In all honesty, there really should be no hotplug anyhow. At not for this sort of thing. The device should be powered down when wiring new circuitry to it anyhow right ?
On Mon, Dec 2, 2013 at 5:15 PM, Charles Steinkuehler < char...@steinkuehler.net> wrote: > On 12/2/2013 5:48 PM, William Hermans wrote: > > Charles, where do you get your information from ? Not trying to be rude > or > > condescending, or anything of that nature. I only ask because I have > actual > > hands experience with this "feature" and have often wondered if there > > could be a potential work around( through code ). > > My experience is mostly from beating my head against the wall trying to > get this working, along with crawling through some of the device tree > "back-story", technical details, and kernel code. > > Basically, device tree is intended to be a *STATIC* definition of the > machine hardware available to the kernel at boot. Pretty much *ALL* > device tree does is store a bunch of values that can be retrieved via an > identifier (think INI file and you're not too far off). The overlay > stuff is all pretty much BeagleBone specific. > > Loading an overlay works fairly well because it is very similar in > concept and process to the kernel initialization...various kernel module > code gets run and other kernel modules may or may not already be present > or fully loaded. If your driver code can't deal with this, it's going > to be buggy in general use, regardless of whether or not you're trying > to load overlays. In a sense, loading a device tree overlay is very > much like simply extending system initialization for what could be a > _long_ time while a bunch of other code runs. :) > > Unloading an overlay, however, is a minefield of potential problems, > particularly since most of the ARM drivers weren't written with hot-plug > in mind. I'm not even sure most of the drivers can be unloaded at the > kernel level (hmm...I should go off and try to rmmod some of them). > > Anyway, true hotplug is a big-fat-hairy-can-of-worms, and pretty much > _none_ of the ARM ecosystem has been written with hot-plug in mind > (except for the bits that carry over from other systems, like USB and > PCI). It's not really surprising it crashes, it's just kind of > annoying. :) > > As for a work-around, I believe the saying goes: > > "There is no problem in computer science which cannot be solved by one > more level of indirection." > > -- > Charles Steinkuehler > char...@steinkuehler.net > > -- > 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 beagleboard+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
