Re: Porting Kernel / Drivers to BeagleBoard

Hi Jim,

Jim Burnes wrote:
> I've been digging through the architecture and platform-specific code 
> for Haiku.  I made a bunch of notes which I'll post later.  Maybe if I 
> collect all of my notes into something intelligible I could turn it 
> into a Haiku Guide ("Porting Haiku").
Another option would be to blog about your progress (even about figuring 
stuff out) on the site, that's a nice intermediate way of not having to 
create a real document but still store and share the information 
collected....
> I've seen a number of Linux Porting guides.  Since Haiku and BeOS were 
> intended to be highly responsive for interactive multimedia streaming, 
> embedded Haiku could turn out to be a real hit in that market.  Most 
> embedded devices don't have huge software compatibility requirements 
> since they are often developed from scratch.  That means Haiku could 
> achieve significant penetration into these markets if we get one port 
> working well, with special attention to embedded needs.
BeOS itself was used in several media-specific special-purpose systems, 
TuneTracker is probably one of the last ones alive, though I could be 
wrong....
>
> I have a few questions after browsing through the source code.  (I'm 
> sure I'll have more)
>
> 1. Were you implying that we don't even need the Haiku boot loader and 
> could substitute u-boot -- or did you simply mean that we'd have to 
> interface u-boot to the Haiku boot loader?
U-Boot has support for loading binaries/datafiles into memory and 
executing them, so yes, it could even be possible to reuse that just to 
get started....
> 2. I've been trying to find how initial device settings are encoded at 
> compile-time.  It seems that there are several different ways:
>
>    a) the bad way:  someone hard codes it into the .c module
>    b) a better way: someone hard codes it into platform specific .h file
>    c) an even better way: in 
> /src/add-ons/kernel/drivers/graphics/nvidia/nvidia.settings for 
> specific add-on devices
>    d) best way: some sort of kernel.settings file as above which can 
> be overridden by boot loader arguments
>
> 3. I noticed that settings files are present in 
> /home/config/kernel/drivers/  ...   /something.settings.  Are these 
> generated at image build time or afterwards by the kernel?
Image generation time.
>
> 4. There's a get_driver_settings call that picks them up from 
> somewhere (a file apparently).  What if there's no file system?  Will 
> it pick them up from boot time arguments? 
The normal Haiku/BeOS bootloader has a way of specifying these settings, 
in the bootmenu. No way to save them, other then storing them on (some 
kind of) filesystem though AFAIK.
>
> 5. This just shows how little I've used Haiku lately, but is there a 
> way of specifying kerrnel arguments on the boot loader command line 
> like you do in linux?  eg: linux noapm acpi=off
See the above.

HTH,

Ithamar.

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