[PATCH v3 3/4] ipq40xx: fix compatibility with linux-atm tools

[Sergey Ryazanov]

Hi Andre, Martin,

On 13.01.2025 14:17, Andre Heider wrote:
> On 13/01/2025 9:17 am, Martin Schiller wrote:
>> On 2025-01-12 15:09, Sergey Ryazanov wrote:
>>> atm_qos struct should be the same both for user and kernel spaces. Via
>>> the __SO_ENCODE() macro it is used to define the SO_ATMQOS socket IOC.
>>>
>>> During the VRX518 support introduction, the atm_trafprm sturct nested
>>> into the atm_qos stucture was update with newer fields that are
>>> referenced by the ATM TC layer of the VRX518 TC driver. These new fields
>>> are intended to communicate information for extra traffic classes
>>> supported by the driver. But we are still using vanilla kernel headers
>>> to build the toolchain. Due to the atm.h header incoherency br2684ctl
>>> from linux-atm tools is incapable to configure the ATM bridge netdev:
>>>
>>>   br2684ctl: Interface "dsl0" created sucessfully
>>>   br2684ctl: Communicating over ATM 0.1.2, encapsulation: LLC
>>>   br2684ctl: setsockopt SO_ATMQOS 22 <-- EINVAL errno
>>>   br2684ctl: Fatal: failed to connect on socket; File descriptor in 
>>> bad state
>>
>> Hmmm... I have fixed this problem in the past by including the
>> "user_headers". See commit e53ed6af8744 (“linux-atm: use target specific
>> kernel headers”) [1]. Felix suggested this to me in [2].
>> Does this no longer work?
> 
> Good question, I didn't know about that patch.

Me too. As it was mentioned in cover letter, I've faced the ATM bridge 
issue on the latest stable release - 23.05.5. And the e53ed6af87 
("linux-atm: use target specific kernel headers") commit was introduced 
after the branching and was never backported:

$ git log --oneline -n3 master package/network/utils/linux-atm/
3e024022c3 linux-atm: fix build with GCC 14
e53ed6af87 linux-atm: use target specific kernel headers
9aa3d5b345 linux-atm: Include linux/sockios.h for SIOCGSTAMP

$ git log --oneline -n2 openwrt-23.05 package/network/utils/linux-atm/
9aa3d5b345 linux-atm: Include linux/sockios.h for SIOCGSTAMP
806354ab53 linux-atm: Fix compile warning

I developed the extra fields disabling patch for the stable release and 
then rebased. And then in V3 extended it to drop the Lantiq's ATM hacks 
entirely.

BTW, I checked the Martin's fix in the latest master just now. It works 
and picks the correct atm.h from the patched kernel.

> At least on ipq40xx there's nothing writing the custom classes to qos- 
>  >txtp.traffic_class, it's all just code that reads and checks for 
> those, so it's basically useless and dead code. This removal here allows 
> us to drop the atm.h patch.

I checked the git history, it looks like since 2007 only Lantiq's legacy 
driver (now ltq-atm) and various compat patches (now 
MIPS-lantiq-add-atm-hack.patch) are referencing 
ATM_VBR_NRT/ATM_VBR_RT/ATM_UBR_PLUS/ATM_GFR.

We have two options now. (a) Keep the Lantiq's hack in the tree for both 
platform and keep the include path amend in linux-atm. (b) proceed with 
this patch and probably backport it to v23 and v24. And with a follow up 
patch remove the corresponding ATM hacks from Lantiq and eventually from 
linux-atm.

> If that's the case too for lantiq, we could apply the same logic there 
> and make linux-atm shared again?

Yep. I like the plan 'b' for cleaning the tree from vendor's hacks, stop 
spreading them to other targets and simplifying maintenance.

> In any case, this set still works on my ipq40xx device and vdsl seems to 
> work just fine!

Have you gave a change to this series, Andre?

--
Sergey