[Buildroot] u-boot .img rootfs

[Buildroot] u-boot .img rootfs

[H Hartley Sweeten]

Hello all,

I have been using Buildroot to create a rootfs.ext2.gz that works great
with RedBoot.

I have a new board that uses U-Boot as the bootloader and it wants some
kind of .img file for the rootfs.  Can this be created using Buildroot? Do I
need to do something after the rootfs.ext2.gz is created to make the .img
file?

Any pointers?

Thanks,
Hartley

[Buildroot] u-boot .img rootfs

[Thomas Petazzoni]

Le Mon, 5 Mar 2012 20:00:57 -0600,
H Hartley Sweeten <hartleys@visionengravers.com> a ?crit :

> I have been using Buildroot to create a rootfs.ext2.gz that works
> great with RedBoot.
> 
> I have a new board that uses U-Boot as the bootloader and it wants
> some kind of .img file for the rootfs.  Can this be created using
> Buildroot? Do I need to do something after the rootfs.ext2.gz is
> created to make the .img file?

Do you have more details, because .img is very generic. Do you have a
pointer to your specific U-Boot configuration? Can you just show why
you think U-Boot needs such as file?

Thanks,

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

[Buildroot] u-boot .img rootfs

[H Hartley Sweeten]

On Tuesday, March 06, 2012 3:48 AM, Thomas Petazzoni wrote:
> Le Mon, 5 Mar 2012 20:00:57 -0600, H Hartley Sweeten <hartleys@visionengravers.com> a ?crit :
>
>> I have been using Buildroot to create a rootfs.ext2.gz that works
>> great with RedBoot.
>> 
>> I have a new board that uses U-Boot as the bootloader and it wants
>> some kind of .img file for the rootfs.  Can this be created using
>> Buildroot? Do I need to do something after the rootfs.ext2.gz is
>> created to make the .img file?
>
> Do you have more details, because .img is very generic. Do you have a
> pointer to your specific U-Boot configuration? Can you just show why
> you think U-Boot needs such as file?

This is the first U-Boot system I have worked with so I don't have a lot
of details.

I know that that this works:

SIM.ONE> tftp c0200000 uImage
TFTP from server 192.168.0.84; our IP address is 192.168.0.79
Filename 'uImage'.
Load address: 0xc0200000
Loading: #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         ###################################################
done
Bytes transferred = 1923792 (1d5ad0 hex)
SIM.ONE> iminfo

## Checking Image at c0200000 ...
   Image Name:   Linux-3.2.5
   Image Type:   ARM Linux Kernel Image (uncompressed)
   Data Size:    1923728 Bytes =  1.8 MB
   Load Address: c0008000
   Entry Point:  c0008000
   Verifying Checksum ... OK

But, when I try the ramdisk.gz file (rootfs.ext2.gz) I get this:

SIM.ONE> tftp c8000000 ramdisk.gz
TFTP from server 192.168.0.84; our IP address is 192.168.0.79
Filename 'ramdisk.gz'.
Load address: 0xc8000000
Loading: #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #################################################################
         #####################################################
done
Bytes transferred = 2266236 (22947c hex)
SIM.ONE> iminfo

## Checking Image at c8000000 ...
   Bad Magic Number

The only things I have found about the U-Boot image file mentions using 'mkimage' to create
the file using a command like these examples:

mkimage -T ramdisk -C gzip -n 'Test Ramdisk Image' -d ramdisk.img.gz uRamdisk
mkimage -A sh -O linux -T ramdisk -a 0x8C800000 -n "ST40 Linux ramdisk" -d initrd.img /export/ramdisk.ub

My guess the uRamdisk file is the same format as the uImage file used for the kernel. But,
I'm not sure what the format of the ramdisk.img.gz or initrd.img files are.

I do see there is a uboot-mkimage package available in Debian. It says this about it:

---

This package contains the mkimage utility, which encapsulates a compressed "uImage"
Linux kerel image with header information, CRC32 checksum, etc, for use with the
U-Boot bootloader.
 
mkimage can also be used to create ramdisk images for use with U-Boot, either separated
from the Linux kernel image, or combined into one file. mkimage encapsulates the images
with a 64 byte header containing information about target architecture, operating system,
image type, compression method, entry points, time stamp, CRC32 checksums, etc.

---

Regards,
Hartley

[Buildroot] u-boot .img rootfs

[Thomas Petazzoni]

Le Tue, 6 Mar 2012 10:48:10 -0600,
H Hartley Sweeten <hartleys@visionengravers.com> a ?crit :

> The only things I have found about the U-Boot image file mentions
> using 'mkimage' to create the file using a command like these
> examples:
> 
> mkimage -T ramdisk -C gzip -n 'Test Ramdisk Image' -d ramdisk.img.gz
> uRamdisk mkimage -A sh -O linux -T ramdisk -a 0x8C800000 -n "ST40
> Linux ramdisk" -d initrd.img /export/ramdisk.ub
> 
> My guess the uRamdisk file is the same format as the uImage file used
> for the kernel. But, I'm not sure what the format of the
> ramdisk.img.gz or initrd.img files are.

Yes, you have to pass the ext2.gz file through mkimage before giving it
to U-Boot, in order to generate a ramdisk image that U-Boot can
understand and load into memory.

However, this way of doing ramdisks is more or less deprecated,
initramfs have been the norm since quite some years now.

Best regards,

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com