[microblaze-uclinux] Loadable kernel modules support

[John Williams <jwilliams@xxxxxxxxxxxxxx>]

Hi folks,

I'm happy to announce that the Microblaze uClinux kernel now supports 
loadable kernel modules.

Thanks go to Jari (a Masters student here at UQ) for doing the work on this.

I've submitted the kernel patch to the CVS maintainers, it should be in 
soon.  One of the changes is to permit the existing drivers (gpio, 
ethernet and system_ace) to be created as loadable modules.  In the 
kernel config, you can now specify "M" for module, instead of just 
Yes/No for these drivers.

There's also a uClinux-dist patch that has the necessary changes to 
busybox/insmod.  I'll get that up on the website later today, when I 
update and clean out the Patches page.

Following is an example showing how it works:

/> lsmod 

Module                  Size  Used by    Not tainted 

xilinx_enet            18892   2

/> insmod xilinx_gpio 

Using 
/lib/modules/2.4.24-uc0/kernel/drivers/char/xilinx_gpio/xilinx_gpio.o
xgpio #0 at 0xFFFF5000 mapped to 0xFFFF5000 

Xilinx GPIO registered

/> gpio_test 

DIP SW: 11000011

/> lsmod 

Module                  Size  Used by    Not tainted 

xilinx_gpio             2348   0 

xilinx_enet            18892   2

/> rmmod xilinx_gpio

/> lsmod
Module                  Size  Used by    Not tainted 

xilinx_enet            18892   2

/> gpio_test 

Unable to open /dev/gpio 

pid 29: failed 256

Pretty cool huh? :)

Note here I've created/installed the ethernet driver as a loadable 
module as well.  The uClinux build process automatically handles the 
copying of kernel modules into the romfs/ subtree, and insmod knows 
where to look to find them.

One of the reasons this is interesting is because with drivers created 
as loadable modules, it allows us to pass parameters to them, so it 
makes things like dynamic IRQ and address map handling a lot easier.

Cheers,

John


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