[ARMedslack] A quick primer for the PI

stanley garvey stanley at stanleygarvey.com
Thu Sep 26 11:15:49 UTC 2013




On Sep 26, 2013 08:25 "Davide" <louigi600 at yahoo.it> wrote:

> 
> 
> >>I got a friend to lend me a PI for a week ...
> 
> 
> 
> 
> 
> >>I had a quick look at the community links for slackware on the PI
> >>but none really tell me what i want to know:
> >>what does the GPU look for in the SD ? (as fas as I know it's the
> >>GPU that loads stuff from SD into memory and then passes control to
> >>it)
> >>does it look for a second stage boot loader like a uboot image or
> >>does it load kernel and initrd ? (bootcode.bin)
> >>I'm supposing that the first partition (the dos one) is where this
> >>stuff should be put ?
> >>The content in there looks about right:
> 
> >>root at darkstar:/tmp# fdisk -l slackwarearm-14.0-8GB-20130623.img
> 
> >>Disk slackwarearm-14.0-8GB-20130623.img: 2558 MB, 2558967808 bytes
> >>4 heads, 32 sectors/track, 39046 cylinders, total 4997984 sectors
> >>Units = sectors of 1 * 512 = 512 bytes
> >>Sector size (logical/physical): 512 bytes / 512 bytes
> >>I/O size (minimum/optimal): 512 bytes / 512 bytes
> >>Disk identifier: 0x00007091
> 
> >> Device Boot Start End Blocks Id System
> >>slackwarearm-14.0-8GB-20130623.img1 32 97663 48816 c W95 FAT32 (LBA)
> >>slackwarearm-14.0-8GB-20130623.img2 97664 878847 390592 82 Linux
> >>swap
> >>slackwarearm-14.0-8GB-20130623.img3 878848 15751167 7436160 83 Linux
> >>root at darkstar:/tmp# echo $((32 * 512))
> >>16384
> >>root at darkstar:/tmp# losetup -o 16384 /dev/loop0
> >>slackwarearm-14.0-8GB-20130623.img
> >>root at darkstar:/tmp# modprobe vfat
> >>root at darkstar:/tmp# mount /dev/loop0 /mnt/floppy/
> >>root at darkstar:/tmp# ls /mnt/floppy/
> >>COPYING.linux* config-raspberrypi-3.2.27* start.elf*
> >>LICENCE.broadcom* config.txt* start_cd.elf*
> >>System.map-raspberrypi-3.2.27* fixup.dat* zImage-raspberrypi-3.2.27*
> >>bootcode.bin* fixup_cd.dat*
> >>cmdline.txt* initrd-raspberrypi.img*
> >root at darkstar:/tmp#
> 
> 
> >>I plan to play a little with a miniroot so I won't need an 8Gb SD :)
> 
> >Hi David,
> Hi Dave ;) 
> >The GPU looks for bootcode.bin, which looks for and loads loader.bin.
> >Loader.bin reads in config.txt (to configure the hardware) and loads
> >start.elf (the GPU binary blob). Once it has configured the hardware,
> >it then >loads kernel.img, and feeds it the contents of cmdline.txt.
> 
> But on the readymade image from
> http://stanleygarvey.com/slackwarearm_rpi/index.php there is no
> loader.bin in the dos partition !
> Is there something wrong with this image or is loader.bin optional ?
> > Hi Davide, ther is nothing wrong with the image, I use it at home,
> > it could be that loader bin is a new addition to the Fat32 boot
> > partitionfor Debian variants. the boot layout I use has not changed
> > since last Christmas.
> 
> >So you have to have bootcode.bin, loader.bin, config.txt, start.elf,
> >kernel.img, and cmdline.txt, then if you load a ramdisk image in the
> >cmdline.txt file you need the ramdisk image file.
> 
> > yes
> 
> Is the initrd loading governed by config.txt ?
> > yes
> 
> I see in there ramfsfile=initrd-raspberrypi.img
> Can I change that manualy with vi and load a different initrd ? or
> comment it out to not load an initrd at all ?
> 
> > Yes you can edit the file with vi and load a different initrd. It is
> > commented out in my config.txt as it is not required to boot a
> > running system. initrd-raspberrypi.img is the installer, It has been
> > left there so you can reinstall if you wish, it is a
> > versatile-initrd that has been modified with a modified version of
> > the mk-tegra.sh.
> 
> When is the HDMI output initiated ?
> 
> >Before the system comes up as the GPU boots the system.
> 
> > if you ate looking for a mini root try the installer image, it is
> > 1GB and is the standard slackwarearm installer so has busybox and
> > other stuff. you won't be able to install a full system on 1GB the
> > 3rd partition is a stub and should be deleted and recreated to use
> > the remaining space on whatever size card you have before stating
> > 'setup'. you may be able to get a base slackwarearm systm (a)(ap)
> > series on a 4GB card.
> Hope that helps,
> Stanley.
> 
> 
> 
> 
> 
> 
> 
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