On Thu, Sep 8, 2016 at 5:33 PM, Rob Herring <robh+dt@xxxxxxxxxx> wrote: > On Thu, Sep 8, 2016 at 4:15 PM, Dmitry Shmidt <dimitrysh@xxxxxxxxxx> wrote: >> On Thu, Sep 8, 2016 at 2:08 PM, Frank Rowand <frowand.list@xxxxxxxxx> wrote: >>> What problem(s) are you trying to solve with this? >> >> Currently the Linux kernel doesn't provide a way for boot time >> selection of different possible board configurations, when the board >> peripherals are specified via Device Tree. > > Well, the kernel does provide a way. For different h/w you give it a > different h/w description (i.e. dtb). The issue is having multiple > dtbs for mostly similar h/w is a PIA. Agreed. > Also, it can be argued this should remain a bootloader problem. For > the LCD case, the bootloader is going to need that information to > support a splash screen. libfdt is learning how to apply overlays on > flat trees. I can imagine in many cases like devboards with various attached shields/mezzanines the bootloader doesn't (and likely can't) have this ability. >>> What is the use case? >> >> It is usually useful for development board when you can use >> different peripherals. For example you want to use special >> LCD panel. Using it will go on account of other stuff like GPIOs, >> so you don't want it all the time. And it is not convenient to >> apply new patches and to recompile the kernel. And this code >> allows to choose LCD panel configuration from command line. > > If you can figure out how to change the command line, then you can > just change the dtb. At least for how Android boot works, those aren't > really changed separately. Ehh.. that's not so simple. The dtb is often appended to the kernel on Android devices. Changing the boot arguments is much simpler to do. thanks -john -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
