Re: [2.6 patch] mark virt_to_bus/bus_to_virt as __deprecated oni386

[linux-os (Dick Johnson)]

On Wed, 19 Apr 2006, Arjan van de Ven wrote:

> On Wed, 2006-04-19 at 14:21 -0400, linux-os (Dick Johnson) wrote:
>> On Wed, 19 Apr 2006, Adrian Bunk wrote:
>>
>>> On Wed, Apr 19, 2006 at 08:13:55AM +0300, Muli Ben-Yehuda wrote:
>>>> On Wed, Apr 19, 2006 at 12:07:15AM +0200, Adrian Bunk wrote:
>>>>> virt_to_bus/bus_to_virt are long deprecated, mark them as __deprecated
>>>>> on i386.
>>>>
>>>> You should probably update Documentation/ while you're at it.
>>>
>>> Which file under Documentation/ are you referring to?
>>>
>>>> Also, IIRC Xen uses virt_to_phys to return guest physical addresses
>>>> and virt_to_bus to return machine physical addresses, so the
>>>> difference is useful at least in some scenarios.
>>>
>>> Solving this should be easy.
>>>
>>> And this still doesn't make it right for architecture independent
>>> drivers to use virt_to_bus/bus_to_virt.
>>
>> Then what would you use to return the proper bus address to put
>> into a DMA scatter list and, conversely, how would you convert
>> those bus addresses into something a virtual mode CPU could
>> access?  These macros used to be the link that made such driver
>> coding architecture independent. You cannot just claim that
>> one can't make such conversions anymore. The CPU uses virtual
>> addresses and the DMA uses physical (bus) addresses. Do we
>> throw away DMA altogether?
>
> since a long time the kernel has proper dma mapping API's for this, in
> 2.4 it's pci specific in 2.6 it's generic and bus agnostic.
>

Yeah. Somebody finally let you put a NULL in place of the PCI
structure pointer so you didn't have to write a lot of dummy
code. Now, on ix86 devices, instead of |= PAGE_OFFSET or inverse,
one needs to add all that PCI code. Go figure. Bloatware.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.15.4 on an i686 machine (5589.53 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_


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