Re: [Xenomai-core] [PATCH, RFC] Make ioremap'ed memory available through rtdm_mmap_to_user()

[Jan Kiszka <jan.kiszka@domain.hid>]

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Stelian Pop wrote:
> [Sorry for the delay, I was quite busy those days and unable to test the
> patch...]
> 
> Le mardi 19 septembre 2006 à 17:34 +0200, Jan Kiszka a écrit :
>>> Or maybe we should lower the API level a little bit, and let the user
>>> specify the physical address of the mapping instead of the virtual
>>> one....
>> How would this help? You still need the virtual address for VMA blocks
>> in order to collect the pages.
> 
> Actualy we need both the virtual address (for vmalloc case) and the
> physical address (for ioremap case).
> 
>> +    if (mmap_data->mem_type == RTDM_MEMTYPE_VMALLOC) {
> [...]
> 
> This still won't work because for RTDM_MEMTYPE_IOREMAP
> virt_to_phys((void *)vaddr) doesn't return the physical address.
> 
> So we still need to either:
> 	a) walk the vmlist struct to find out the needed vm->phys_addr (which
> will probably won't work in 2.4, or even in earlier 2.6 kernels)

Sounds fragile, indeed.

> 
> 	b) pass both the physical and the virtual adresses in the
> rtdm_mmap_to_user prototype (the physical address would be used only
> when RTDM_MEMTYPE_IOREMAP is specified)

Hmm, a bit ugly, this long argument list.

> 
> 	c) make 'src_addr' be a virtual address in some cases, and a physical
> address in ioremap case.

That's so far the cleanest solution in my eyes.

> 
> 	d) make a special rtdm_mmap_iomem_to_user() function...

Also an option. Specifically, it wouldn't break the existing API... What
about rtdm_iomap_to_user? Would you like to work out a patch in this
direction?

Jan


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