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Date:   Wed, 20 Sep 2023 10:42:18 +0200
Message-ID: <87o7hxutg5.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Richard Fitzgerald <rf@opensource.cirrus.com>
Cc:     Nick Desaulniers <ndesaulniers@google.com>, <tiwai@suse.com>,
        <alsa-devel@alsa-project.org>, <patches@opensource.cirrus.com>,
        <linux-kernel@vger.kernel.org>, <llvm@lists.linux.dev>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Daniel Scally <djrscally@gmail.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        <linux-acpi@vger.kernel.org>
Subject: Re: [PATCH 2/2] ALSA: hda: cirrus_scodec: Add KUnit test
In-Reply-To: <9e2291c1-9a6c-ba6b-ea0f-ad130d2596f4@opensource.cirrus.com>
References: <20230918095129.440-1-rf@opensource.cirrus.com>
        <20230918095129.440-3-rf@opensource.cirrus.com>
        <ZQoILN6QCjzosCOs@google.com>
        <874jjpwd4i.wl-tiwai@suse.de>
        <9e2291c1-9a6c-ba6b-ea0f-ad130d2596f4@opensource.cirrus.com>
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On Wed, 20 Sep 2023 10:27:58 +0200,
Richard Fitzgerald wrote:
> 
> On 20/9/23 07:51, Takashi Iwai wrote:
> > On Tue, 19 Sep 2023 22:44:28 +0200,
> > Nick Desaulniers wrote:
> >> 
> >> On Mon, Sep 18, 2023 at 10:51:29AM +0100, Richard Fitzgerald wrote:
> > (snip)
> >>> +static void cirrus_scodec_test_set_gpio_ref_arg(struct software_node_ref_args *arg,
> >>> +						int gpio_num)
> >>> +{
> >>> +	struct software_node_ref_args template =
> >>> +		SOFTWARE_NODE_REFERENCE(&cirrus_scodec_test_gpio_swnode, gpio_num, 0);
> >> 
> >> I'm observing the following error when building with:
> >> 
> >> $ make LLVM=1 -j128 allmodconfig sound/pci/hda/cirrus_scodec_test.o
> >> 
> >> sound/pci/hda/cirrus_scodec_test.c:151:60: error: initializer element is not a compile-time constant
> >>    151 |                 SOFTWARE_NODE_REFERENCE(&cirrus_scodec_test_gpio_swnode, gpio_num, 0);
> >>        |                                                                          ^~~~~~~~
> >> /builds/linux/include/linux/property.h:291:37: note: expanded from macro 'SOFTWARE_NODE_REFERENCE'
> >>    291 |         .nargs = ARRAY_SIZE(((u64[]){ 0, ##__VA_ARGS__ })) - 1, \
> >>        |                                            ^~~~~~~~~~~
> >> /builds/linux/include/linux/kernel.h:57:75: note: expanded from macro 'ARRAY_SIZE'
> >>     57 | #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
> >>        |                                                                           ^~~
> >> /builds/linux/include/linux/compiler.h:228:59: note: expanded from macro '__must_be_array'
> >>    228 | #define __must_be_array(a)      BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
> >>        |                                                                ^
> >> /builds/linux/include/linux/compiler_types.h:366:63: note: expanded from macro '__same_type'
> >>    366 | #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
> >>        |                                                               ^
> >> /builds/linux/include/linux/build_bug.h:16:62: note: expanded from macro 'BUILD_BUG_ON_ZERO'
> >>     16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
> >>        |                                                              ^
> > 
> > Hm, this looks like some inconsistent handling of the temporary array
> > passed to ARRAY_SIZE() in the SOFTWARE_NODE_REFERENCE macro.  LLVM
> > can't treat it if it contains a variable in the given array, while GCC
> > doesn't care.
> > 
> > A hackish workaround would be the patch like below, but it's really
> > ugly.  Ideally speaking, it should be fixed in linux/properties.h, but
> > I have no idea how to fix there for LLVM.
> > 
> > Adding more relevant people to Cc.
> > 
> > 
> > thanks,
> > 
> > Takashi
> > 
> > --- a/sound/pci/hda/cirrus_scodec_test.c
> > +++ b/sound/pci/hda/cirrus_scodec_test.c
> > @@ -148,8 +148,9 @@ static void cirrus_scodec_test_set_gpio_ref_arg(struct software_node_ref_args *a
> >   						int gpio_num)
> >   {
> >   	struct software_node_ref_args template =
> > -		SOFTWARE_NODE_REFERENCE(&cirrus_scodec_test_gpio_swnode, gpio_num, 0);
> > +		SOFTWARE_NODE_REFERENCE(&cirrus_scodec_test_gpio_swnode, 0, 0);
> >   +	template.args[0] = gpio_num;
> >   	*arg = template;
> >   }
> >   
> 
> The tests must generate sw nodes dynamically, not a fixed const struct.
> I wanted to avoid directly accessing the internals of the SW node
> structures. Use only the macros.
> 
> I can rewrite this code to open-code the construction of the
> software_node_ref_args. Or I can wait a while in case anyone has a
> suggested fix for the macros.
> 
> Its seems reasonable that you should be able to create software nodes
> dynamically. A "real" use of these might need to construct the data from
> some other data that is not known at runtime (for example, where the
> ACPI provides some information but not the necessary info).

Yeah, fixing the macro would be ideal.

An easy and compromise solution would be to factor out the
ARRAY_SIZE() call and allow giving nargs explicitly.

e.g.

--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -285,13 +285,18 @@ struct software_node_ref_args {
 	u64 args[NR_FWNODE_REFERENCE_ARGS];
 };
 
-#define SOFTWARE_NODE_REFERENCE(_ref_, ...)			\
+#define __SOFTWARE_NODE_REFERENCE(_ref_, _nargs_, ...)		\
 (const struct software_node_ref_args) {				\
 	.node = _ref_,						\
-	.nargs = ARRAY_SIZE(((u64[]){ 0, ##__VA_ARGS__ })) - 1,	\
+	.nargs = _nargs_,					\
 	.args = { __VA_ARGS__ },				\
 }
 
+#define SOFTWARE_NODE_REFERENCE(_ref_, ...) \
+	__SOFTWARE_NODE_REFERENCE(_ref_,\
+		ARRAY_SIZE(((u64[]){ 0, ##__VA_ARGS__ })) - 1,\
+		##__VA_ARGS__)
+
 /**
  * struct property_entry - "Built-in" device property representation.
  * @name: Name of the property.
--- a/sound/pci/hda/cirrus_scodec_test.c
+++ b/sound/pci/hda/cirrus_scodec_test.c
@@ -148,7 +148,7 @@ static void cirrus_scodec_test_set_gpio_ref_arg(struct software_node_ref_args *a
 						int gpio_num)
 {
 	struct software_node_ref_args template =
-		SOFTWARE_NODE_REFERENCE(&cirrus_scodec_test_gpio_swnode, gpio_num, 0);
+		__SOFTWARE_NODE_REFERENCE(&cirrus_scodec_test_gpio_swnode, 2, gpio_num, 0);
 
 	*arg = template;
 }


... though I'm not convinced by this change, either.


Takashi