Thank you very much for your recommendations! I had some bad experiences using a cross compiler for ARM while I tried to build a "Linux from scratch". But I will try it again and hopefully save some time ;-) Thank you, Robin 2013/6/29 Jonathan Cameron <jic23@xxxxxxxxxx>: > On 06/28/2013 10:28 AM, Robin Müller-Bady wrote: >> Hi, >> >> I'm currently writing userspace software in python and c for using >> (mainly I2C) sensors, e.g. MPL115A2 barometric pressure, on a >> raspberry pi. > Excellent! > >> I now want to port them to the IIO subsystem but I still require some help. >> * Is there any good documentation on writing those drivers ? I'm >> currently working through examples in the current git kernel version >> with assistance of the IIO Introductory slides from Maxime Ripard >> "IIO, a new kernel subsystem" but these examples are, in my opinion, >> rather difficult. > > Saddly the nature of kernel driver development is that it is hard to put > together simple examples (or perhaps I'm just no good at doing so). > I'd personally start by taking a basic driver, (perhaps accel/kxsd9) > and making sure you understand what each step is doing. > > Note this won't be a trivial exercise as you will want to drill down > through a lot of the function calls to really get the hang of it. > Another option is to first of all play with the dummy driver without the > events or buffer enabled. That is there to in a sense act as documentation > of how to do basic stuff. > >> * As raspbian (raspberry pi specific debian version) comes with a >> precompiled kernel 3.6.9, several features of IIO seem to be not yet >> included. Compiling a kernel natively on the raspi is no fun (700MHz >> ARM), so I don't want to make any mistake with the configs. > Silly question but has no one provided an appropriate cross compiler? > I certainly don't do my arm builds on an arm processor - have a nice > fast intel one for building stuff. Obviously my appologies if all you > have to hand is a raspberry pi, in which case I hope you also have a > good book to read. > > If I were you I would spend some time working out how to do a full cross compile > from scratch of a more recent kernel. I see from a quick google that > lots of people are saying 'but it is so much easier to build directly on the > pi'. All I can say is they have clearly never built anything of any size with > an frequency. Also doing kernel development on anything more than a few > months old just leads to a world of pain and makes it much harder to get > help as it's not what everyone else is working with. > >> Which >> kernel options of the current stable kernel do I require for IIO/I2C >> Sensor communication ? > Should just need relevant i2c bus support (if you can enable the actual > i2c bus driver then you'll have all the dependencies), core IIO and the > driver you want to use. Again if you enable the driver you should be fine > and it should not be available unless i2c support is present. > >> >> Thank you very much in advance! > Good luck, > > Feel free to post any questions you have about specific aspects as you > get going. >> >> Regards, >> >> Robin >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-iio" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
