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

[Jeffrey Hugo]

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@xxxxxxxxxxxxxxxx>
> > > > > > 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@xxxxxxxxxxxxxxxx>
> > > > >
> > > > > 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