Re: linux-next: build failure after merge of the driver-core tree
From: Jeffrey Hugo
Date: Tue Apr 11 2023 - 14:37:51 EST
On 4/11/2023 12:21 PM, Daniel Vetter wrote:
On Tue, Apr 11, 2023 at 11:18:29AM -0600, Jeffrey Hugo wrote:
On 4/11/2023 10:31 AM, Daniel Vetter wrote:
On Tue, Apr 11, 2023 at 09:29:27AM -0600, Jeffrey Hugo wrote:
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@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.
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.
So there is an accel/drm_device in the qaic driver, but there's also this
different class thing, which I don't get.
And yeah if that's an entirely orthogonal thing then I guess that should
be in a different driver/subsystem, all supported with the aux bus to
multiplex the underlying device.
I haven't found any explanation for what MHI is (or any of the other
acrynoms), so I'm entirely lost.
MHI is documented at Documentation/mhi/
It is also referenced in the QAIC documentation - Documentation/accel/qaic/
It stands for "Modem Host Interface" (arguably a bad name now, but you can
guess where it came from). It is a Qualcomm hardware block and associated
software protocol that provides logical channels over a hardware link. Most
commonly used for PCIe.
Pretty much any modern Qualcomm PCIe device implements it. 4G modems, 5G
modems, Wifi adapters, AIC100, etc. Instead of talking "PCIe", the host
talks "MHI" to the devices in most cases.
The core implementation for MHI exists in drivers/bus/mhi
MHI_UCI is the MHI Userspace Character Interface. It looked like most buses
(eg USB) provide some direct device access to userspace. MHI_UCI was
formulated along those same lines - provide direct userspace access to a
whitelist of channels. Qualcomm provides some fairly extensive userspace
utilities, and various communities have developed open source alternatives
using this mechanism.
MHI_UCI was proposed to the community as the common driver (misc device) for
all of the MHI devices. The Net folks came along, saw that it was used for
4G/5G modems (Wireless Wide Area Network devices or WWAN) and decided that
they would not tolerate a common implementation. They NACK'd MHI_UCI and
required that a WWAN specific subsystem be developed which would only
service WWAN devices. The Net folks decreed that other subsystems which
needed the same functionality need to have their own copy of the
implementation.
QAIC devices expose Sahara (a boot time protocol) which has an existing
userspace that is also used with Modems, although it looks like WWAN doesn't
currently support those generations of products today. QAIC devices also
support DIAG, which is currently supported in WWAN. The intent was to add
the QAIC support for DIAG at a later time since it is not required for the
bare minimum viable driver.
So, QAIC devices support the same services, would use the same userspace,
but can't use a common implementation because Jakub(net) doesn't want to
share and convinced Greg to go along. I'm not interested in pushing a cross
tree fight (arguably already did that with MHI_UCI). If neither Greg nor
Net will accept a common implementation that accelerators can use (QAIC),
then the only place I can fit this is in the Accel area.
Using aux bus seems to make little difference if QAIC is the only consumer
of this. I'm willing to refactor the implementation with some feedback and
guidence, but the uAPI seems set in stone due to the existing userspace and
WWAN (char devs with open/close/read/write/poll).
Ok, so MHI _is_ the bus. Thanks for the explainer, I should have searched
a bit more in Documentation/
What would make you less unhappy?
The MHI generic userspace driver interface needs to be in drivers/bus/mhi,
not in a random driver. I think we should revert 566fc96198b4
("accel/qaic: Add mhi_qaic_cntl") and re-land that through Greg's tree (or
wherever mhi patches go to). This of course assuming that the accel
userspace on top of the accel/drm_device does work stand-alone, and it's
just the tooling and other userspace that needs MHI_UCI. If we end with a
non-functional stack due to that, then I guess the entire driver is a bit
up for questions, because at least the accel runtime is supposed to just
run on top of the accel devnode and nothing else. Otherwise container
stuff gets really bad, among a lot of other things.
Looping in the MHI maintainer for your proposal.
The accel userspace can work without MHI_UCI.
The revert will be non-trivial so I'll look at posting that tomorrow.
-Jeff