Re: Why is AHA152X_CS !64BIT?

[Jiri Slaby <jslaby@suse.cz>]

On 09/08/2010 12:10 AM, James Bottomley wrote:
> On Tue, 2010-09-07 at 14:48 -0700, Randy Dunlap wrote:
>> On 09/07/10 14:41, Randy Dunlap wrote:
>>> On 09/07/10 14:12, Konrad Rzeszutek Wilk wrote:
>>>> On Monday 30 August 2010 07:13:17 Boaz Harrosh wrote:
>>>>> On 08/23/2010 10:59 PM, Jiri Slaby wrote:
>>>>>> Hi,
>>>>>>
>>>>>> I see that the aha152x driver for pcmcia is marked as unsupported on
>>>>>> 64bit. But I also see a patch [1] which removes the restriction based on
>>>>>> user's testing in bugzilla [2].
>>>>>>
>>>>>> Is there a reason why it would have to be marked as !64BIT? I'm asking
>>>>>> because there is an opensuse user with this card who updated to 64-bit
>>>>>> distro and lost this driver thereafter.
>>>>>>
>>>>>> [1] http://kerneltrap.org/mailarchive/linux-scsi/2010/3/6/6832393
>>>>>> [2] https://bugzilla.kernel.org/show_bug.cgi?id=14333
>>>>>>
>>>>>> thanks,
>>>>>
>>>>> If memory serves correctly, it might be that you need more then 4 Gbyte
>>>>> of memory installed to exercise the bug, something about IO bouncing
>>>>> addresses > 4G.
>>>>
>>>> If the machine is using SWIOTLB, then the bounce buffer would be activated. By 
>>>> default if your machine has more than 4GB compiled under x86_64 the SWIOTLB 
>>>> is turned on - but if you have an Intel/AMD IOMMU it gets turned off. Which 
>>>> is OK as the Intel/AMD IOMMUs would handle the 4GB restricted devices. So as 
>>>> long as the driver has pci_dma_mask_set.
>>>>
>>>> Looking at the git gui blame tool history, the reason that was added was 
>>>> for 'allow drivers to be built non-modular'.
>>>
>>> 023ae619 (Robert P. J. Day  2007-03-26 16:06:45 -0400 14) 	depends on !64BIT
>>>
>>> That commit just removed the "depends on m" part:
>>>
>>> -	depends on m && !64BIT
>>> +	depends on !64BIT
>>>
>>>
>>>> So, does this driver build if you make it non-modular?
>>>
>>> It shouldn't since it still depends on !64BIT.
>>>
>>> I expect someone thought or had evidence that the driver was not 64-bit clean.
>>>
>>> Is the bitkeeper kernel repo still visible somewhere?
>>> Looks like we would need to look at it for patch history that far back.
>>>
>>
>> http://linux.bkbits.net:8080/linux-2.6/?PAGE=cset&REV=3fe0bc41KO89ooP68UcrHEMVVAfDnw
>>
>> but it doesn't quite make sense to me.  Sure, no ISA on x86_64, but that does not
>> mean no PCMCIA on x86_64.
> 
> Actually, the patch is this one:
> 
> http://permalink.gmane.org/gmane.linux.scsi/5835
> 
> The complaint is that the driver spews warnings on a 64 bit compile, so
> it's likely not 64 bit clean.

As I wrote few minutes ago, there is only one which is in print. And I
cannot find anybody fixing anything similar since 2.1.

So can we enable it on 64-bit when we have two reports it works on
64-bit? (Is it still maintained? MAINTAINERS says so...)

thanks,
-- 
js
suse labs