[PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[Petr Mladek]

The generic FourCC format always prints the data using the big endian
order. It is generic because it allows to read the data using a custom
ordering.

The current code uses "n" for reading data in the reverse host ordering.
It makes the 4 variants [hnbl] consistent with the generic printing
of IPv4 addresses.

Unfortunately, it creates confusion on big endian systems. For example,
it shows the data &(u32)0x67503030 as

	%p4cn	00Pg (0x30305067)

But people expect that the ordering stays the same. The network ordering
is a big-endian ordering.

The problem is that the semantic is not the same. The modifiers affect
the output ordering of IPv4 addresses while they affect the reading order
in case of FourCC code.

Avoid the confusion by replacing the "n" modifier with "hR", aka
reverse host ordering. It is inspired by the existing %p[mM]R printf
format.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Closes: https://lore.kernel.org/r/CAMuHMdV9tX=TG7E_CrSF=2PY206tXf+_yYRuacG48EWEtJLo-Q@mail.gmail.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
Hi,

I am sending this as a proper patch. It would be nice to queue it
together with the other patches adding the generic printf modifiers.

Best Regards,
Petr
---
Documentation/core-api/printk-formats.rst | 10 +++++-----
 lib/tests/printf_kunit.c                  |  4 ++--
 lib/vsprintf.c                            | 11 ++++++++---
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index 125fd0397510..f531873bb3c9 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -652,7 +652,7 @@ Generic FourCC code
 -------------------
 
 ::
-	%p4c[hnlb]	gP00 (0x67503030)
+	%p4c[h[R]lb]	gP00 (0x67503030)
 
 Print a generic FourCC code, as both ASCII characters and its numerical
 value as hexadecimal.
@@ -660,23 +660,23 @@ value as hexadecimal.
 The generic FourCC code is always printed in the big-endian format,
 the most significant byte first. This is the opposite of V4L/DRM FourCCs.
 
-The additional ``h``, ``n``, ``l``, and ``b`` specifiers define what
+The additional ``h``, ``hR``, ``l``, and ``b`` specifiers define what
 endianness is used to load the stored bytes. The data might be interpreted
-using the host byte order, network byte order, little-endian, or big-endian.
+using the host, reversed host byte order, little-endian, or big-endian.
 
 Passed by reference.
 
 Examples for a little-endian machine, given &(u32)0x67503030::
 
 	%p4ch	gP00 (0x67503030)
-	%p4cn	00Pg (0x30305067)
+	%p4chR	00Pg (0x30305067)
 	%p4cl	gP00 (0x67503030)
 	%p4cb	00Pg (0x30305067)
 
 Examples for a big-endian machine, given &(u32)0x67503030::
 
 	%p4ch	gP00 (0x67503030)
-	%p4cn	00Pg (0x30305067)
+	%p4chR	00Pg (0x30305067)
 	%p4cl	00Pg (0x30305067)
 	%p4cb	gP00 (0x67503030)
 
diff --git a/lib/tests/printf_kunit.c b/lib/tests/printf_kunit.c
index b1fa0dcea52f..bc54cca2d7a6 100644
--- a/lib/tests/printf_kunit.c
+++ b/lib/tests/printf_kunit.c
@@ -726,7 +726,7 @@ static void fourcc_pointer(struct kunit *kunittest)
 	static const struct fourcc_struct try_ch[] = {
 		{ 0x41424344, "ABCD (0x41424344)", },
 	};
-	static const struct fourcc_struct try_cn[] = {
+	static const struct fourcc_struct try_chR[] = {
 		{ 0x41424344, "DCBA (0x44434241)", },
 	};
 	static const struct fourcc_struct try_cl[] = {
@@ -738,7 +738,7 @@ static void fourcc_pointer(struct kunit *kunittest)
 
 	fourcc_pointer_test(kunittest, try_cc, ARRAY_SIZE(try_cc), "%p4cc");
 	fourcc_pointer_test(kunittest, try_ch, ARRAY_SIZE(try_ch), "%p4ch");
-	fourcc_pointer_test(kunittest, try_cn, ARRAY_SIZE(try_cn), "%p4cn");
+	fourcc_pointer_test(kunittest, try_chR, ARRAY_SIZE(try_chR), "%p4chR");
 	fourcc_pointer_test(kunittest, try_cl, ARRAY_SIZE(try_cl), "%p4cl");
 	fourcc_pointer_test(kunittest, try_cb, ARRAY_SIZE(try_cb), "%p4cb");
 }
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 2c5de4216415..34587b2dbdb1 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1804,9 +1804,8 @@ char *fourcc_string(char *buf, char *end, const u32 *fourcc,
 	orig = get_unaligned(fourcc);
 	switch (fmt[2]) {
 	case 'h':
-		break;
-	case 'n':
-		orig = swab32(orig);
+		if (fmt[3] == 'R')
+			orig = swab32(orig);
 		break;
 	case 'l':
 		orig = (__force u32)cpu_to_le32(orig);
@@ -2396,6 +2395,12 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
  *       read the documentation (path below) first.
  * - 'NF' For a netdev_features_t
  * - '4cc' V4L2 or DRM FourCC code, with endianness and raw numerical value.
+ * - '4c[h[R]lb]' For generic FourCC code with raw numerical value. Both are
+ *	 displayed in the big-endian format. This is the opposite of V4L2 or
+ *	 DRM FourCCs.
+ *	 The additional specifiers define what endianness is used to load
+ *	 the stored bytes. The data might be interpreted using the host,
+ *	 reversed host byte order, little-endian, or big-endian.
  * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with
  *            a certain separator (' ' by default):
  *              C colon
-- 
2.49.0

Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[Aditya Garg]

On 28-04-2025 06:01 pm, Petr Mladek wrote:
> The generic FourCC format always prints the data using the big endian
> order. It is generic because it allows to read the data using a custom
> ordering.
> 
> The current code uses "n" for reading data in the reverse host ordering.
> It makes the 4 variants [hnbl] consistent with the generic printing
> of IPv4 addresses.
> 
> Unfortunately, it creates confusion on big endian systems. For example,
> it shows the data &(u32)0x67503030 as
> 
> 	%p4cn	00Pg (0x30305067)
> 
> But people expect that the ordering stays the same. The network ordering
> is a big-endian ordering.
> 
> The problem is that the semantic is not the same. The modifiers affect
> the output ordering of IPv4 addresses while they affect the reading order
> in case of FourCC code.
> 
> Avoid the confusion by replacing the "n" modifier with "hR", aka
> reverse host ordering. It is inspired by the existing %p[mM]R printf
> format.
> 
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Closes: https://lore.kernel.org/r/CAMuHMdV9tX=TG7E_CrSF=2PY206tXf+_yYRuacG48EWEtJLo-Q@mail.gmail.com
> Signed-off-by: Petr Mladek <pmladek@suse.com>

Reviewed-by: Aditya Garg <gargaditya08@live.com>

> ---
> Hi,
> 
> I am sending this as a proper patch. It would be nice to queue it
> together with the other patches adding the generic printf modifiers.

Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[Geert Uytterhoeven]

On Mon, 28 Apr 2025 at 14:31, Petr Mladek <pmladek@suse.com> wrote:
> The generic FourCC format always prints the data using the big endian
> order. It is generic because it allows to read the data using a custom
> ordering.
>
> The current code uses "n" for reading data in the reverse host ordering.
> It makes the 4 variants [hnbl] consistent with the generic printing
> of IPv4 addresses.
>
> Unfortunately, it creates confusion on big endian systems. For example,
> it shows the data &(u32)0x67503030 as
>
>         %p4cn   00Pg (0x30305067)
>
> But people expect that the ordering stays the same. The network ordering
> is a big-endian ordering.
>
> The problem is that the semantic is not the same. The modifiers affect
> the output ordering of IPv4 addresses while they affect the reading order
> in case of FourCC code.
>
> Avoid the confusion by replacing the "n" modifier with "hR", aka
> reverse host ordering. It is inspired by the existing %p[mM]R printf
> format.
>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Closes: https://lore.kernel.org/r/CAMuHMdV9tX=TG7E_CrSF=2PY206tXf+_yYRuacG48EWEtJLo-Q@mail.gmail.com
> Signed-off-by: Petr Mladek <pmladek@suse.com>

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[Alyssa Rosenzweig]

Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>

Since the other patches went thru drm-misc-next, I guess this should
too?


Le Mon , Apr 28, 2025 at 02:31:32PM +0200, Petr Mladek a écrit :
> The generic FourCC format always prints the data using the big endian
> order. It is generic because it allows to read the data using a custom
> ordering.
> 
> The current code uses "n" for reading data in the reverse host ordering.
> It makes the 4 variants [hnbl] consistent with the generic printing
> of IPv4 addresses.
> 
> Unfortunately, it creates confusion on big endian systems. For example,
> it shows the data &(u32)0x67503030 as
> 
> 	%p4cn	00Pg (0x30305067)
> 
> But people expect that the ordering stays the same. The network ordering
> is a big-endian ordering.
> 
> The problem is that the semantic is not the same. The modifiers affect
> the output ordering of IPv4 addresses while they affect the reading order
> in case of FourCC code.
> 
> Avoid the confusion by replacing the "n" modifier with "hR", aka
> reverse host ordering. It is inspired by the existing %p[mM]R printf
> format.
> 
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Closes: https://lore.kernel.org/r/CAMuHMdV9tX=TG7E_CrSF=2PY206tXf+_yYRuacG48EWEtJLo-Q@mail.gmail.com
> Signed-off-by: Petr Mladek <pmladek@suse.com>
> ---
> Hi,
> 
> I am sending this as a proper patch. It would be nice to queue it
> together with the other patches adding the generic printf modifiers.
> 
> Best Regards,
> Petr
> ---
> Documentation/core-api/printk-formats.rst | 10 +++++-----
>  lib/tests/printf_kunit.c                  |  4 ++--
>  lib/vsprintf.c                            | 11 ++++++++---
>  3 files changed, 15 insertions(+), 10 deletions(-)
> 
> diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
> index 125fd0397510..f531873bb3c9 100644
> --- a/Documentation/core-api/printk-formats.rst
> +++ b/Documentation/core-api/printk-formats.rst
> @@ -652,7 +652,7 @@ Generic FourCC code
>  -------------------
>  
>  ::
> -	%p4c[hnlb]	gP00 (0x67503030)
> +	%p4c[h[R]lb]	gP00 (0x67503030)
>  
>  Print a generic FourCC code, as both ASCII characters and its numerical
>  value as hexadecimal.
> @@ -660,23 +660,23 @@ value as hexadecimal.
>  The generic FourCC code is always printed in the big-endian format,
>  the most significant byte first. This is the opposite of V4L/DRM FourCCs.
>  
> -The additional ``h``, ``n``, ``l``, and ``b`` specifiers define what
> +The additional ``h``, ``hR``, ``l``, and ``b`` specifiers define what
>  endianness is used to load the stored bytes. The data might be interpreted
> -using the host byte order, network byte order, little-endian, or big-endian.
> +using the host, reversed host byte order, little-endian, or big-endian.
>  
>  Passed by reference.
>  
>  Examples for a little-endian machine, given &(u32)0x67503030::
>  
>  	%p4ch	gP00 (0x67503030)
> -	%p4cn	00Pg (0x30305067)
> +	%p4chR	00Pg (0x30305067)
>  	%p4cl	gP00 (0x67503030)
>  	%p4cb	00Pg (0x30305067)
>  
>  Examples for a big-endian machine, given &(u32)0x67503030::
>  
>  	%p4ch	gP00 (0x67503030)
> -	%p4cn	00Pg (0x30305067)
> +	%p4chR	00Pg (0x30305067)
>  	%p4cl	00Pg (0x30305067)
>  	%p4cb	gP00 (0x67503030)
>  
> diff --git a/lib/tests/printf_kunit.c b/lib/tests/printf_kunit.c
> index b1fa0dcea52f..bc54cca2d7a6 100644
> --- a/lib/tests/printf_kunit.c
> +++ b/lib/tests/printf_kunit.c
> @@ -726,7 +726,7 @@ static void fourcc_pointer(struct kunit *kunittest)
>  	static const struct fourcc_struct try_ch[] = {
>  		{ 0x41424344, "ABCD (0x41424344)", },
>  	};
> -	static const struct fourcc_struct try_cn[] = {
> +	static const struct fourcc_struct try_chR[] = {
>  		{ 0x41424344, "DCBA (0x44434241)", },
>  	};
>  	static const struct fourcc_struct try_cl[] = {
> @@ -738,7 +738,7 @@ static void fourcc_pointer(struct kunit *kunittest)
>  
>  	fourcc_pointer_test(kunittest, try_cc, ARRAY_SIZE(try_cc), "%p4cc");
>  	fourcc_pointer_test(kunittest, try_ch, ARRAY_SIZE(try_ch), "%p4ch");
> -	fourcc_pointer_test(kunittest, try_cn, ARRAY_SIZE(try_cn), "%p4cn");
> +	fourcc_pointer_test(kunittest, try_chR, ARRAY_SIZE(try_chR), "%p4chR");
>  	fourcc_pointer_test(kunittest, try_cl, ARRAY_SIZE(try_cl), "%p4cl");
>  	fourcc_pointer_test(kunittest, try_cb, ARRAY_SIZE(try_cb), "%p4cb");
>  }
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 2c5de4216415..34587b2dbdb1 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1804,9 +1804,8 @@ char *fourcc_string(char *buf, char *end, const u32 *fourcc,
>  	orig = get_unaligned(fourcc);
>  	switch (fmt[2]) {
>  	case 'h':
> -		break;
> -	case 'n':
> -		orig = swab32(orig);
> +		if (fmt[3] == 'R')
> +			orig = swab32(orig);
>  		break;
>  	case 'l':
>  		orig = (__force u32)cpu_to_le32(orig);
> @@ -2396,6 +2395,12 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
>   *       read the documentation (path below) first.
>   * - 'NF' For a netdev_features_t
>   * - '4cc' V4L2 or DRM FourCC code, with endianness and raw numerical value.
> + * - '4c[h[R]lb]' For generic FourCC code with raw numerical value. Both are
> + *	 displayed in the big-endian format. This is the opposite of V4L2 or
> + *	 DRM FourCCs.
> + *	 The additional specifiers define what endianness is used to load
> + *	 the stored bytes. The data might be interpreted using the host,
> + *	 reversed host byte order, little-endian, or big-endian.
>   * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with
>   *            a certain separator (' ' by default):
>   *              C colon
> -- 
> 2.49.0
> 

Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[Aditya Garg]

On 28-04-2025 10:30 pm, Alyssa Rosenzweig wrote:
> Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
> 
> Since the other patches went thru drm-misc-next, I guess this should
> too?

I think yes.
> 
> 
> Le Mon , Apr 28, 2025 at 02:31:32PM +0200, Petr Mladek a écrit :
>> The generic FourCC format always prints the data using the big endian
>> order. It is generic because it allows to read the data using a custom
>> ordering.
>>
>> The current code uses "n" for reading data in the reverse host ordering.
>> It makes the 4 variants [hnbl] consistent with the generic printing
>> of IPv4 addresses.
>>
>> Unfortunately, it creates confusion on big endian systems. For example,
>> it shows the data &(u32)0x67503030 as
>>
>> 	%p4cn	00Pg (0x30305067)
>>
>> But people expect that the ordering stays the same. The network ordering
>> is a big-endian ordering.
>>
>> The problem is that the semantic is not the same. The modifiers affect
>> the output ordering of IPv4 addresses while they affect the reading order
>> in case of FourCC code.
>>
>> Avoid the confusion by replacing the "n" modifier with "hR", aka
>> reverse host ordering. It is inspired by the existing %p[mM]R printf
>> format.
>>
>> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
>> Closes: https://lore.kernel.org/r/CAMuHMdV9tX=TG7E_CrSF=2PY206tXf+_yYRuacG48EWEtJLo-Q@mail.gmail.com
>> Signed-off-by: Petr Mladek <pmladek@suse.com>
>> ---
>> Hi,
>>
>> I am sending this as a proper patch. It would be nice to queue it
>> together with the other patches adding the generic printf modifiers.

Atleast thats what this says.

Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[Petr Mladek]

On Mon 2025-04-28 22:38:13, Aditya Garg wrote:
> 
> 
> On 28-04-2025 10:30 pm, Alyssa Rosenzweig wrote:
> > Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
> > 
> > Since the other patches went thru drm-misc-next, I guess this should
> > too?
> 
> I think yes.

Yes, it would be ideal to add this to drm-misc-next as well.

Best Regards,
Petr

Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[Alyssa Rosenzweig]

Le Tue, Apr 29, 2025 at 01:39:43PM +0200, Petr Mladek a écrit :
> On Mon 2025-04-28 22:38:13, Aditya Garg wrote:
> > 
> > 
> > On 28-04-2025 10:30 pm, Alyssa Rosenzweig wrote:
> > > Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
> > > 
> > > Since the other patches went thru drm-misc-next, I guess this should
> > > too?
> > 
> > I think yes.
> 
> Yes, it would be ideal to add this to drm-misc-next as well.

ok, will queue this

Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[Aditya Garg]

Hi Petr

> The generic FourCC format always prints the data using the big endian
> order. It is generic because it allows to read the data using a custom
> ordering.
> 
> The current code uses "n" for reading data in the reverse host ordering.
> It makes the 4 variants [hnbl] consistent with the generic printing
> of IPv4 addresses.
> 
> Unfortunately, it creates confusion on big endian systems. For example,
> it shows the data &(u32)0x67503030 as
> 
> 	%p4cn	00Pg (0x30305067)
> 
> But people expect that the ordering stays the same. The network ordering
> is a big-endian ordering.
> 
> The problem is that the semantic is not the same. The modifiers affect
> the output ordering of IPv4 addresses while they affect the reading order
> in case of FourCC code.
> 
> Avoid the confusion by replacing the "n" modifier with "hR", aka
> reverse host ordering. It is inspired by the existing %p[mM]R printf
> format.
> 
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Closes: https://lore.kernel.org/r/CAMuHMdV9tX=TG7E_CrSF=2PY206tXf+_yYRuacG48EWEtJLo-Q@mail.gmail.com
> Signed-off-by: Petr Mladek <pmladek@suse.com>
> ---

I just realised you forgot to fix checkpatch.pl with your update:

https://gitlab.freedesktop.org/drm/misc/kernel/-/blob/1938479b2720ebc05aab349c7dc0a53921ff7c87/scripts/checkpatch.pl#L6894

Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

[Alyssa Rosenzweig]

On Mon, 28 Apr 2025 14:31:32 +0200, Petr Mladek wrote:
> The generic FourCC format always prints the data using the big endian
> order. It is generic because it allows to read the data using a custom
> ordering.
> 
> The current code uses "n" for reading data in the reverse host ordering.
> It makes the 4 variants [hnbl] consistent with the generic printing
> of IPv4 addresses.
> 
> [...]

Applied, thanks!

[1/1] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering
      commit: 37eed892cc5ff36aeee59bb78f6aa417a44030a9

Best regards,
-- 
Alyssa Rosenzweig <alyssa@rosenzweig.io>

[PATCH] checkpatch: remove %p4cn

[Aditya Garg]

%p4cn was recently removed and replaced by %p4chR in vsprintf. So,
remove the check for %p4cn from checkpatch.pl.

Fixes: 37eed892cc5f ("vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering")

Signed-off-by: Aditya Garg <gargaditya08@live.com>
---
 scripts/checkpatch.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 44e233b6f..f79f0a085 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6891,7 +6891,7 @@ sub process {
 					    ($extension eq "f" &&
 					     defined $qualifier && $qualifier !~ /^w/) ||
 					    ($extension eq "4" &&
-					     defined $qualifier && $qualifier !~ /^c[hnlbc]/)) {
+					     defined $qualifier && $qualifier !~ /^c[hlbc]/)) {
 						$bad_specifier = $specifier;
 						last;
 					}
-- 
2.49.0

Re: [PATCH] checkpatch: remove %p4cn

[Joe Perches]

On Tue, 2025-04-29 at 16:07 +0000, Aditya Garg wrote:
> %p4cn was recently removed and replaced by %p4chR in vsprintf. So,
> remove the check for %p4cn from checkpatch.pl.
> 
> Fixes: 37eed892cc5f ("vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering")
> 
> Signed-off-by: Aditya Garg <gargaditya08@live.com>
> ---
>  scripts/checkpatch.pl | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 44e233b6f..f79f0a085 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6891,7 +6891,7 @@ sub process {
>  					    ($extension eq "f" &&
>  					     defined $qualifier && $qualifier !~ /^w/) ||
>  					    ($extension eq "4" &&
> -					     defined $qualifier && $qualifier !~ /^c[hnlbc]/)) {
> +					     defined $qualifier && $qualifier !~ /^c[hlbc]/)) {

Probably needs to be something like:

					$qualifier !~ /^c(?:[hlbc]|cR)$/

>  						$bad_specifier = $specifier;
>  						last;
>  					}

Re: [PATCH] checkpatch: remove %p4cn

[Aditya Garg]

On 29-04-2025 11:05 pm, Joe Perches wrote:
> On Tue, 2025-04-29 at 16:07 +0000, Aditya Garg wrote:
>> %p4cn was recently removed and replaced by %p4chR in vsprintf. So,
>> remove the check for %p4cn from checkpatch.pl.
>>
>> Fixes: 37eed892cc5f ("vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering")
>>
>> Signed-off-by: Aditya Garg <gargaditya08@live.com>
>> ---
>>  scripts/checkpatch.pl | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
>> index 44e233b6f..f79f0a085 100755
>> --- a/scripts/checkpatch.pl
>> +++ b/scripts/checkpatch.pl
>> @@ -6891,7 +6891,7 @@ sub process {
>>  					    ($extension eq "f" &&
>>  					     defined $qualifier && $qualifier !~ /^w/) ||
>>  					    ($extension eq "4" &&
>> -					     defined $qualifier && $qualifier !~ /^c[hnlbc]/)) {
>> +					     defined $qualifier && $qualifier !~ /^c[hlbc]/)) {
> 
> Probably needs to be something like:
> 
> 					$qualifier !~ /^c(?:[hlbc]|cR)$/

 					$qualifier !~ /^c(?:[hlbc]|hR)$/
I'll send a v2
> 
>>  						$bad_specifier = $specifier;
>>  						last;
>>  					}
> 

[PATCH v3] checkpatch: remove %p4cn

[Aditya Garg]

%p4cn was recently removed and replaced by %p4chR in vsprintf. So,
remove the check for %p4cn from checkpatch.pl.

Fixes: 37eed892cc5f ("vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering")
Signed-off-by: Aditya Garg <gargaditya08@live.com>
---
v2: Add specific check for %p4chR as suggested by Joe Perches.
v3: Remove blank lines from the tag block.

 scripts/checkpatch.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 44e233b6f..d5bde8322 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6891,7 +6891,7 @@ sub process {
 					    ($extension eq "f" &&
 					     defined $qualifier && $qualifier !~ /^w/) ||
 					    ($extension eq "4" &&
-					     defined $qualifier && $qualifier !~ /^c[hnlbc]/)) {
+					     defined $qualifier && $qualifier !~ /^c(?:[hlbc]|hR)$/)) {
 						$bad_specifier = $specifier;
 						last;
 					}
-- 
2.49.0

Re: [PATCH v3] checkpatch: remove %p4cn

[Petr Mladek]

On Wed 2025-04-30 19:19:08, Aditya Garg wrote:
> %p4cn was recently removed and replaced by %p4chR in vsprintf. So,
> remove the check for %p4cn from checkpatch.pl.
> 
> Fixes: 37eed892cc5f ("vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering")
> Signed-off-by: Aditya Garg <gargaditya08@live.com>

Looks and works well:

Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>

Alyssa, could you please queue this one via drm-misc-next as well?

Best Regards,
Petr

PS: Aditya, thanks a lot for stepping in and providing this patch. Also
      thanks others for shaping in. I was not able to react quickly. I
      had technical problems with my workstation and public holidays.

Re: [PATCH v3] checkpatch: remove %p4cn

[Alyssa Rosenzweig]

On Wed, 30 Apr 2025 19:19:08 +0530, Aditya Garg wrote:
> %p4cn was recently removed and replaced by %p4chR in vsprintf. So,
> remove the check for %p4cn from checkpatch.pl.
> 
> 

Applied, thanks!

[1/1] checkpatch: remove %p4cn
      commit: a6c0a91ccb257eaec2aee080df06863ce7601315

Best regards,
-- 
Alyssa Rosenzweig <alyssa@rosenzweig.io>

[PATCH v2] checkpatch: remove %p4cn and add check for %p4chR

[Aditya Garg]

%p4cn was recently removed and replaced by %p4chR in vsprintf. So,
remove the check for %p4cn from checkpatch.pl.

Fixes: 37eed892cc5f ("vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering")

Signed-off-by: Aditya Garg <gargaditya08@live.com>
---
v2: Add specific check for %p4chR as suggested by Joe Perches.

 scripts/checkpatch.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 44e233b6f..d5bde8322 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6891,7 +6891,7 @@ sub process {
 					    ($extension eq "f" &&
 					     defined $qualifier && $qualifier !~ /^w/) ||
 					    ($extension eq "4" &&
-					     defined $qualifier && $qualifier !~ /^c[hnlbc]/)) {
+					     defined $qualifier && $qualifier !~ /^c(?:[hlbc]|hR)$/)) {
 						$bad_specifier = $specifier;
 						last;
 					}
-- 
2.49.0

Re: [PATCH v2] checkpatch: remove %p4cn and add check for %p4chR

[Andy Shevchenko]

On Tue, Apr 29, 2025 at 05:50:30PM +0000, Aditya Garg wrote:
> %p4cn was recently removed and replaced by %p4chR in vsprintf. So,
> remove the check for %p4cn from checkpatch.pl.

...

> Fixes: 37eed892cc5f ("vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering")

> 

There shouldn't be blank lines in the tag block.

> Signed-off-by: Aditya Garg <gargaditya08@live.com>

-- 
With Best Regards,
Andy Shevchenko