On Tue, 2019-09-17 at 21:47 -0300, Daniel Junho wrote: > On Tue, Sep 17, 2019 at 3:24 AM Ardelean, Alexandru > <alexandru.Ardelean@xxxxxxxxxx> wrote: > > On Mon, 2019-09-16 at 20:50 -0300, Daniel Junho wrote: > > > [External] > > > > > > Hello everybody. > > > > > > I am still learning about kernel developing. I would like to try to > > > develop a device driver for the AD7928 [1], from Analog Device. > > > > > > Can someone give some words to guide me? > > > > > > I was thinking about forking the analog kernel repo [2] but I don't > > > know to which branch should I commit to when doing a pull request. Or > > > if this is the correct way for the devices from Analog. > > > > > > > Hey, > > > > Thanks for the interest in writing the driver for this. > > > > In some cases, some new parts may have an existing driver available > > already > > that can be re-used partially or completely. > > > > You're in luck. > > There is driver seems to be partially implemented via > > drivers/iio/adc/ad7923.c > > > > I've done only a minor/quick check but the control register bits are > > compatible for the AD7928 as well. > > > > Typically, you can extend that driver and add the new parts and test > > them. > > > > So, my suggestion would be: > > 1. Get an eval-board or a AD7928 part; depending on the case we could > > help > > with this > > 2. Try to set it up with a Raspberry Pi with the eval board > > a. it looks to me that you need a 7V-9V power-supply > > b. you can hook the SPI to the test-points on the eval board > > 3. Write a basic device-tree overlay ; you can adapt something from > > other > > examples. > > Look here: > > https://github.com/analogdevicesinc/linux/blob/rpi-4.19.y/arch/arm/boot/dts/overlays/Makefile > > Usually rpi-adXXX.dts are ADI parts. > > 4. Enable the driver for the kernel. > > If using the ADI kernel, there's a guide here for RPi. > > https://wiki.analog.com/resources/tools-software/linux-build/generic/raspberrypi > > Check the branch that matches your Raspbian image (rpi-4.19.y is the > > latest) > > 5. Build the kernel > > 6. Write it to the SD-card image > > 7. Test > > 8. Modify & repeat > > > > Thanks > > Alex > > > > > [1] https://www.analog.com/en/products/ad7928.html > > > [2] https://github.com/analogdevicesinc/linux > > > > > > Daniel Junho > > Hi Alex. > > It seems that using AD7923 will be the best choice. They are very > similar. > > Thank you for your reply and suggestion. > I don't have an EVB, but at work, we have a board with the AD7928 If you have the chip already connected, then it's even better. You don't need to go through the trouble of interfacing it anymore. > using a user driver. So I will try to use it for this development, at And if you've already validated with a user-driver, it's again better, as the connections have been validated. > least for now. > > I believe that will be fun =) Should be. If this whole thing is new to you, it's always easier to start with a base/existing driver and extend than go through the process of writing it from scratch. It's mostly how I learn(ed) things: taking things apart, seeing what people have done, and then using the best ideas in my future processes. > > Daniel Junho
