Re: [Xenomai-core] Comedi buffer management.

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Alexis Berlemont wrote:
> Hi Gilles,
> 
> Sorry for answering so late. I was unable to regularly check my private mails 
> the last week; I missed yours.
> 
>> I commited in trunk a fix of Xenomai heap management for the highmem
>> case. What the patch does is essentially replacing __va_to_kva (which
>> does not work correctly with highmem) with vmalloc_to_page, which is
>> available on all linux versions Xenomai supports.
>>
>> However, I found that comedi buffer management also uses __va_to_kva. We
>> can fix SetPageReserved and ClearPageReserved easily to use
>> vmalloc_to_page, however, I do not see what pg_list is used for, so do
>> not really know how to fix it. Here is a proposed patch:
> 
> If I remember well, pg_list may be used by some PCI/PCIe DMA components which 
> can dump acquired data to physically non-contiguous buffers. In such cases, 
> the driver has to provide a list of the pages addresses into which the DMA 
> controller can trigger shots.
> 
> Many thanks for your fix. 

No problem, really, I actually did not fix pg_list. It will not work
with highmem. What do the DMA needs? physical adresses? Then you need to
replace page_address(vmalloc_to_page(vaddr)) with
page_to_phys(vmalloc_to_page(vaddr))

Or you may store the struct page, and let the drivers do what they want
with it.

-- 
                                                 Gilles.