provisions to check out the source and try to fix the other 
issues.

On a semi-related note: I've noticed that "Getting Started with GPIO" 
documentation is limited compared to Linux. Probably a good idea would be 
for someone (probably me, when I have time) to either port some Linux helper 
libraries and/or write some documentation on how to use the I2C IOCTL.

While yes, reading the man pages and source code will get a potential hacker 
the information required to succeed*, there are some who are new to (Net)BSD 
and may just want to play around before delving into the details. It DOES 
take a bit of time to get used to where to find good sources of info 
(including the proper man page sections). Just a thought- probably would fit 
well on the wiki.

Enclosed is a link to some sample code that programs Atmel EEPROMs using the 
NetBSD IOCTL (in this case, AT24HC04B): 
https://gist.github.com/cr1901/76af0b3db9e9001a8d5b
I have verified it to work, and hopefully after this example, those who want 
to use more GPIO from the RPi can fill in the blanks. Of course, with 
minimal tweaks, this code should work on ANY platform that NetBSD supports 
that provides an I2C interface via GPIO :D.

*A FreeBSD GPIO/I2C RPi tutorial also exists, and is of course similar to 
NetBSD.


-----Original Message----- 
From: Jonathan A. Kollasch
Sent: Thursday, January 22, 2015 1:13 PM
To: William D. Jones
Cc: port-arm%NetBSD.org@localhost
Subject: Re: Raspberry Pi I2C implementation still broken?

On Mon, Jan 05, 2015 at 11:31:54AM -0500, William D. Jones wrote:
> Hello all,
>
> According to the following bug report:
> http://gnats.netbsd.org/48855,
>
> and mailing list posts:
> https://mail-index.netbsd.org/port-arm/2013/01/17/msg001714.html
> https://mail-index.netbsd.org/netbsd-bugs/2014/06/21/msg037157.html
>
> Either the IOCTL or I2C driver the Raspberry Pi I2C implementation
> is broken. I believe I may have found another bug in the
> implementation by trying to read/write an I2C EEPROM using IOCTL,
> but I'm guessing it is related to the already existing IOCTL issues
> that cause writes to always succeed. It's also possible my sample
> code is wrong :P. So, before I file a problem report: Has there been
> any progress in fixing the above I2C write errors?

There has now;
https://mail-index.netbsd.org/source-changes/2015/01/22/msg062568.html
(The ioctl was broken in certain situations.)

While port-arm/48855 and port-arm/48932 still remain, they should be easy
to fix.

Jonathan Kollasch

--
William D. Jones
Rowan University | ECE | 2012
Member IEEE
Member Tau Beta Pi
thor0505%comcast.net@localhost
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