[yocto] i486sx machine porting from oe-classic

[Mark Hatle]

On 1/20/12 8:07 AM, Andrea Galbusera wrote:
> Hi,
>
> In oe-classic there used to be a machine configuration for an i486sx
> based machine called vortex86sx. In the past I was successful in
> building a running image for such a target. Since I'd like to make a
> new system based on vortex, my goal is to leverage the whole Yocto
> Project infrastructure and port that old configuration to a BSP layer.
> This will save me a lot of time in supporting developers with SDKs and
> so.
>
> Since I could not find any BSP based on hardware older than i586 in
> recent Yocto trees, I'm concerned about this. Do you know of any
> obstacle in doing such a port? I'm mainly interested in building
> images with no graphics for that target: core-image-minimal is a
> reasonable reference for me.
>
> My plan was to initially lay out a new BSP by following guidelines
> from Development Manual and BSP Guide. Then, what I suspect to be a
> little trickier for my expertise, is the porting of the original
> tune-i486sx.inc file to the current Yocto infrastructure. Is there any
> document I can leverage to map the variables defined in the
> oe-classic's syntax to the current ones for such a machine
> configuration file?

A few things you will need.. a tune file for the CPU, and a tune file for the 
machine/bsp... and you'll have to make sure that eglibc/Linux can still run on 
that machine.

I know a while back some changes were made to the GNU toolchain, include gcc to 
change default optimization levels and such, I don't know if this negatively 
impacted the ability to generate i486 compatible code.

> The original i486 tune file was defining the following:
>
> TARGET_ARCH = "i486"
> TARGET_CC_ARCH = "-march=i486"
> PACKAGE_EXTRA_ARCHS = "486sx"
> BASE_PACKAGE_ARCH = "486sx"
> FEED_ARCH = "${BASE_PACKAGE_ARCH}"
>
> Are they still valid variables? Do I need any more?

Variables have changed.  The following is likely what you want (not tested of 
course) meta/conf/machine/include/tune-i486.inc (based off of tune-i586):

DEFAULTTUNE ?= "i486"
TUNE_PKGARCH_TMP = "${@bb.utils.contains("TUNE_FEATURES", "m32", "x86", 
"x86_64", d)}"
TUNE_PKGARCH ?= "${@bb.utils.contains("TUNE_FEATURES", "i486", "i486", 
TUNE_PKGARCH_TMP, d)}"

require conf/machine/include/ia32/arch-ia32.inc

# Extra tune features
TUNEVALID[i486] = "Enable i486 specific processor optimizations"
TUNE_CCARGS += "${@bb.utils.contains("TUNE_FEATURES", "i486", "-march=i486", "", 
d)}"

# Extra tune selections
AVAILTUNES += "i486"
TUNE_FEATURES_tune-i486 ?= "${TUNE_FEATURES_tune-x86} i486"
BASE_LIB_tune-i486 ?= "lib"
PACKAGE_EXTRA_ARCHS_tune-i486 = "${PACKAGE_EXTRA_ARCHS_tune-x86} i386 i486"

--Mark

> Thank you in advance. Regards,
> Andrea
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