Re: [RFC PATCH 1/3] drm/debugfs: create debugfs files during drm_dev_register().

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 13.05.20 um 13:41 schrieb Wambui Karuga:
> Introduce the ability to track requests for the addition of drm debugfs
> files at any time and have them added all at once during
> drm_dev_register().
> 
> Drivers can add drm debugfs file requests to a new list tied to drm_device.
> During drm_dev_register(), the new function drm_debugfs_create_file()
> will iterate over the list of added files on a given minor to create
> them.
> 
> Two new structs are introduced in this change: struct drm_simple_info
> which represents a drm debugfs file entry and struct
> drm_simple_info_entry which is used to track file requests and is the
> main parameter of choice passed by functions. Each drm_simple_info_entry is
> added to the new struct drm_device->debugfs_list for file requests.
> 
> Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
> ---
>  drivers/gpu/drm/drm_debugfs.c | 59 ++++++++++++++++++++++++++++++++---
>  drivers/gpu/drm/drm_drv.c     |  2 ++
>  include/drm/drm_debugfs.h     | 38 ++++++++++++++++++++++
>  include/drm/drm_device.h      | 12 +++++++
>  4 files changed, 107 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
> index 2bea22130703..03b0588ede68 100644
> --- a/drivers/gpu/drm/drm_debugfs.c
> +++ b/drivers/gpu/drm/drm_debugfs.c
> @@ -145,9 +145,10 @@ static const struct drm_info_list drm_debugfs_list[] = {
>  
>  static int drm_debugfs_open(struct inode *inode, struct file *file)
>  {
> -	struct drm_info_node *node = inode->i_private;
> +	struct drm_simple_info_entry *entry = inode->i_private;
> +	struct drm_simple_info *node = &entry->file;
>  
> -	return single_open(file, node->info_ent->show, node);
> +	return single_open(file, node->show_fn, entry);
>  }
>  
>  
> @@ -159,6 +160,25 @@ static const struct file_operations drm_debugfs_fops = {
>  	.release = single_release,
>  };
>  
> +/**
> + * drm_debugfs_create_file - create DRM debugfs file.
> + * @dev: drm_device that the file belongs to
> + *
> + * Create a DRM debugfs file from the list of files to be created
> + * from dev->debugfs_list.
> + */
> +static void drm_debugfs_create_file(struct drm_minor *minor)

This function creates several files. I'd rather call it
drm_debugfs_create_added_files().

> +{
> +	struct drm_device *dev = minor->dev;
> +	struct drm_simple_info_entry *entry;
> +
> +	list_for_each_entry(entry, &dev->debugfs_list, list) {
> +		debugfs_create_file(entry->file.name,
> +				    S_IFREG | S_IRUGO, minor->debugfs_root,
> +				    entry,
> +				    &drm_debugfs_fops);
> +	}

I think the created items should be removed from the list. That way,
drivers can call the function multiple times without recreating the same
files again.

> +}
>  
>  /**
>   * drm_debugfs_create_files - Initialize a given set of debugfs files for DRM
> @@ -213,8 +233,7 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
>  	sprintf(name, "%d", minor_id);
>  	minor->debugfs_root = debugfs_create_dir(name, root);
>  
> -	drm_debugfs_create_files(drm_debugfs_list, DRM_DEBUGFS_ENTRIES,
> -				 minor->debugfs_root, minor);

By removing these two lines, aren't you losing the files listed in
DRM_DEBUGFS_ENTRIES?

> +	drm_debugfs_create_file(minor);
>  
>  	if (drm_drv_uses_atomic_modeset(dev)) {
>  		drm_atomic_debugfs_init(minor);
> @@ -449,4 +468,36 @@ void drm_debugfs_crtc_remove(struct drm_crtc *crtc)
>  	crtc->debugfs_entry = NULL;
>  }
>  
> +void drm_debugfs_add_file(struct drm_device *dev, const char *name,
> +			  drm_simple_show_t show_fn, void *data)
> +{
> +	struct drm_simple_info_entry *entry =
> +		kzalloc(sizeof(*entry), GFP_KERNEL);
> +
> +	if (!entry)
> +		return;
> +
> +	entry->file.name = name;
> +	entry->file.show_fn = show_fn;
> +	entry->file.data = data;
> +	entry->dev = dev;
> +
> +	mutex_lock(&dev->debugfs_mutex);
> +	list_add(&entry->list, &dev->debugfs_list);
> +	mutex_unlock(&dev->debugfs_mutex);
> +}
> +EXPORT_SYMBOL(drm_debugfs_add_file);
> +
> +void drm_debugfs_add_files(struct drm_device *dev,
> +			   const struct drm_simple_info *files, int count)
> +{
> +	int i;
> +
> +	for (i = 0; i < count; i++) {
> +		drm_debugfs_add_file(dev, files[i].name, files[i].show_fn,
> +				     files[i].data);
> +	}
> +}
> +EXPORT_SYMBOL(drm_debugfs_add_files);
> +
>  #endif /* CONFIG_DEBUG_FS */
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index bc38322f306e..c68df4e31aa0 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -646,12 +646,14 @@ int drm_dev_init(struct drm_device *dev,
>  	INIT_LIST_HEAD(&dev->filelist_internal);
>  	INIT_LIST_HEAD(&dev->clientlist);
>  	INIT_LIST_HEAD(&dev->vblank_event_list);
> +	INIT_LIST_HEAD(&dev->debugfs_list);
>  
>  	spin_lock_init(&dev->event_lock);
>  	mutex_init(&dev->struct_mutex);
>  	mutex_init(&dev->filelist_mutex);
>  	mutex_init(&dev->clientlist_mutex);
>  	mutex_init(&dev->master_mutex);
> +	mutex_init(&dev->debugfs_mutex);
>  
>  	ret = drmm_add_action(dev, drm_dev_init_release, NULL);
>  	if (ret)
> diff --git a/include/drm/drm_debugfs.h b/include/drm/drm_debugfs.h
> index 2188dc83957f..bbce580c3b38 100644
> --- a/include/drm/drm_debugfs.h
> +++ b/include/drm/drm_debugfs.h
> @@ -34,6 +34,44 @@
>  
>  #include <linux/types.h>
>  #include <linux/seq_file.h>
> +
> +struct drm_device;
> +
> +typedef int (*drm_simple_show_t)(struct seq_file *, void *);
> +
> +/**
> + * struct drm_simple_info - debugfs file entry
> + *
> + * This struct represents a debugfs file to be created.
> + */
> +struct drm_simple_info {

drm_simple_info and drm_simple_info_entry seem to be misnomers. They
should probably have some reference to debugfs in their name.

Best regards
Thomas


> +	const char *name;
> +	drm_simple_show_t show_fn;
> +	u32 driver_features;
> +	void *data;
> +};
> +
> +/**
> + * struct drm_simple_info_entry - debugfs list entry
> + *
> + * This struct is used in tracking requests for new debugfs files
> + * to be created.
> + */
> +struct drm_simple_info_entry {
> +	struct drm_device *dev;
> +	struct drm_simple_info file;
> +	struct list_head list;
> +};
> +
> +void drm_debugfs_add_file(struct drm_device *dev,
> +			  const char *name,
> +			  drm_simple_show_t show_fn,
> +			  void *data);
> +
> +void drm_debugfs_add_files(struct drm_device *dev,
> +			   const struct drm_simple_info *files,
> +			   int count);
> +
>  /**
>   * struct drm_info_list - debugfs info list entry
>   *
> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index a55874db9dd4..b84dfdac27b7 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -326,6 +326,18 @@ struct drm_device {
>  	 */
>  	struct drm_fb_helper *fb_helper;
>  
> +	/**
> +	 * @debugfs_mutex:
> +	 * Protects debugfs_list access.
> +	 */
> +	struct mutex debugfs_mutex;
> +
> +	/** @debugfs_list:
> +	 * List of debugfs files to add.
> +	 * Files are added during drm_dev_register().
> +	 */
> +	struct list_head debugfs_list;
> +
>  	/* Everything below here is for legacy driver, never use! */
>  	/* private: */
>  #if IS_ENABLED(CONFIG_DRM_LEGACY)
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer


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