Re: linux-next: build failure after merge of the driver-core tree

[Jeffrey Hugo <quic_jhugo@quicinc.com>]

On 4/11/2023 9:13 AM, Greg KH wrote:
> On Tue, Apr 11, 2023 at 09:08:39AM -0600, Jeffrey Hugo wrote:
>> On 4/11/2023 9:01 AM, Daniel Vetter wrote:
>>> On Tue, Apr 11, 2023 at 12:40:28PM +0200, Greg KH wrote:
>>>> On Tue, Apr 11, 2023 at 11:55:20AM +0200, Daniel Vetter wrote:
>>>>> On Tue, Apr 11, 2023 at 02:38:12PM +1000, Stephen Rothwell wrote:
>>>>>> Hi all,
>>>>>>
>>>>>> After merging the driver-core tree, today's linux-next build (x86_64
>>>>>> allmodconfig) failed like this:
>>>>>>
>>>>>> In file included from include/linux/linkage.h:7,
>>>>>>                    from include/linux/kernel.h:17,
>>>>>>                    from drivers/accel/qaic/mhi_qaic_ctrl.c:4:
>>>>>> drivers/accel/qaic/mhi_qaic_ctrl.c: In function 'mhi_qaic_ctrl_init':
>>>>>> include/linux/export.h:27:22: error: passing argument 1 of 'class_create' from incompatible pointer type [-Werror=incompatible-pointer-types]
>>>>>>      27 | #define THIS_MODULE (&__this_module)
>>>>>>         |                     ~^~~~~~~~~~~~~~~
>>>>>>         |                      |
>>>>>>         |                      struct module *
>>>>>> drivers/accel/qaic/mhi_qaic_ctrl.c:544:38: note: in expansion of macro 'THIS_MODULE'
>>>>>>     544 |         mqc_dev_class = class_create(THIS_MODULE, MHI_QAIC_CTRL_DRIVER_NAME);
>>>>>>         |                                      ^~~~~~~~~~~
>>>>>> In file included from include/linux/device.h:31,
>>>>>>                    from include/linux/mhi.h:9,
>>>>>>                    from drivers/accel/qaic/mhi_qaic_ctrl.c:5:
>>>>>> include/linux/device/class.h:229:54: note: expected 'const char *' but argument is of type 'struct module *'
>>>>>>     229 | struct class * __must_check class_create(const char *name);
>>>>>>         |                                          ~~~~~~~~~~~~^~~~
>>>>>> drivers/accel/qaic/mhi_qaic_ctrl.c:544:25: error: too many arguments to function 'class_create'
>>>>>>     544 |         mqc_dev_class = class_create(THIS_MODULE, MHI_QAIC_CTRL_DRIVER_NAME);
>>>>>>         |                         ^~~~~~~~~~~~
>>>>>> include/linux/device/class.h:229:29: note: declared here
>>>>>>     229 | struct class * __must_check class_create(const char *name);
>>>>>>         |                             ^~~~~~~~~~~~
>>>>>>
>>>>>> Caused by commit
>>>>>>
>>>>>>     1aaba11da9aa ("driver core: class: remove module * from class_create()")
>>>>>>
>>>>>> interacting with commit
>>>>>>
>>>>>>     566fc96198b4 ("accel/qaic: Add mhi_qaic_cntl")
>>>>>>
>>>>>> from the drm tree.
>>>>>>
>>>>>> I have applied the following merge fix patch for today.
>>>>>>
>>>>>> From: Stephen Rothwell <sfr@canb.auug.org.au>
>>>>>> Date: Tue, 11 Apr 2023 14:16:57 +1000
>>>>>> Subject: [PATCH] fixup for "driver core: class: remove module * from class_create()"
>>>>>>
>>>>>> interacting with "accel/qaic: Add mhi_qaic_cntl"
>>>>>>
>>>>>> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
>>>>>
>>>>> Thanks for the fixup. Since Dave is out I've made a note about this in my
>>>>> handover mail so it won't get lost in the drm-next merge window pull. I
>>>>> don't think we need any other coordination than mention it in each pull to
>>>>> Linus, topic tree seems overkill for this. Plus there's no way I can
>>>>> untangle the drm tree anyway :-).
>>>>
>>>> Want me to submit a patch for the drm tree that moves this to use
>>>> class_register() instead, which will make the merge/build issue go away
>>>> for you?  That's my long-term goal here anyway, so converting this new
>>>> code to this api today would be something I have to do eventually :)
>>>
>>> We kinda closed drm-next for feature work mostly already (just pulling
>>> stuff in from subtrees), so won't really help for this merge window.
>>>
>>> For everything else I think this is up to Oded, I had no idea qaic needed
>>> it's entire own dev class and I don't want to dig into this for the risk I
>>> might freak out :-)
>>>
>>> Adding Oded.
>>>
>>> Cheers, Daniel
>>
>> Sorry for the mess.
>>
>> I made a note to update to class_register() once my drm-misc access is
>> sorted out.  Looks like we'll address the conflict in the merge window, and
>> catch the update to the new API in the following release.
> 
> Wait, I think the large question is, "why does this need a separate
> class"?  Why are you not using the accel char device and class?  That is
> what everything under accel/ should be using, otherwise why put it in
> there?
> 
> And what exactly are you using that class for?  Just device nodes?  If
> so, how many?
> 
> thanks,
> 
> greg k-h


Remember MHI_UCI that then evolved into the WWAN subsystem?  I pointed 
out at the time that AIC100/QAIC would need the same functionality. 
You/Jakub told myself/Mani/Loic that a combined implementation is not 
acceptable, and every area needs to implement their own version of MHI_UCI.

We took the WWAN subsystem and simplified it to meet our needs.

The functionality is QAIC specific, so wedging it into the Accel node 
seems to be a poor fit as it would subject Habana and iVPU to the same.

We need (eventually) 128 device nodes.  We have systems with 32 QAIC 
devices, and each QAIC device uses 4 device nodes (32 * 4 = 128).  WWAN 
subsystem would be similar.  Looks like each 5G modem is 6 nodes per 
device, so if you had 22 5G modems on a system, you'd have 132 device 
nodes.  I'm not aware of any such system, but it could exist.

-Jeff