[PATCH v2 0/2] MIPS: Fix missing proto and passing arg warnings

[PATCH v2 0/2] MIPS: Fix missing proto and passing arg warnings

[Serge Semin]

After getting my local tree rebased onto the kernel 6.8-rc3 the MIPS32
kernel build procedure produced a couple of warnings which I suggest to
fix in the framework of this series.

A first warning is of the "no previous prototype for `<func>`" type. In
particular my arch-specific code has the mips_cm_l2sync_phys_base() method
re-defined, but even though the function is global it' prototype isn't
declared anywhere. Fix that by moving the __mips_cm_l2sync_phys_base()
body to a weak implementation of mips_cm_l2sync_phys_base() and adding the
method prototype declaration to the mips/include/asm/mips-cm.h header
file. For the sake of unification a similar solution was provided for the
mips_cm_phys_base()/__mips_cm_phys_base() couple.

The following text describes the patches which have already merged in at
v1 stage of the patchset (see changelog v2).

One more case of the denoted earlier warning I spotted in the
self-extracting kernel (so called zboot) with the debug printouts enabled.
In particular there are several putc() method re-definitions available in:
arch/mips/boot/compressed/uart-prom.c
arch/mips/boot/compressed/uart-16550.c
arch/mips/boot/compressed/uart-alchemy.c
All of these files lacked the prototype declaration what caused having the
"no previous prototype for ‘putc’" printed on my build with the next
configs enabled:
CONFIG_SYS_SUPPORTS_ZBOOT=y
CONFIG_SYS_SUPPORTS_ZBOOT_UART_PROM=y
CONFIG_ZBOOT_LOAD_ADDRESS=0x85100000
CONFIG_DEBUG_ZBOOT=y

The second warning is of the "passing argument <x> of ‘<func>’ from
incompatible pointer type" type which I discovered in the
drivers/tty/mips_ejtag_fdc.c driver. The problem most likely happened due
to the commit ce7cbd9a6c81 ("tty: mips_ejtag_fdc: use u8 for character
pointers").

That's it for today.) Thanks for review in advance. Any tests are very
welcome.

Link: https://lore.kernel.org/linux-mips/20240215171740.14550-1-fancer.lancer@gmail.com
Changelog v2:
- Drop aleady applied pateches:
  [PATCH 3/4] mips: zboot: Fix "no previous prototype" build warning
  [PATCH 4/4] tty: mips_ejtag_fdc: Fix passing incompatible pointer type warning
- Drop Linux serial mailing list and the respective maintainers from the
  Cc-list.
- Covert the underscored versions of the CM2/L2-sync base address
  getters to being the body of the weakly defined original methods.

Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Serge Semin (2):
  mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function
  mips: cm: Convert __mips_cm_phys_base() to weak function

 arch/mips/include/asm/mips-cm.h | 20 ++++++++++++++++----
 arch/mips/kernel/mips-cm.c      | 10 ++--------
 2 files changed, 18 insertions(+), 12 deletions(-)

-- 
2.43.0

[PATCH v2 1/2] mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function

[Serge Semin]

The __mips_cm_l2sync_phys_base() and mips_cm_l2sync_phys_base() couple was
introduced in commit 9f98f3dd0c51 ("MIPS: Add generic CM probe & access
code") where the former method was a weak implementation of the later
function. Such design pattern permitted to re-define the original method
and to use the weak implementation in the new function. A similar approach
was introduced in the framework of another arch-specific programmable
interface: mips_cm_phys_base() and __mips_cm_phys_base(). The only
difference is that the underscored method of the later couple was declared
in the "asm/mips-cm.h" header file, but it wasn't done for the CM L2-sync
methods in the subject. Due to the missing global function declaration
the "missing prototype" warning was spotted in the framework of the commit
9a2036724cd6 ("mips: mark local function static if possible") and fixed
just be re-qualifying the weak method as static. Doing that broke what was
originally implied by having the weak implementation globally defined.

Let's fix the broken CM2 L2-sync arch-interface by dropping the static
qualifier and, seeing the implemented pattern hasn't been used for over 10
years but will be required soon (see the link for the discussion around
it), converting it to a single weakly defined method:
mips_cm_l2sync_phys_base().

Fixes: 9a2036724cd6 ("mips: mark local function static if possible")
Link: https://lore.kernel.org/linux-mips/20240215171740.14550-3-fancer.lancer@gmail.com
Signed-off-by: Serge Semin <fancer.lancer@gmail.com>

---

Changelog v2:
- Convert the underscored method to a single weakly defined function.
---
 arch/mips/include/asm/mips-cm.h | 13 +++++++++++++
 arch/mips/kernel/mips-cm.c      |  5 +----
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/mips/include/asm/mips-cm.h b/arch/mips/include/asm/mips-cm.h
index 23c67c0871b1..6cc79296c8ef 100644
--- a/arch/mips/include/asm/mips-cm.h
+++ b/arch/mips/include/asm/mips-cm.h
@@ -33,6 +33,19 @@ extern void __iomem *mips_cm_l2sync_base;
  */
 extern phys_addr_t __mips_cm_phys_base(void);
 
+/**
+ * mips_cm_l2sync_phys_base - retrieve the physical base address of the CM
+ *                            L2-sync region
+ *
+ * This function returns the physical base address of the Coherence Manager
+ * L2-cache only region. It provides a default implementation which reads the
+ * CMGCRL2OnlySyncBase register where available or returns a 4K region just
+ * behind the CM GCR base address. It may be overridden by platforms which
+ * determine this address in a different way by defining a function with the
+ * same prototype.
+ */
+extern phys_addr_t mips_cm_l2sync_phys_base(void);
+
 /*
  * mips_cm_is64 - determine CM register width
  *
diff --git a/arch/mips/kernel/mips-cm.c b/arch/mips/kernel/mips-cm.c
index 84b3affb9de8..268ac0b811e3 100644
--- a/arch/mips/kernel/mips-cm.c
+++ b/arch/mips/kernel/mips-cm.c
@@ -201,7 +201,7 @@ phys_addr_t __mips_cm_phys_base(void)
 phys_addr_t mips_cm_phys_base(void)
 	__attribute__((weak, alias("__mips_cm_phys_base")));
 
-static phys_addr_t __mips_cm_l2sync_phys_base(void)
+phys_addr_t __weak mips_cm_l2sync_phys_base(void)
 {
 	u32 base_reg;
 
@@ -217,9 +217,6 @@ static phys_addr_t __mips_cm_l2sync_phys_base(void)
 	return mips_cm_phys_base() + MIPS_CM_GCR_SIZE;
 }
 
-phys_addr_t mips_cm_l2sync_phys_base(void)
-	__attribute__((weak, alias("__mips_cm_l2sync_phys_base")));
-
 static void mips_cm_probe_l2sync(void)
 {
 	unsigned major_rev;
-- 
2.43.0

[PATCH v2 2/2] mips: cm: Convert __mips_cm_phys_base() to weak function

[Serge Semin]

Based on the design pattern utilized in the CM GCR base address getter
implementation, the platform-specific code is capable to re-define the
getter and re-use the weakly defined initial version. But since the
pattern hasn't been used for over 10 years and another similar case (CM
L2-sync only base address getter) has just been fixed, let's unify the
interface and convert it to a more traditional single weakly defined
method: mips_cm_phys_base() (see the link below for the discussion around
this).

Link: https://lore.kernel.org/linux-mips/20240215171740.14550-3-fancer.lancer@gmail.com
Signed-off-by: Serge Semin <fancer.lancer@gmail.com>

---

Changelog v2:
- Convert the underscored method to a single weakly defined function.
---
 arch/mips/include/asm/mips-cm.h | 7 +++----
 arch/mips/kernel/mips-cm.c      | 5 +----
 2 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/mips/include/asm/mips-cm.h b/arch/mips/include/asm/mips-cm.h
index 6cc79296c8ef..c4e27970d88f 100644
--- a/arch/mips/include/asm/mips-cm.h
+++ b/arch/mips/include/asm/mips-cm.h
@@ -22,16 +22,15 @@ extern void __iomem *mips_gcr_base;
 extern void __iomem *mips_cm_l2sync_base;
 
 /**
- * __mips_cm_phys_base - retrieve the physical base address of the CM
+ * mips_cm_phys_base - retrieve the physical base address of the CM
  *
  * This function returns the physical base address of the Coherence Manager
  * global control block, or 0 if no Coherence Manager is present. It provides
  * a default implementation which reads the CMGCRBase register where available,
  * and may be overridden by platforms which determine this address in a
- * different way by defining a function with the same prototype except for the
- * name mips_cm_phys_base (without underscores).
+ * different way by defining a function with the same prototype.
  */
-extern phys_addr_t __mips_cm_phys_base(void);
+extern phys_addr_t mips_cm_phys_base(void);
 
 /**
  * mips_cm_l2sync_phys_base - retrieve the physical base address of the CM
diff --git a/arch/mips/kernel/mips-cm.c b/arch/mips/kernel/mips-cm.c
index 268ac0b811e3..3a115fab5573 100644
--- a/arch/mips/kernel/mips-cm.c
+++ b/arch/mips/kernel/mips-cm.c
@@ -179,7 +179,7 @@ static char *cm3_causes[32] = {
 static DEFINE_PER_CPU_ALIGNED(spinlock_t, cm_core_lock);
 static DEFINE_PER_CPU_ALIGNED(unsigned long, cm_core_lock_flags);
 
-phys_addr_t __mips_cm_phys_base(void)
+phys_addr_t __weak mips_cm_phys_base(void)
 {
 	unsigned long cmgcr;
 
@@ -198,9 +198,6 @@ phys_addr_t __mips_cm_phys_base(void)
 	return (cmgcr & MIPS_CMGCRF_BASE) << (36 - 32);
 }
 
-phys_addr_t mips_cm_phys_base(void)
-	__attribute__((weak, alias("__mips_cm_phys_base")));
-
 phys_addr_t __weak mips_cm_l2sync_phys_base(void)
 {
 	u32 base_reg;
-- 
2.43.0

Re: [PATCH v2 1/2] mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function

[Arnd Bergmann]

On Mon, Feb 26, 2024, at 11:54, Serge Semin wrote:
> The __mips_cm_l2sync_phys_base() and mips_cm_l2sync_phys_base() couple was
> introduced in commit 9f98f3dd0c51 ("MIPS: Add generic CM probe & access
> code") where the former method was a weak implementation of the later
> function. Such design pattern permitted to re-define the original method
> and to use the weak implementation in the new function. A similar approach
> was introduced in the framework of another arch-specific programmable
> interface: mips_cm_phys_base() and __mips_cm_phys_base(). The only
> difference is that the underscored method of the later couple was declared
> in the "asm/mips-cm.h" header file, but it wasn't done for the CM L2-sync
> methods in the subject. Due to the missing global function declaration
> the "missing prototype" warning was spotted in the framework of the commit
> 9a2036724cd6 ("mips: mark local function static if possible") and fixed
> just be re-qualifying the weak method as static. Doing that broke what was
> originally implied by having the weak implementation globally defined.
>
> Let's fix the broken CM2 L2-sync arch-interface by dropping the static
> qualifier and, seeing the implemented pattern hasn't been used for over 10
> years but will be required soon (see the link for the discussion around
> it), converting it to a single weakly defined method:
> mips_cm_l2sync_phys_base().
>
> Fixes: 9a2036724cd6 ("mips: mark local function static if possible")
> Link: 
> https://lore.kernel.org/linux-mips/20240215171740.14550-3-fancer.lancer@gmail.com
> Signed-off-by: Serge Semin <fancer.lancer@gmail.com>

I'm sorry I introduced the regression here, thanks for addressing it.

> -static phys_addr_t __mips_cm_l2sync_phys_base(void)
> +phys_addr_t __weak mips_cm_l2sync_phys_base(void)
>  {
>  	u32 base_reg;
> 
> @@ -217,9 +217,6 @@ static phys_addr_t __mips_cm_l2sync_phys_base(void)
>  	return mips_cm_phys_base() + MIPS_CM_GCR_SIZE;
>  }
> 
> -phys_addr_t mips_cm_l2sync_phys_base(void)
> -	__attribute__((weak, alias("__mips_cm_l2sync_phys_base")));
> -

I generally have a bad feeling about weak functions, as they tend
to cause more problems than they solve, specifically with how they
hide what's going on, and how I still can't figure out what this
one aliases to.

Since the resolution of the alias is all done at link time
anyway, could you just convert these to an #ifdef check
that documents exactly when each of the versions is used?

      Arnd

Re: [PATCH v2 1/2] mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function

[Serge Semin]

Hi Arnd

On Mon, Feb 26, 2024 at 12:04:06PM +0100, Arnd Bergmann wrote:
> On Mon, Feb 26, 2024, at 11:54, Serge Semin wrote:
> > The __mips_cm_l2sync_phys_base() and mips_cm_l2sync_phys_base() couple was
> > introduced in commit 9f98f3dd0c51 ("MIPS: Add generic CM probe & access
> > code") where the former method was a weak implementation of the later
> > function. Such design pattern permitted to re-define the original method
> > and to use the weak implementation in the new function. A similar approach
> > was introduced in the framework of another arch-specific programmable
> > interface: mips_cm_phys_base() and __mips_cm_phys_base(). The only
> > difference is that the underscored method of the later couple was declared
> > in the "asm/mips-cm.h" header file, but it wasn't done for the CM L2-sync
> > methods in the subject. Due to the missing global function declaration
> > the "missing prototype" warning was spotted in the framework of the commit
> > 9a2036724cd6 ("mips: mark local function static if possible") and fixed
> > just be re-qualifying the weak method as static. Doing that broke what was
> > originally implied by having the weak implementation globally defined.
> >
> > Let's fix the broken CM2 L2-sync arch-interface by dropping the static
> > qualifier and, seeing the implemented pattern hasn't been used for over 10
> > years but will be required soon (see the link for the discussion around
> > it), converting it to a single weakly defined method:
> > mips_cm_l2sync_phys_base().
> >
> > Fixes: 9a2036724cd6 ("mips: mark local function static if possible")
> > Link: 
> > https://lore.kernel.org/linux-mips/20240215171740.14550-3-fancer.lancer@gmail.com
> > Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
> 
> I'm sorry I introduced the regression here, thanks for addressing it.

No worries. I've noticed it in my local tree only. Neither CM nor CM
L2-sync base address getters aren't currently re-defined in the
mainline code. So the generic kernel code hasn't been affected.

> 
> > -static phys_addr_t __mips_cm_l2sync_phys_base(void)
> > +phys_addr_t __weak mips_cm_l2sync_phys_base(void)
> >  {
> >  	u32 base_reg;
> > 
> > @@ -217,9 +217,6 @@ static phys_addr_t __mips_cm_l2sync_phys_base(void)
> >  	return mips_cm_phys_base() + MIPS_CM_GCR_SIZE;
> >  }
> > 
> > -phys_addr_t mips_cm_l2sync_phys_base(void)
> > -	__attribute__((weak, alias("__mips_cm_l2sync_phys_base")));
> > -
> 
> I generally have a bad feeling about weak functions, as they tend
> to cause more problems than they solve, specifically with how they
> hide what's going on, and how I still can't figure out what this
> one aliases to.
> 
> Since the resolution of the alias is all done at link time
> anyway, could you just convert these to an #ifdef check
> that documents exactly when each of the versions is used?

Not sure I've completely understood what you meant. Do you suggest to
add a mips_cm_l2sync_phys_base macro which would be defined if a
"strong" version of the method is defined (and surround the
underscored function by it)?

Please note after this patch is applied no aliases will
be left, but only a single weakly defined method:
mips_cm_l2sync_phys_base()
This is what we agreed to do with Thomas:
https://lore.kernel.org/linux-mips/pf6cvzper4g5364nqhd4wd2pmlkyygoymobeqduulpslcjhyy6@kf66z7chjbl3
Thus there will be no need in the macro you suggest since the
weak-version of the method will be discarded by the linker as it will
have been replaced with the "strong" one. 

-Serge(y)

> 
>       Arnd

Re: [PATCH v2 1/2] mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function

[Arnd Bergmann]

On Mon, Feb 26, 2024, at 12:27, Serge Semin wrote:
> On Mon, Feb 26, 2024 at 12:04:06PM +0100, Arnd Bergmann wrote:
>> On Mon, Feb 26, 2024, at 11:54, Serge Semin wrote:
s to.
>> 
>> Since the resolution of the alias is all done at link time
>> anyway, could you just convert these to an #ifdef check
>> that documents exactly when each of the versions is used?
>
> Not sure I've completely understood what you meant. Do you suggest to
> add a mips_cm_l2sync_phys_base macro which would be defined if a
> "strong" version of the method is defined (and surround the
> underscored function by it)?
>
> Please note after this patch is applied no aliases will
> be left, but only a single weakly defined method:
> mips_cm_l2sync_phys_base()
> This is what we agreed to do with Thomas:
> https://lore.kernel.org/linux-mips/pf6cvzper4g5364nqhd4wd2pmlkyygoymobeqduulpslcjhyy6@kf66z7chjbl3
> Thus there will be no need in the macro you suggest since the
> weak-version of the method will be discarded by the linker as it will
> have been replaced with the "strong" one. 

I meant that instead of having both a weak and an optional strong
version that get linked together, always define exactly one of the
two, such as:

#ifndef CONFIG_MIPS_CM_xxx
static phys_addr_t mips_cm_l2sync_phys_base(void)
{
       /* current implementation ... */
}
#endif

where CONFIG_MIPS_CM_xxx is the Kconfig symbol that decides
whether the file with the strong version is built or not.

This way you always get exactly one of the two versions
of the function built, the local version can be inlined
if the compiler thinks that is better, and the #ifdef
documents exactly whether the function is used or not
for a given configuration, rather than a reader having
to track down how many other definitions exist and whether
a config includes them.

       Arnd

Re: [PATCH v2 1/2] mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function

[Serge Semin]

On Mon, Feb 26, 2024 at 01:04:33PM +0100, Arnd Bergmann wrote:
> On Mon, Feb 26, 2024, at 12:27, Serge Semin wrote:
> > On Mon, Feb 26, 2024 at 12:04:06PM +0100, Arnd Bergmann wrote:
> >> On Mon, Feb 26, 2024, at 11:54, Serge Semin wrote:
> s to.
> >> 
> >> Since the resolution of the alias is all done at link time
> >> anyway, could you just convert these to an #ifdef check
> >> that documents exactly when each of the versions is used?
> >
> > Not sure I've completely understood what you meant. Do you suggest to
> > add a mips_cm_l2sync_phys_base macro which would be defined if a
> > "strong" version of the method is defined (and surround the
> > underscored function by it)?
> >
> > Please note after this patch is applied no aliases will
> > be left, but only a single weakly defined method:
> > mips_cm_l2sync_phys_base()
> > This is what we agreed to do with Thomas:
> > https://lore.kernel.org/linux-mips/pf6cvzper4g5364nqhd4wd2pmlkyygoymobeqduulpslcjhyy6@kf66z7chjbl3
> > Thus there will be no need in the macro you suggest since the
> > weak-version of the method will be discarded by the linker as it will
> > have been replaced with the "strong" one. 
> 
> I meant that instead of having both a weak and an optional strong
> version that get linked together, always define exactly one of the
> two, such as:
> 
> #ifndef CONFIG_MIPS_CM_xxx
> static phys_addr_t mips_cm_l2sync_phys_base(void)
> {
>        /* current implementation ... */
> }
> #endif
> 
> where CONFIG_MIPS_CM_xxx is the Kconfig symbol that decides
> whether the file with the strong version is built or not.
> 
> This way you always get exactly one of the two versions
> of the function built, the local version can be inlined
> if the compiler thinks that is better, and the #ifdef
> documents exactly whether the function is used or not
> for a given configuration, rather than a reader having
> to track down how many other definitions exist and whether
> a config includes them.

I see your point now. Thanks for clarification. IMO it would be less
readable due to the ifdef-ery and the new config, and less
maintainable due to the conditional compilation, but would provide a
more performant solution since the compiler will be able to inline the
singly used static method. Basically you suggest to emulate the weak
implementation by an additional kernel config. Not sure whether it
would be better than a well-known weak-attribute-based pattern. Anyway
let's wait for the Thomas' opinion about your suggestion. If he thinks
it would be better I'll update the patches.

-Serge(y)

> 
>        Arnd

Re: [PATCH v2 1/2] mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function

[Arnd Bergmann]

On Mon, Feb 26, 2024, at 13:20, Serge Semin wrote:
> On Mon, Feb 26, 2024 at 01:04:33PM +0100, Arnd Bergmann wrote:
>> On Mon, Feb 26, 2024, at 12:27, Serge Semin wrote:

> I see your point now. Thanks for clarification. IMO it would be less
> readable due to the ifdef-ery and the new config, and less
> maintainable due to the conditional compilation, but would provide a
> more performant solution since the compiler will be able to inline the
> singly used static method. Basically you suggest to emulate the weak
> implementation by an additional kernel config.

I mean the kernel config that you already need here, since
the strong version of the function is already optional.

> Not sure whether it would be better than a well-known
> weak-attribute-based pattern. Anyway let's wait for the
> Thomas' opinion about your suggestion. If he thinks
> it would be better I'll update the patches.

Weak functions are not used all that much outside of a
couple of parts of the kernel. There is a lot of them
in drivers/pci/, a little bit in acpi and efi, and
then a bit in arch/*/, though most of that is in mips.

Ifdef checks in .c files are not great, but at least they
are much more common than __weak functions and self-documenting.

     Arnd

Re: [PATCH v2 1/2] mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function

[Serge Semin]

On Mon, Feb 26, 2024 at 01:29:54PM +0100, Arnd Bergmann wrote:
> On Mon, Feb 26, 2024, at 13:20, Serge Semin wrote:
> > On Mon, Feb 26, 2024 at 01:04:33PM +0100, Arnd Bergmann wrote:
> >> On Mon, Feb 26, 2024, at 12:27, Serge Semin wrote:
> 
> > I see your point now. Thanks for clarification. IMO it would be less
> > readable due to the ifdef-ery and the new config, and less
> > maintainable due to the conditional compilation, but would provide a
> > more performant solution since the compiler will be able to inline the
> > singly used static method. Basically you suggest to emulate the weak
> > implementation by an additional kernel config.
> 
> I mean the kernel config that you already need here, since
> the strong version of the function is already optional.

Why would I need it if after this patch is applied the
mips_cm_l2sync_phys_base() method will be converted to a global weak
implementation?

> 
> > Not sure whether it would be better than a well-known
> > weak-attribute-based pattern. Anyway let's wait for the
> > Thomas' opinion about your suggestion. If he thinks
> > it would be better I'll update the patches.
> 
> Weak functions are not used all that much outside of a
> couple of parts of the kernel. There is a lot of them
> in drivers/pci/, a little bit in acpi and efi, and
> then a bit in arch/*/, though most of that is in mips.

+ a lot of them in kernel/*, some in mm/* .)

> 
> Ifdef checks in .c files are not great, but at least they
> are much more common than __weak functions and self-documenting.

Ok. I don't have concretely strong opinion about what is better. Let's
wait for what Thomas thinks about this.

-Serge(y)

> 
>      Arnd

Re: [PATCH v2 0/2] MIPS: Fix missing proto and passing arg warnings

[Thomas Bogendoerfer]

On Mon, Feb 26, 2024 at 01:54:20PM +0300, Serge Semin wrote:
> After getting my local tree rebased onto the kernel 6.8-rc3 the MIPS32
> kernel build procedure produced a couple of warnings which I suggest to
> fix in the framework of this series.
> 
> A first warning is of the "no previous prototype for `<func>`" type. In
> particular my arch-specific code has the mips_cm_l2sync_phys_base() method
> re-defined, but even though the function is global it' prototype isn't
> declared anywhere. Fix that by moving the __mips_cm_l2sync_phys_base()
> body to a weak implementation of mips_cm_l2sync_phys_base() and adding the
> method prototype declaration to the mips/include/asm/mips-cm.h header
> file. For the sake of unification a similar solution was provided for the
> mips_cm_phys_base()/__mips_cm_phys_base() couple.
> 
> The following text describes the patches which have already merged in at
> v1 stage of the patchset (see changelog v2).
> 
> One more case of the denoted earlier warning I spotted in the
> self-extracting kernel (so called zboot) with the debug printouts enabled.
> In particular there are several putc() method re-definitions available in:
> arch/mips/boot/compressed/uart-prom.c
> arch/mips/boot/compressed/uart-16550.c
> arch/mips/boot/compressed/uart-alchemy.c
> All of these files lacked the prototype declaration what caused having the
> "no previous prototype for ‘putc’" printed on my build with the next
> configs enabled:
> CONFIG_SYS_SUPPORTS_ZBOOT=y
> CONFIG_SYS_SUPPORTS_ZBOOT_UART_PROM=y
> CONFIG_ZBOOT_LOAD_ADDRESS=0x85100000
> CONFIG_DEBUG_ZBOOT=y
> 
> The second warning is of the "passing argument <x> of ‘<func>’ from
> incompatible pointer type" type which I discovered in the
> drivers/tty/mips_ejtag_fdc.c driver. The problem most likely happened due
> to the commit ce7cbd9a6c81 ("tty: mips_ejtag_fdc: use u8 for character
> pointers").
> 
> That's it for today.) Thanks for review in advance. Any tests are very
> welcome.
> 
> Link: https://lore.kernel.org/linux-mips/20240215171740.14550-1-fancer.lancer@gmail.com
> Changelog v2:
> - Drop aleady applied pateches:
>   [PATCH 3/4] mips: zboot: Fix "no previous prototype" build warning
>   [PATCH 4/4] tty: mips_ejtag_fdc: Fix passing incompatible pointer type warning
> - Drop Linux serial mailing list and the respective maintainers from the
>   Cc-list.
> - Covert the underscored versions of the CM2/L2-sync base address
>   getters to being the body of the weakly defined original methods.
> 
> Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: linux-mips@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> 
> Serge Semin (2):
>   mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function
>   mips: cm: Convert __mips_cm_phys_base() to weak function
> 
>  arch/mips/include/asm/mips-cm.h | 20 ++++++++++++++++----
>  arch/mips/kernel/mips-cm.c      | 10 ++--------
>  2 files changed, 18 insertions(+), 12 deletions(-)
> 
> -- 
> 2.43.0

series applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH v2 1/2] mips: cm: Convert __mips_cm_l2sync_phys_base() to weak function

[Thomas Bogendoerfer]

On Mon, Feb 26, 2024 at 04:11:05PM +0300, Serge Semin wrote:
> On Mon, Feb 26, 2024 at 01:29:54PM +0100, Arnd Bergmann wrote:
> > On Mon, Feb 26, 2024, at 13:20, Serge Semin wrote:
> > > On Mon, Feb 26, 2024 at 01:04:33PM +0100, Arnd Bergmann wrote:
> > >> On Mon, Feb 26, 2024, at 12:27, Serge Semin wrote:
> > 
> > > I see your point now. Thanks for clarification. IMO it would be less
> > > readable due to the ifdef-ery and the new config, and less
> > > maintainable due to the conditional compilation, but would provide a
> > > more performant solution since the compiler will be able to inline the
> > > singly used static method. Basically you suggest to emulate the weak
> > > implementation by an additional kernel config.
> > 
> > I mean the kernel config that you already need here, since
> > the strong version of the function is already optional.
> 
> Why would I need it if after this patch is applied the
> mips_cm_l2sync_phys_base() method will be converted to a global weak
> implementation?
> 
> > 
> > > Not sure whether it would be better than a well-known
> > > weak-attribute-based pattern. Anyway let's wait for the
> > > Thomas' opinion about your suggestion. If he thinks
> > > it would be better I'll update the patches.
> > 
> > Weak functions are not used all that much outside of a
> > couple of parts of the kernel. There is a lot of them
> > in drivers/pci/, a little bit in acpi and efi, and
> > then a bit in arch/*/, though most of that is in mips.
> 
> + a lot of them in kernel/*, some in mm/* .)
> 
> > 
> > Ifdef checks in .c files are not great, but at least they
> > are much more common than __weak functions and self-documenting.
> 
> Ok. I don't have concretely strong opinion about what is better. Let's
> wait for what Thomas thinks about this.

I've taken your patches as we get rid of this alias thing. As long as
there is no big push against __weak I'm ok with this case.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]