On 9/23/2015 2:18 AM, Rick Mann wrote: > What are the "universal" DTBs, like cape-universal-00A0.dtbo or > univ-emmc-00A0.dtbo?
The "universal" DTBs are intended to allow user-mode changes to the pin configurations at run-time. This is very handy on kernels that do not support dynamic changes to the device tree (ie: 3.14), but is also useful for 3.8 and 4.x kernels with cape manager support. The idea is basically that you enable most of the available hardware (UARTs, PWM, GPIO, etc) and use the pinmux helper kernel module to make low-level pin settings available via sysfs. That way, you can modify the pin functions without having to load a new DT overlay. This allows some combinations that would be "illegal" or hard to implement without writing your own custom device tree (which is non-trivial for most folks). For example, if you need a UART but only require the Rx line and want to use the Tx line as a GPIO, you'd typically have to craft your own custom device tree. With the universal overlay, you can just set the Rx line to the UART mode, and the Tx line to GPIO, since both functions are already enabled and the pinmux helper module lets you select the pin mode at run-time. -- Charles Steinkuehler [email protected] -- 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.
