[Patch] i386: remove 'usedac' kernel parameter

[Patch] i386: remove 'usedac' kernel parameter

[Amerigo Wang]

It is scheduled to be removed.

Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Glauber Costa <gcosta@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>

---
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 591e944..8c895f6 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -291,13 +291,6 @@ Who:	Michael Buesch <mb@bu3sch.de>
 
 ---------------------------
 
-What:	usedac i386 kernel parameter
-When:	2.6.27
-Why:	replaced by allowdac and no dac combination
-Who:	Glauber Costa <gcosta@redhat.com>
-
----------------------------
-
 What: print_fn_descriptor_symbol()
 When: October 2009
 Why:  The %pF vsprintf format provides the same functionality in a
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index afcc58b..2f76c7b 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -210,10 +210,6 @@ static __init int iommu_setup(char *p)
 			forbid_dac = 0;
 		if (!strncmp(p, "nodac", 5))
 			forbid_dac = 1;
-		if (!strncmp(p, "usedac", 6)) {
-			forbid_dac = -1;
-			return 1;
-		}
 #ifdef CONFIG_SWIOTLB
 		if (!strncmp(p, "soft", 4))
 			swiotlb = 1;

Re: [Patch] i386: remove 'usedac' kernel parameter

[FUJITA Tomonori]

On Wed, 9 Dec 2009 01:25:48 -0500
Amerigo Wang <amwang@redhat.com> wrote:

> It is scheduled to be removed.
> 
> Signed-off-by: WANG Cong <amwang@redhat.com>
> Cc: Glauber Costa <gcosta@redhat.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> 
> ---
> diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
> index 591e944..8c895f6 100644
> --- a/Documentation/feature-removal-schedule.txt
> +++ b/Documentation/feature-removal-schedule.txt
> @@ -291,13 +291,6 @@ Who:	Michael Buesch <mb@bu3sch.de>
>  
>  ---------------------------
>  
> -What:	usedac i386 kernel parameter
> -When:	2.6.27
> -Why:	replaced by allowdac and no dac combination
> -Who:	Glauber Costa <gcosta@redhat.com>
> -
> ----------------------------
> -

I'm not sure about the above description, I'm not against removing
this option though.

IIUC, the usedac option enables us to stop via_no_dac() setting
forbid_dac to 1. That is, someone who uses VIA bridges can use DAC
with this option even if some of VIA bridges seem to be broken about
DAC. I can't see how we can do the same thing with "allowdac" and
"nodac" combination.

Re: [Patch] i386: remove 'usedac' kernel parameter

[Cong Wang]

FUJITA Tomonori wrote:
> On Wed, 9 Dec 2009 01:25:48 -0500
> Amerigo Wang <amwang@redhat.com> wrote:
> 
>> It is scheduled to be removed.
>>
>> Signed-off-by: WANG Cong <amwang@redhat.com>
>> Cc: Glauber Costa <gcosta@redhat.com>
>> Cc: Ingo Molnar <mingo@elte.hu>
>>
>> ---
>> diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
>> index 591e944..8c895f6 100644
>> --- a/Documentation/feature-removal-schedule.txt
>> +++ b/Documentation/feature-removal-schedule.txt
>> @@ -291,13 +291,6 @@ Who:	Michael Buesch <mb@bu3sch.de>
>>  
>>  ---------------------------
>>  
>> -What:	usedac i386 kernel parameter
>> -When:	2.6.27
>> -Why:	replaced by allowdac and no dac combination
>> -Who:	Glauber Costa <gcosta@redhat.com>
>> -
>> ----------------------------
>> -
> 
> I'm not sure about the above description, I'm not against removing
> this option though.
> 
> IIUC, the usedac option enables us to stop via_no_dac() setting
> forbid_dac to 1. That is, someone who uses VIA bridges can use DAC
> with this option even if some of VIA bridges seem to be broken about
> DAC. I can't see how we can do the same thing with "allowdac" and
> "nodac" combination.


Hmm, yes, right, I missed this point.

Thanks!