Hi Sebestian, On Nov 6, 2013, at 10:31 PM, Sebastian Andrzej Siewior wrote: > On 06.11.13, Pantelis Antoniou wrote: >> Hi Sebastian, > Hi Pantelis, > >> It has been discussed. >> >> We are doing it because >> >> a) We tried to do it in u-boot and it has been a complete disaster. >> Regular users just can't handle bootloader updates. > > How so? The "additional" dtb piece was deleted by accident as part of > the u-boot upgrade? Do you maybe a link which describes the disaster? > You're assuming that bootloaders are anything like u-boot or barebox. In the field, especially on consumer products, bootloaders are custom one-off jobs that don't do much besides handing control to the kernel as soon as possible. Even when using u-boot, end users botch updates related to bootloader in such a way that systems end up RMAed. Ask Koen Kooi in the CClist about the messy details. >> b) It is similar to that. It was originally created for the beaglebone, >> which has a concept of capes (similar to Arduino shields). >> http://circuitco.com/support/index.php?title=BeagleBone_Capes >> Turns out it's really useful to anyone doing reconfigurable hardware too, >> so that's why FPGA people are thinking of using it. > > I am aware of this. My understanding is that those capes have hardware > information encoded in an eeprom behind i2c _and_ you can't or should > not replace capes at runtime. > Naive as I am I *assume* it should be easy to read this eeprom in u-boot > as part of the boot setup and extend the dtb before passing it to the > kernel. In case this works well, the problem here is a) ? > It is just better system design to have it all done in the kernel. Other people in the list can chime in, but it's hard to get a feel of the problem if you haven't dealt with it before. >> c) There are people that want to tinker with Linux based hardware boards >> but are not kernel developers. This gives them a way to do so without >> having to recompile the kernel and/or reboot while tinkering. > > I understand that they want to avoid reboot. But they still need to > recompile the device tree, don't they? Or does this allow to change the > HW description without knowing the syntax of .dts? > They understand the syntax of the DTS (barely). They can't hack compiling the kernel and updating it, not by a long shot. Not everyone is a kernel hacker (neither it needs be). Imagine people coming over from Arduino trying to hack a 4K board file to add support for the thing they're working on. >> Regards >> >> -- Pantelis > > Sebastian Regards -- Pantelis -- 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
