On Sat, Jul 11, 2015 at 11:29 AM, QIAO YANG <yangqiao0...@me.com> wrote: > Hi, > > I tried to retrieve atag command lines but I've got wired problems: > I ran a quick scan for atags, start from 0x100, and I've got an output like > : > > [ATAG_CORE] flags: 0, pagesize: 0, rootdev: 0 > [ATAG_MEM] size: 8000000, start: 0 > [ATAG_CMDLINE] found: > dma.dmachans=0x7f35 bcm2708_fb.fbwidth=656 bcm2708_fb.fbheight=416 > bcm2708.boardrev=0xf bcm2708.serial=0x8247b4bb smsc95xx.macaddr=B8s > start addr:12C > size : 2E616D64 > didn't find [ATAG_NONE] > > which told me that: > 1. The start address of atag cmdline is 0x12C > 2. The size of this tag is 0x2E616D64 > The size of the tag is abnormal. > From the output, it seems that I only retrieved part of the cmdline. > Perhaps you have messed up the field layout or somehow gotten the wrong field offsets?
> > I've also tried to use the mailbox interface to get the cmdline. what I've > got is exactly the same part of string without error reponse. Even if I > tried to print the following characters, they are all empty. > I think that the atags area maybe rewritten in some way but I didn't managed > to figure out. What bothers me most is the length of the tag, because the > tag id is correct, part of the value is readable, there's no reason that the > data between them is incorrect. The atag area should be written by > videocore, who load the cmdline.txt where we can add additional lines. > > > Besides I've also got a question that how can I get the value of r2 that > passed by bootloader to kernel image? It should store the value of start > address of ATAG or the magic of device tree. What I've found in linux is > that there is a function like init( *param), which is called when loading > the kernel, and the function get the value of r2 as the parameter passed to > it. I wonder how can I get this value, though by default the atag starts > from 0x100. > Check in the BSP boot-up code (usually in the bsp subdirectory, start.S file). > > If it takes too long to implement the feature (atag, device tree ....), I've > got other ways to detect if a hdmi device is present and then disable/enable > the graphic console. If I'm allowed to pass the atag/device tree > implementation. > Can you clarify this statement? What "other ways" do you mean? > > Best wishes. > > _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
