[Intel-gfx] [RFC 2/3] drm: Register drmfs filesystem from drm init

[Daniel Vetter]

On Thu, Dec 01, 2016 at 01:44:16PM +0530, swati.dhingra at intel.com wrote:
> From: Swati Dhingra <swati.dhingra at intel.com>
> 
> During drm module initialization, drm_core_init initializes the drmfs
> filesystem and register this with kernel. A driver specific directory is created
> inside drmfs root, and dentry of this directory is saved for subsequent use
> by the driver (e.g. i915). The driver can then create files/directories inside
> this root directory directly.
> In case of i915 driver, the top directory is created at '/sys/kernel/drm/i915'.
> 
> Signed-off-by: Sourab Gupta <sourab.gupta at intel.com>
> Signed-off-by: Swati Dhingra <swati.dhingra at intel.com>
> ---
>  drivers/gpu/drm/drm_drv.c | 22 ++++++++++++++++++++++
>  include/drm/drm_drv.h     |  3 +++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 84fcfcb..ead360bd 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -688,6 +688,14 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
>  {
>  	int ret;
>  
> +#ifdef CONFIG_DRMFS
> +	dev->driver->drmfs_root = drmfs_create_dir(dev->driver->name, NULL);
> +	if (IS_ERR(dev->driver->drmfs_root)) {
> +		DRM_ERROR("Failed to get drmfs root dentry\n");
> +		return PTR_ERR(dev->driver->drmfs_root);
> +	}
> +#endif

Don't do #ifdef in the code, instead provide dummy static inline functions
that do nothing in headers when a feature is disabled. For an example see
CONFIG_DRM_FBDEV_EMULATION in drm_fb_helper.[hc].

Also, drmfs here is seriously lacking documentation. E.g. where are we
supposed to put different things related to rendering, modesetting, and
all these issues? You need to add a section in drm-uabi.rst, write
kernel-doc + overview sections for all of this and pull it in.
-Daniel

> +
>  	mutex_lock(&drm_global_mutex);
>  
>  	ret = drm_minor_register(dev, DRM_MINOR_CONTROL);
> @@ -758,6 +766,9 @@ void drm_dev_unregister(struct drm_device *dev)
>  	drm_minor_unregister(dev, DRM_MINOR_PRIMARY);
>  	drm_minor_unregister(dev, DRM_MINOR_RENDER);
>  	drm_minor_unregister(dev, DRM_MINOR_CONTROL);
> +#ifdef CONFIG_DRMFS
> +	drmfs_remove(dev->driver->drmfs_root);
> +#endif
>  }
>  EXPORT_SYMBOL(drm_dev_unregister);
>  
> @@ -825,6 +836,9 @@ static void drm_core_exit(void)
>  {
>  	unregister_chrdev(DRM_MAJOR, "drm");
>  	debugfs_remove(drm_debugfs_root);
> +#ifdef CONFIG_DRMFS
> +	drmfs_fini();
> +#endif
>  	drm_sysfs_destroy();
>  	idr_destroy(&drm_minors_idr);
>  	drm_connector_ida_destroy();
> @@ -845,6 +859,14 @@ static int __init drm_core_init(void)
>  		goto error;
>  	}
>  
> +#ifdef CONFIG_DRMFS
> +	ret = drmfs_init();
> +	if (ret < 0) {
> +		DRM_ERROR("Cannot create DRM FS: %d\n", ret);
> +		goto error;
> +	}
> +#endif
> +
>  	drm_debugfs_root = debugfs_create_dir("dri", NULL);
>  	if (!drm_debugfs_root) {
>  		ret = -ENOMEM;
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index aad8bba..34804de 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -403,6 +403,9 @@ struct drm_driver {
>  
>  	/* List of devices hanging off this driver with stealth attach. */
>  	struct list_head legacy_dev_list;
> +
> +	/* drmfs parent directory dentry for this driver */
> +	struct dentry *drmfs_root;
>  };
>  
>  extern __printf(6, 7)
> -- 
> 2.7.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch