has anyone got a linux kernel driver for mcp79410 rtc  -solved

Hi Tim!

You want the ds1307 driver, however it sort of depends which kernel you're running, the patch to add the mcp7941x series isn't in the 3.1.9+ kernel that's default in most of the current distros.  If you're ok with patching your kernel and re-compling it then you can find the patch here: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=43fcb81550f7a16be192b19c77a379c9b27b1585 but be aware that it may not apply cleanly to the older kernel depending on what other changes there were.

However the patch did make it into 3.2, so if you don't want to mess with kernel compiling then have a look at Chris Boots kernel http://www.bootc.net/projects/raspberry-pi-kernel/

I'd also suggest asking Raspberry Pi questions over in the Raspberry Pi section http://www.element14.com/community/groups/raspberry-pi?ICID=technologies_rpi_menubar. There's a fair number of us over there willing to help, but we're not necessarily going to see stuff here in the Experts section.

thanks very much selsinork.

My next challenge will be to get the 3.1.9 kernel source for my current armedslack install on my raspberrypi, as the source is not at kernel.org anymore;

or, find out the config with special raspberrypi blobs and patches and see if I can get the 3.6rc1 kernel built instead. I'll post in the raspberry pi section in future, but there still seams to be a problem with posts dissapearing entirely on all the forums here at element14/farnell

http://www.kernel.org/pub/linux/kernel/v3.x/linux-3.1.9.tar.gz still seems to be there..

'official' 3.1.9 kernel source for the Pi is available here https://github.com/raspberrypi/linux and this will include all the necessary drivers.

You're unlikely to get 3.6rc1 working, there are too many missing pieces and there's a lot of changes to arm code between 3.1.9 and 3.6 making forward porting it far from simple..

That said, if you're a wizard kernel developer then you should go look at  https://github.com/lp0/linux Simon Arlott and Chris Boot have done a bunch of work in this direction. You'll need this too https://github.com/raspberrypi/linux/wiki/Device-Tree-port and you probably want to sign up to the mailing list http://lists.infradead.org/mailman/listinfo/linux-rpi-kernel

It appears that either an admin moved the thread into the Raspberry Pi area, or it magically disappeared only to turn up in the right place on it's own

well I'm not a wizard kernel developer, I've compiled a few custom kernels for pc's but that's about it. Thanks for the pointer to the 3.1.9 kernel source. I should have hunted further on the site. I'l get that downloaded and see I can get the rtc module happy.

just an update. I tried the patch on the kernel and it didn't like it, so I manually put in the changes roughly comparing them with the 3.6rc1. with modifying the include/linux/vermagic.h I can get the module to compile, but when I try insmod rtc-ds1307.ko it complains of an "-1 unknown symbol in module". the joys :-(

What version of the kernel were you modifying for those changes in 3.6rc1?  The Foundation's 3.1.9+?

(btw, in case it's any help, I wrote this document awhile back http://www.element14.com/community/docs/DOC-44948/l/compiling-linux-kernel-staging-driver-modules)

yes, the 3.1.9+ one from github/raspberrypi/linux, although it looks like it may now have moved up a subversion - see https://github.com/raspberrypi/linux/blob/rpi-3.2.27/Makefile

I'll have a look at your kernel (cross) compiling guide drew, and try that. I think part of the problem is that my slackware distribution was using the 3.1.9 kernel, but still had 2.6.38.4 source present as well. (in /usr/src). I used david (spencer's) kernel+installer from http://www.daves-collective.co.uk/raspi/images/raspi-slack-installer_01Aug12.img.xz

since this post slackware 14.0 (and armedslack 14.0 ) has come out. this updates the source framework to 3.4.11

hopefully dave will update his kernel installer/package for slackware from the 3.1.9 version to a 3.2.x or higher, as I belive that is required to add the rtc device to the kernel using the method posted http://www.element14.com/community/groups/raspberry-pi/blog/2012/07/19/what-time-is-it-adding-a-rtc-to-the-raspberry-pi-via-i2c 

I am looking forward to testing the little module I made to see if it works!

I've just updated to the 3.6.1 kernel,(with slackware 14.0) and have been able to compile the rtc-ds1703 kernel module.

I can install it with modprobe, but don't know how to tell the module that the device is at 0x6f on the i2c-0 port (ie. mcp79410) instead of 0x68 (ds1307) .

i have /dev/i2c-0 and /dev/i2c-1 and if i do a i2cdetect 0 -y it shows the device at 0x6f

i have tried

echo mcp7941x 0x6f > /sys/class/i2c-adapter/i2c-0/new_device

but I just get "no such file or directory" which is not a suprise as /sys/class/i2c-adapter does not exist. /sys/class/i2c-dev does, but substituting (ie using echo mcp7941x 0x6f > /sys/class/i2c-dev/i2c-0/new_device  ) still complains with error

-bash /sys/class/i2c-dev/i2c-0/new_device: No such file or directory

modprobe rtc-ds1307

echo mcp7941x 0x6f > /sys/bus/i2c/devices/i2c-0/new_device

works for me on a slightly older kernel.. I've not checked 3.6.1 (why can't they stick to mainline ?) but if /sys/class/i2c-adapter doesn't exist, it's possible you're missing some other stuff. Do you have i2c-dev compiled in or loaded as a module ?

Based on my older kernel it appears you'd want to use /sys/class/i2c-dev/i2c-0/device/new_device if you use that path.

Have you read Documentation/i2c/instantiating-devices in the kernel tree ?   There's a couple of ways in there to get the device configured, my personal choice is to use platform data (i.e. method 1) which also lets you configure the kernel to automatically set the clock on boot.

you hit the nail on the head, thanks. I just had a thought last night to look for "new_device" anywhere in the /sys/class/i2c-dev path and came up with the same location.

so, once the rtc module is loaded with modprobe i2c:mcp7941x  (or insmod rtc_ds1307   )

echo mcp7941x 0x6f > /sys/class/i2c-dev/i2c-0/device/new_device

creates the /dev/rtc0 device, and after a bit of prodding*, hwclock -w set the time on the rtc, and hwclock -s can now be used in /etc/rc.d/rc.local to set the system time from the rtc (and hwclock -r shows the rtc time and date)

*(to explain the prodding. initially after running above, I got ioctl errors when running hwclock. I then did

cat /dev/rtc0

  (and ctl-c ), and that seemed to fix the problem. I could then set the rtc with hwclock -w   .the proper behaviour was preserved after a cold restart of the raspberrypi  )

Info for other armedslack raspberrypi users

you need to recompile the kernel and add rtc support. specifically

CONFIG_RTC_LIB=y

CONFIG_RTC_CLASS=y

CONFIG_RTC_HCTOSYS=y

CONFIG_RTC_HCTOSYS_DEVICE="rtc0"

CONFIG_RTC_INTF_SYSFS=y

CONFIG_RTC_INTF_PROC=y

CONFIG_RTC_INTF_DEV=y

 

CONFIG_RTC_DRV_DS1307=m

I used the the kernel, modules and kernel source from http://ponce.cc/slackware/slackwarearm-14.0/raspi-slackbuild-3.6.y/  (thanks to ponce) as a starting point.

then compile and install i2c-tools from slackbuilds.org (sbopkg). this gives the i2c-dev module, so you can "talk" to i2c bus and provides the i2cdetect and i2cdump and similar tools for

probing the i2c busses.

my /etc/rc.d/rc.local includes the following lines at the bottom

modprobe i2c-dev

modprobe i2c:mcp7941x

echo mcp7941x 0x6f > /sys/class/i2c-dev/i2c-0/device/new_device

hwclock -s

Now I know my rtc gadget works, I'll have to find somewhere to post the circuit layouts for folks so they can make their own. The mcp79410 is quite a bit cheaper than the ds1307 and happens to run at 3.3v so you don't need any 5v-3.3v 2way buffering on the i2c bus. It also has battery backup function.

thanks again for your assistance selsinork et-al