HC-SRO4 ultrasonic distance driver

[greg@kroah.com (Greg KH)]

On Thu, Mar 24, 2016 at 11:38:45AM +0100, Johannes Thoma wrote:
> Hi all,
> 
> I wrote a driver for the popular HC-SRO4 ultrasonic distance sensor. It 
> is beta and has been tested
> on the Raspberry PI by me and my brother: here is the stand-alone repo:
> 
> ?https://github.com/johannesthoma/linux-hc-sro4
> 
> I would like to contribute it to the linux kernel, however I am a little 
> bit nervous reading through
> the Documentation/Submitting[Patches][Drivers] documentation (in 
> particular the How to piss off
> a kernel developer sections ;)

Don't be scared, we don't bite :)

> , so I wanted to ask if I could post the 
> patch (it will be against the
> char/mics device kernel tree at 
> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
> , I think this is the correct location) on this list first, maybe 
> someone can tell me if the formatting
> and the driver are correct..

Formatting of the code itself, or the patch?

> I also have some driver specific questions:
> 
> *) First, does it really belong to drivers/misc ? There are other 
> sensors there as well, so I suppose
> this location is right.

Probably not, if this is a sensor, it should be interacting with the IIO
layer, and not just using "random" sysfs files.

> *) As of now, I've created a new device class "distance" where the sysfs 
> control files live in (so the configuration file is
> /sys/class/distance/configure ), it works for me (tm) but I don't know
> if code that creates new device classes would be accepted. Is there
> another solution to put the control files in? Maybe under
> /sys/class/gpio?

Look into the IIO api, it should fit into there somewhere.  And if not,
that api can easily be extended to do so.

> *) I've filled out the parent device field in 
> device_create_with_groups() to NULL, I'm not sure if this
> is right.

You are correct, it isn't :)

> If I put a parent, should it be the GPIO device (the HC_SRO4 is
> attached to two GPIO pins)?

Yes, you want your device to show up properly in the device heiarachy
for all of the suspend/resume and other good things that the driver core
gives you for free.

> *) When I submit the patch, I've read that one should cc the maintainers 
> (that would be Arnd Bergmann <arnd@arndb.de> and Greg Kroah-Hartman 
> <gregkh@linuxfoundation.org>) but on what list should
> I post the patch at all? Is it lkml.org?

Use scripts/get_maintainer.pl on your patch to determine this, it
figures it out for you automagically.

> Please let me know if it ok to post the patch to this list first.

Sure, feel free to, it's always good to see code on this list :)

Hope this helps,

greg k-h