Hello Wojciech, On Mon, 16 Nov 2015 13:09:43 +0100, Wojciech Zabolotny <wza...@gmail.com> wrote: > 2015-11-16 11:52 GMT+01:00 Albert ARIBAUD <albert.u.b...@aribaud.net>: > > Hello Wojciech, > > > > On Mon, 16 Nov 2015 10:42:50 +0100, Wojciech Zabolotny > > <wza...@gmail.com> wrote: > >> Hi, > >> > >> I need to use U-Boot (or barebox) as a bootloader in a Raspberry Pi > >> based system to extend booting flexibility. > >> The problem however is that certain kernel boot arguments are prepared > >> by the previous stage bootloader (start.elf) > >> basing on the properties of the individual board. > >> For example in one of the boards I use, the kernel command line when a > >> standard kernel is booted, looks as follows (MAC address and serial > >> number are partially masked for privacy): > >> > >> dma.dmachans=0x7f35 bcm2708_fb.fbwidth=720 bcm2708_fb.fbheight=480 > >> bcm2708.boardrev=0xd bcm2708.serial=0x6f15XXXX > >> smsc95xx.macaddr=B8:27:EB:XX:XX:XX bcm2708_fb.fbswap=1 > >> sdhci-bcm2708.emmc_clock_freq=250000000 vc_mem.mem_base=0x1ec00000 > >> vc_mem.mem_size=0x20000000 console=ttyAMA0 root=/dev/mmcblk0p2 > >> rootwait > >> > >> Only the "console=ttyAMA0 root=/dev/mmcblk0p2 rootwait" is provided by > >> the user (in the cmdline.txt file). The rest is generated by the > >> start.elf. > >> > >> Of course when I boot the u-boot.bin instead of zImage, the same > >> parameters are passed to it, but the U-Boot is not able to read them > >> and to pass them to the finally booted kernel. > >> As U-Boot shares a lot of code with the Linux kernel it should be > >> possible to add necessary functions. > >> It could be useful in all applications where U-Boot is used as an > >> additional stage in the boot chain e.g., to add new booting > >> functionalities (booting from the network, booting from the flash disk > >> etc.). > >> > >> I have found a nice description, how the paremeters are passed in ARM > >> architecture: > >> http://www.simtec.co.uk/products/SWLINUX/files/booting%5Farticle.html > >> but of course the solution should be probably portable (or implemented > >> for each platform independently with unified API). > > > > Not sure what kind of answer you're asking for here. Do you want to > > know if what you're suggesting is feasible? Are you looking for someone > > to implement it? Are you going to implement it yourself but asking for > > feedback? > > > >> -- > > > > (aside: if the above should be a signature delimiter, then it lacks a > > space after the dashes) > > > > Amicalement, > > -- > > Albert. > > Dear Albert, > > Yes the first question is if this feature is feasible.
In software, just about anything is feasible; ask any PHB. :) Specifically, catching information passed to U-Boot's entry point is something that e.g. OMAPs do already. It is probably not going to be portable, though, because the passing method is inherently specific to your platform and pre-U-Boot loader. > If yes, then I'd like to propose such functionality as a possible improvement. > I think that may be more people interested in such a feature. > > I'll appreciate any sugestions/pointers regarding the possible implementation. > > Probably I can try to implement it. Of course if there are other > interested users > who can do it, I'll be definitely happy to discuss that with them. Best is that you post a patch with a working implementation which can be build above current u-boot/master branch; people interested in it will comment. > Regards, Amicalement, -- Albert. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot