linux-kernel - Re: [PATCH v2,2/7] media: mediatek: vcodec: Add debug params to control different log level

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Message-ID: <4da63f5b-87f3-89be-31fc-f574a1d7c9bd@collabora.com>
Date:   Wed, 22 Mar 2023 14:49:32 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Yunfei Dong <yunfei.dong@...iatek.com>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Nicolas Dufresne <nicolas@...fresne.ca>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Fritz Koenig <frkoenig@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Steve Cho <stevecho@...omium.org>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v2,2/7] media: mediatek: vcodec: Add debug params to
 control different log level

Il 22/03/23 10:46, Yunfei Dong ha scritto:
> Add parameter mtk_vcodec_dbg to open each codec log.
> Add parameter mtk_v4l2_dbg_level to open each instance log according to
> the parameter value.
> 
> Signed-off-by: Yunfei Dong <yunfei.dong@...iatek.com>
> ---
>   .../mediatek/vcodec/mtk_vcodec_dbgfs.c        |  2 ++
>   .../mediatek/vcodec/mtk_vcodec_util.c         |  8 ++++++
>   .../mediatek/vcodec/mtk_vcodec_util.h         | 25 ++++++++++++++++---
>   3 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dbgfs.c b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dbgfs.c
> index fb9edd379af5..b5093e4e4aa2 100644
> --- a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dbgfs.c
> +++ b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_dbgfs.c
> @@ -20,6 +20,8 @@ void mtk_vcodec_dbgfs_init(struct mtk_vcodec_dev *vcodec_dev)
>   			IS_ERR(vcodec_dev->dbgfs.vcodec_root));
>   
>   	vcodec_root = vcodec_dev->dbgfs.vcodec_root;
> +	debugfs_create_x32("mtk_v4l2_dbg_level", 0644, vcodec_root, &mtk_v4l2_dbg_level);
> +	debugfs_create_x32("mtk_vcodec_dbg", 0644, vcodec_root, &mtk_vcodec_dbg);
>   }
>   EXPORT_SYMBOL_GPL(mtk_vcodec_dbgfs_init);
>   
> diff --git a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_util.c b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_util.c
> index ace78c4b5b9e..f214e6f67005 100644
> --- a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_util.c
> +++ b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_util.c
> @@ -13,6 +13,14 @@
>   #include "mtk_vcodec_drv.h"
>   #include "mtk_vcodec_util.h"
>   
> +#if defined(CONFIG_DEBUG_FS)
> +int mtk_vcodec_dbg;
> +EXPORT_SYMBOL(mtk_vcodec_dbg);
> +
> +int mtk_v4l2_dbg_level;
> +EXPORT_SYMBOL(mtk_v4l2_dbg_level);
> +#endif
> +
>   void __iomem *mtk_vcodec_get_reg_addr(struct mtk_vcodec_ctx *data,
>   					unsigned int reg_idx)
>   {
> diff --git a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_util.h b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_util.h
> index 71956627a0e2..938f03cab3c9 100644
> --- a/drivers/media/platform/mediatek/vcodec/mtk_vcodec_util.h
> +++ b/drivers/media/platform/mediatek/vcodec/mtk_vcodec_util.h
> @@ -35,15 +35,34 @@ struct mtk_vcodec_dev;
>   	pr_err("[MTK_VCODEC][ERROR][%d]: " fmt "\n",		\
>   	       ((struct mtk_vcodec_ctx *)(h)->ctx)->id, ##args)
>   
> +#if defined(CONFIG_DEBUG_FS)
> +extern int mtk_v4l2_dbg_level;
> +extern int mtk_vcodec_dbg;
>   
> -#define mtk_v4l2_debug(level, fmt, args...) pr_debug(fmt, ##args)
> +#define mtk_v4l2_debug(level, fmt, args...)				 \
> +	do {								 \
> +		if (mtk_v4l2_dbg_level >= level)			 \
> +			pr_info("[MTK_V4L2] level=%d %s(),%d: " fmt "\n", \

These shall still be *debug* and not *info*, even if you're controlling the
log level from debugfs, as these are anyway debugging prints which can be
automatically optimized out for a kernel build with *no debug at all*.

The loglevel control is a commodity that should be meant to avoid too much
spam for readability and/or selectively enable "components" logging, because
then there's also the tracing framework providing maximum verbosity.

Besides, I'd be happy if this finally becomes dev_dbg instead of pr_debug.

Regards,
Angelo