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Message-ID: <3879d287-81e0-5e25-8c58-f9554ce2303b@quicinc.com>
Date:   Tue, 11 Apr 2023 09:29:27 -0600
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Subject: Re: linux-next: build failure after merge of the driver-core tree
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From:   Jeffrey Hugo <quic_jhugo@quicinc.com>
To:     Greg KH <greg@kroah.com>
CC:     Oded Gabbay <ogabbay@kernel.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Dave Airlie <airlied@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        DRI <dri-devel@lists.freedesktop.org>,
        Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@quicinc.com>,
        "Linux Next Mailing List" <linux-next@vger.kernel.org>,
        Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
References: <20230411143812.11a4b00d@canb.auug.org.au>
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On 4/11/2023 9:26 AM, Jeffrey Hugo wrote:
> 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.

Also, I forgot to mention.  QAIC is sharing userspace components with 
WWAN, so we really cannot diverge from what WWAN has done and define a 
new API through the Accel node.

> 
> 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