linux-kernel - Re: [RFC 1/1] drm/mipi-dbi: Use drm_device for debugfs, drop drm_minor and .debugfs

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Message-ID: <lhjibofycex36n23edeb6m7uc4n55nqg4y3qdzoe2wdpc5twrh@ytyvawvgdhuz>
Date: Mon, 21 Apr 2025 13:29:44 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Jagath Jog J <jagathjog1996@...il.com>
Cc: mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com,
        simona@...ll.ch, mcanal@...lia.com, maarten.lankhorst@...ux.intel.com,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 1/1] drm/mipi-dbi: Use drm_device for debugfs, drop
 drm_minor and .debugfs_init

On Mon, Apr 21, 2025 at 02:29:07PM +0530, Jagath Jog J wrote:
> Refactor to use drm_device.debugfs_root instead of drm_minor for
> debugfs file creation. The driver can now initialize debugfs directly
> in probe(), before drm_dev_register(). This also removes the use of
> .debugfs_init callback.

Why? The callback was designed to add debugfs files. Likewise most if
not all DRM drivers add files under the corresponding minor node.

> 
> Signed-off-by: Jagath Jog J <jagathjog1996@...il.com>
> ---
>  drivers/gpu/drm/drm_mipi_dbi.c        | 8 ++++----
>  drivers/gpu/drm/tiny/ili9163.c        | 3 ++-
>  drivers/gpu/drm/tiny/panel-mipi-dbi.c | 3 ++-
>  include/drm/drm_mipi_dbi.h            | 4 ++--
>  4 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
> index 89e05a5bed1d..66f292c48a78 100644
> --- a/drivers/gpu/drm/drm_mipi_dbi.c
> +++ b/drivers/gpu/drm/drm_mipi_dbi.c
> @@ -1488,17 +1488,17 @@ static const struct file_operations mipi_dbi_debugfs_command_fops = {
>   *
>   * This function creates a 'command' debugfs file for sending commands to the
>   * controller or getting the read command values.
> - * Drivers can use this as their &drm_driver->debugfs_init callback.
> + * Drivers can call this function before registering their device to drm.
>   *
>   */
> -void mipi_dbi_debugfs_init(struct drm_minor *minor)
> +void mipi_dbi_debugfs_init(struct mipi_dbi_dev *dbidev)
>  {
> -	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(minor->dev);
>  	umode_t mode = S_IFREG | S_IWUSR;
>  
>  	if (dbidev->dbi.read_commands)
>  		mode |= S_IRUGO;
> -	debugfs_create_file("command", mode, minor->debugfs_root, dbidev,
> +
> +	debugfs_create_file("command", mode, dbidev->drm.debugfs_root, dbidev,
>  			    &mipi_dbi_debugfs_command_fops);
>  }
>  EXPORT_SYMBOL(mipi_dbi_debugfs_init);
> diff --git a/drivers/gpu/drm/tiny/ili9163.c b/drivers/gpu/drm/tiny/ili9163.c
> index 62cadf5e033d..351d2a5b9f27 100644
> --- a/drivers/gpu/drm/tiny/ili9163.c
> +++ b/drivers/gpu/drm/tiny/ili9163.c
> @@ -115,7 +115,6 @@ static struct drm_driver ili9163_driver = {
>  	.fops			= &ili9163_fops,
>  	DRM_GEM_DMA_DRIVER_OPS_VMAP,
>  	DRM_FBDEV_DMA_DRIVER_OPS,
> -	.debugfs_init		= mipi_dbi_debugfs_init,
>  	.name			= "ili9163",
>  	.desc			= "Ilitek ILI9163",
>  	.major			= 1,
> @@ -182,6 +181,8 @@ static int ili9163_probe(struct spi_device *spi)
>  
>  	drm_mode_config_reset(drm);
>  
> +	mipi_dbi_debugfs_init(dbidev);
> +
>  	ret = drm_dev_register(drm, 0);
>  	if (ret)
>  		return ret;
> diff --git a/drivers/gpu/drm/tiny/panel-mipi-dbi.c b/drivers/gpu/drm/tiny/panel-mipi-dbi.c
> index 0460ecaef4bd..94466dd8db9f 100644
> --- a/drivers/gpu/drm/tiny/panel-mipi-dbi.c
> +++ b/drivers/gpu/drm/tiny/panel-mipi-dbi.c
> @@ -267,7 +267,6 @@ static const struct drm_driver panel_mipi_dbi_driver = {
>  	.fops			= &panel_mipi_dbi_fops,
>  	DRM_GEM_DMA_DRIVER_OPS_VMAP,
>  	DRM_FBDEV_DMA_DRIVER_OPS,
> -	.debugfs_init		= mipi_dbi_debugfs_init,
>  	.name			= "panel-mipi-dbi",
>  	.desc			= "MIPI DBI compatible display panel",
>  	.major			= 1,
> @@ -384,6 +383,8 @@ static int panel_mipi_dbi_spi_probe(struct spi_device *spi)
>  
>  	drm_mode_config_reset(drm);
>  
> +	mipi_dbi_debugfs_init(dbidev);
> +
>  	ret = drm_dev_register(drm, 0);
>  	if (ret)
>  		return ret;
> diff --git a/include/drm/drm_mipi_dbi.h b/include/drm/drm_mipi_dbi.h
> index f45f9612c0bc..88a9c87a1e99 100644
> --- a/include/drm/drm_mipi_dbi.h
> +++ b/include/drm/drm_mipi_dbi.h
> @@ -230,9 +230,9 @@ int mipi_dbi_buf_copy(void *dst, struct iosys_map *src, struct drm_framebuffer *
>  })
>  
>  #ifdef CONFIG_DEBUG_FS
> -void mipi_dbi_debugfs_init(struct drm_minor *minor);
> +void mipi_dbi_debugfs_init(struct mipi_dbi_dev *dbidev);
>  #else
> -static inline void mipi_dbi_debugfs_init(struct drm_minor *minor) {}
> +static inline void mipi_dbi_debugfs_init(struct mipi_dbi_dev *dbidev) {}
>  #endif
>  
>  /**
> -- 
> 2.20.1
> 

-- 
With best wishes
Dmitry