Re: [RFC] Dynamic boot logo

["hinko.kocevar@cetrtapot.si" <hinko.kocevar@cetrtapot.si>]

Rodolfo Giometti wrote:
> On Mon, Aug 06, 2007 at 09:53:24AM +0200, hinko.kocevar@cetrtapot.si wrote:
>> We would like to have this feature on my embedded system too! Currently 
>> we are using bitmap file converted to standard header file and then 
>> compiled in the kernel, which is not flexible at all.
> 
> Yes, I see.
> 
>> Maybe you could access the same flash memory from the Linux too - using 
>> either physical or virtual address space, eg. by I/O or memory mapping it.
> 
> Yes, I know, but _how_ can I do it? :) In u-boot is very easy but in
> Linux I still haven't found a good way to do so.

I'm almost certain that your architecture (whatever it may be) uses I/O 
and/or memory mapped memory for certain purposes. Best way to see how it 
is done would be to look at the drivers that are used on your architecture.
The bottom line is that ioremap() and friends could be used in 
combination with ioread/iowrite and/or readb/writeb primitives to map 
and later access the block of memory.

If you need some kernel programming pointers try reading Linux device 
drivers 3 (http://lwn.net/Kernel/LDD3/) or similar book. Also 
subscribing to the kernelnewbies mailing list could help with kernel basics.

> 
>> Another way could be using a dedicated kernel module for the job - eg. 
>> you compile the graphic support in the module and the when update is 
>> needed only module can be replaced in the file system leaving kernel 
>> intact (at least while kernel version does not change).
> 
> This is not solve the problem, you still need a compilation stage. I
> wish avoiding it. And, on the other hand, you cannot load a kernel
> module since you don't mount a root filesystem which is very late
> during boot.

You are right. I totally missed that part of the procedure although you 
could use initrd or initramfs for the job (but that does not remove the 
need to recompile the kernel when new module is being deployed).

Regards,
Hinko


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E-mail: hinko.kocevar@cetrtapot.si
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