linux-kernel - Re: [PATCH 2/2] drm/appletbdm: use %p4cl instead of %p4cc

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Message-ID: <be2f49b5-dcdc-4954-b650-90670dfa70b9@suse.de>
Date: Wed, 12 Mar 2025 12:51:33 +0100
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Aditya Garg <gargaditya08@...e.com>, Aun-Ali Zaidi <admin@...eit.net>,
 Maxime Ripard <mripard@...nel.org>, "airlied@...hat.com"
 <airlied@...hat.com>, Simona Vetter <simona@...ll.ch>,
 "andriy.shevchenko@...ux.intel.com" <andriy.shevchenko@...ux.intel.com>,
 Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>,
 Rasmus Villemoes <linux@...musvillemoes.dk>,
 "senozhatsky@...omium.org" <senozhatsky@...omium.org>,
 Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>,
 "apw@...onical.com" <apw@...onical.com>, "joe@...ches.com"
 <joe@...ches.com>, "dwaipayanray1@...il.com" <dwaipayanray1@...il.com>,
 "lukas.bulwahn@...il.com" <lukas.bulwahn@...il.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
 "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
 Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>,
 Asahi Linux Mailing List <asahi@...ts.linux.dev>
Subject: Re: [PATCH 2/2] drm/appletbdm: use %p4cl instead of %p4cc

Hi

Am 12.03.25 um 10:06 schrieb Aditya Garg:
> From: Aditya Garg <gargaditya08@...e.com>
>
> Due to lack of a proper printk format, %p4cc was being used instead of
> %p4cl for the purpose of printing FourCCs. But the disadvange was that
> they were being printed in a reverse order. %p4cl should correct this
> issue.
>
> Signed-off-by: Aditya Garg <gargaditya08@...e.com>
> ---
>   drivers/gpu/drm/tiny/appletbdrm.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/tiny/appletbdrm.c b/drivers/gpu/drm/tiny/appletbdrm.c
> index 703b9a41a..751b05753 100644
> --- a/drivers/gpu/drm/tiny/appletbdrm.c
> +++ b/drivers/gpu/drm/tiny/appletbdrm.c
> @@ -212,7 +212,7 @@ static int appletbdrm_read_response(struct appletbdrm_device *adev,
>   	}
>   
>   	if (response->msg != expected_response) {
> -		drm_err(drm, "Unexpected response from device (expected %p4cc found %p4cc)\n",
> +		drm_err(drm, "Unexpected response from device (expected %p4cl found %p4cl)\n",
>   			&expected_response, &response->msg);

If you want to print out protocol-header tokens, why not use formatting 
macros as we do with DRM mode? There's one for the format string [1] and 
one for the argument. [2] It's not as fancy as the conversion code, but 
you'll get something for your driver that is easily understandable.

[1] 
https://elixir.bootlin.com/linux/v6.14-rc4/source/include/drm/drm_modes.h#L425
[2] 
https://elixir.bootlin.com/linux/v6.14-rc4/source/include/drm/drm_modes.h#L431

Best regards
Thomas

>   		return -EIO;
>   	}
> @@ -286,7 +286,7 @@ static int appletbdrm_get_information(struct appletbdrm_device *adev)
>   	}
>   
>   	if (pixel_format != APPLETBDRM_PIXEL_FORMAT) {
> -		drm_err(drm, "Encountered unknown pixel format (%p4cc)\n", &pixel_format);
> +		drm_err(drm, "Encountered unknown pixel format (%p4cl)\n", &pixel_format);
>   		ret = -EINVAL;
>   		goto free_info;
>   	}

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)