Matthijs, Where would be a good start to read up on uio ? I've been reading around, but have not found anything of much use yet. Also, that pastebin you gave, this is *everything* needed to use an uio adc ?
But for instance, assuming the pastebin you gave is everything needed( which would be awesome ), how do I know how this adc uio "object" is set up ? e.g. how would i write a userspace driver for it ? I have so many questions, but no idea where to start looking for answers . . . On Tue, Nov 3, 2015 at 8:49 PM, Matthijs van Duin <[email protected] > wrote: > On 4 November 2015 at 03:40, Pierre-Louis Constant <[email protected]> > wrote: > >> you guys provided me enough info leads for a whole year of insomnia. >> > > haha, sorry :-) > > >> Correct, pretty much anything can be used from userspace like that, >>> although some people will frown at you for bypassing the kernel if you do. >> >> >> Righteo, so far I was using the somewhat slow (but easy) way thyrough FS, >> however I am stuck with running my program as root, as I can't access the >> PWM (or hardware) as normal user. Using the mmap() method would be >> permission free, would it ? >> > > other way around: you can simply change owner/group/permissions in sysfs > if you want to (although obviously it won't persist across reboots, hence > would need to be done e.g. in an udev rule). > > /dev/mem however always requires root permissions to open. You can of > course open it and then drop permissions (and close the descriptor after > mmapping the regions you need). The same is true for other files and > devices of course, including sysfs files. > > uio is the cleanest here: the pastebin I linked to actually included an > example udev rule for setting group and permissions. > > sysfs files aren't devices hence you can't set their permissions in the > same way but need to do something ugly like RUN="/bin/chmod ...". It's > still wise to do it in an udev rule rather than a fixed startup script > since it may run too early and the files may not exist yet. > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
