linux-kernel - Re: [PATCH] media: s5p-jpeg: change "RST" to "RSET" to fix build warnings

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Date:   Mon, 6 Sep 2021 08:51:53 +0200
From:   Mauro Carvalho Chehab <mchehab@...nel.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>,
        linux-media@...r.kernel.org,
        Andrzej Pietrasiewicz <andrzejtp2010@...il.com>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] media: s5p-jpeg: change "RST" to "RSET" to fix build
 warnings

Em Sun,  5 Sep 2021 16:57:15 -0700
Randy Dunlap <rdunlap@...radead.org> escreveu:

> The use of a macro named 'RST' conflicts with one of the same name
> in arch/mips/include/asm/mach-rc32434/rb.h. This causes build
> warnings on some MIPS builds.
> 
> Change the use of RST to the name RSET.
> 
> Fixes these build warnings:
> 
> In file included from ../drivers/media/platform/s5p-jpeg/jpeg-hw-exynos3250.c:14:
> ../drivers/media/platform/s5p-jpeg/jpeg-core.h:43: warning: "RST" redefined
>    43 | #define RST                             0xd0
>       | 
> ../arch/mips/include/asm/mach-rc32434/rb.h:13: note: this is the location of the previous definition
>    13 | #define RST             (1 << 15)
> 
> In file included from ../drivers/media/platform/s5p-jpeg/jpeg-hw-s5p.c:13:
> ../drivers/media/platform/s5p-jpeg/jpeg-core.h:43: warning: "RST" redefined
>    43 | #define RST                             0xd0
> ../arch/mips/include/asm/mach-rc32434/rb.h:13: note: this is the location of the previous definition
>    13 | #define RST             (1 << 15)
> 
> In file included from ../drivers/media/platform/s5p-jpeg/jpeg-hw-exynos4.c:12:
> ../drivers/media/platform/s5p-jpeg/jpeg-core.h:43: warning: "RST" redefined
>    43 | #define RST                             0xd0
> ../arch/mips/include/asm/mach-rc32434/rb.h:13: note: this is the location of the previous definition
>    13 | #define RST             (1 << 15)
> 
> In file included from ../drivers/media/platform/s5p-jpeg/jpeg-core.c:31:
> ../drivers/media/platform/s5p-jpeg/jpeg-core.h:43: warning: "RST" redefined
>    43 | #define RST                             0xd0
> ../arch/mips/include/asm/mach-rc32434/rb.h:13: note: this is the location of the previous definition
>    13 | #define RST             (1 << 15)
> 
> Fixes: bb677f3ac434 ("[media] Exynos4 JPEG codec v4l2 driver")
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> Cc: Mauro Carvalho Chehab <mchehab@...nel.org>
> Cc: linux-media@...r.kernel.org
> Cc: Andrzej Pietrasiewicz <andrzejtp2010@...il.com>
> Cc: Jacek Anaszewski <jacek.anaszewski@...il.com>
> Cc: Sylwester Nawrocki <s.nawrocki@...sung.com>
> Cc: linux-arm-kernel@...ts.infradead.org
> ---
>  drivers/media/platform/s5p-jpeg/jpeg-core.c |    2 +-
>  drivers/media/platform/s5p-jpeg/jpeg-core.h |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> --- linux-next-20210903.orig/drivers/media/platform/s5p-jpeg/jpeg-core.c
> +++ linux-next-20210903/drivers/media/platform/s5p-jpeg/jpeg-core.c
> @@ -1203,7 +1203,7 @@ static bool s5p_jpeg_parse_hdr(struct s5
>  			break;
>  
>  		/* skip payload-less markers */
> -		case RST ... RST + 7:
> +		case RSET ... RSET + 7:
>  		case SOI:
>  		case EOI:
>  		case TEM:
> --- linux-next-20210903.orig/drivers/media/platform/s5p-jpeg/jpeg-core.h
> +++ linux-next-20210903/drivers/media/platform/s5p-jpeg/jpeg-core.h
> @@ -40,7 +40,7 @@
>  #define TEM				0x01
>  #define SOF0				0xc0
>  #define DHT				0xc4
> -#define RST				0xd0
> +#define RSET				0xd0
>  #define SOI				0xd8
>  #define EOI				0xd9
>  #define	SOS				0xda

I don't like this change, for a couple reasons:

1. the JPEG marker is "RST" (actually, "RST0") instead of "RSET" 
   (see pag. 36 https://www.w3.org/Graphics/JPEG/itu-t81.pdf). The
   close it sticks with the JPEG standard, the better;

2. better to add a namespace here, as other JPEG markers like SOS,
   SOI and EOI seems to have a high chance of happening somewhere
   else on other kernel headers in the future.

So, IMO, the best would be to rename all those markers as a hole, with
something similar to:

	$ for i in TEM SOF0 DHT RST SOI EOI SOS DQT DHP; do sed "s,\b$i\b,JPEG_MARKER_$i,g" -i drivers/media/platform/s5p-jpeg/*.[ch]; done

and manually adjust the patch, as at least this hunk could be
improved:

	@@ -187,11 +187,11 @@ struct s5p_jpeg_marker {
	  * @fmt:       driver-specific format of this queue
	  * @w:         image width
	  * @h:         image height
	- * @sos:       SOS marker's position relative to the buffer beginning
	- * @dht:       DHT markers' positions relative to the buffer beginning
	- * @dqt:       DQT markers' positions relative to the buffer beginning
	- * @sof:       SOF0 marker's position relative to the buffer beginning
	- * @sof_len:   SOF0 marker's payload length (without length field itself)
	+ * @sos:       JPEG_MARKER_SOS marker's position relative to the buffer beginning
	+ * @dht:       JPEG_MARKER_DHT markers' positions relative to the buffer beginning
	+ * @dqt:       JPEG_MARKER_DQT markers' positions relative to the buffer beginning
	+ * @sof:       JPEG_MARKER_SOF0 marker's position relative to the buffer beginning
	+ * @sof_len:   JPEG_MARKER_SOF0 marker's payload length (without length field itself)
	  * @size:      image buffer size in bytes
	  */

to avoid repeating the word marker.

Thanks,
Mauro