Re: [PATCH 3/4] drm/fb-helper: Add module option to disable fbdev emulation

[Archit Taneja <architt@xxxxxxxxxxxxxx>]

On 08/25/2015 07:15 PM, Daniel Vetter wrote:
> Faster than recompiling.
>
> Note that restore_fbdev_mode_unlocked is a bit special and the only
> one which returns an error code when fbdev isn't there - i915 needs
> that one to not fall over with some additional fbcon related restore
> code. Everyone else just ignores the return value or only prints a
> DRM_DEBUG level message.

Reviewed-by:Archit Taneja <architt@xxxxxxxxxxxxxx>

> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
>   drivers/gpu/drm/drm_fb_helper.c | 29 +++++++++++++++++++++++++++++
>   1 file changed, 29 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 83aacb0cc9df..8259dec1de1f 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -39,6 +39,11 @@
>   #include <drm/drm_fb_helper.h>
>   #include <drm/drm_crtc_helper.h>
>
> +static bool drm_fbdev_emulation = true;
> +module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600);
> +MODULE_PARM_DESC(fbdev_emulation,
> +		 "Enable legacy fbdev emulation [default=true]");
> +
>   static LIST_HEAD(kernel_fb_helper_list);
>
>   /**
> @@ -99,6 +104,9 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
>   	struct drm_connector *connector;
>   	int i;
>
> +	if (!drm_fbdev_emulation)
> +		return 0;
> +
>   	mutex_lock(&dev->mode_config.mutex);
>   	drm_for_each_connector(connector, dev) {
>   		struct drm_fb_helper_connector *fb_helper_connector;
> @@ -129,6 +137,9 @@ int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper, struct drm_
>   	struct drm_fb_helper_connector **temp;
>   	struct drm_fb_helper_connector *fb_helper_connector;
>
> +	if (!drm_fbdev_emulation)
> +		return 0;
> +
>   	WARN_ON(!mutex_is_locked(&fb_helper->dev->mode_config.mutex));
>   	if (fb_helper->connector_count + 1 > fb_helper->connector_info_alloc_count) {
>   		temp = krealloc(fb_helper->connector_info, sizeof(struct drm_fb_helper_connector *) * (fb_helper->connector_count + 1), GFP_KERNEL);
> @@ -184,6 +195,9 @@ int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
>   	struct drm_fb_helper_connector *fb_helper_connector;
>   	int i, j;
>
> +	if (!drm_fbdev_emulation)
> +		return 0;
> +
>   	WARN_ON(!mutex_is_locked(&fb_helper->dev->mode_config.mutex));
>
>   	for (i = 0; i < fb_helper->connector_count; i++) {
> @@ -375,6 +389,9 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
>   	bool do_delayed
>   	int ret;
>
> +	if (!drm_fbdev_emulation)
> +		return -ENODEV;
> +
>   	drm_modeset_lock_all(dev);
>   	ret = restore_fbdev_mode(fb_helper);
>
> @@ -591,6 +608,9 @@ int drm_fb_helper_init(struct drm_device *dev,
>   	struct drm_crtc *crtc;
>   	int i;
>
> +	if (!drm_fbdev_emulation)
> +		return 0;
> +
>   	if (!max_conn_count)
>   		return -EINVAL;
>
> @@ -713,6 +733,9 @@ EXPORT_SYMBOL(drm_fb_helper_release_fbi);
>
>   void drm_fb_helper_fini(struct drm_fb_helper *fb_helper)
>   {
> +	if (!drm_fbdev_emulation)
> +		return;
> +
>   	if (!list_empty(&fb_helper->kernel_fb_list)) {
>   		list_del(&fb_helper->kernel_fb_list);
>   		if (list_empty(&kernel_fb_helper_list)) {
> @@ -1933,6 +1956,9 @@ int drm_fb_helper_initial_config(struct drm_fb_helper *fb_helper, int bpp_sel)
>   	struct drm_device *dev = fb_helper->dev;
>   	int count = 0;
>
> +	if (!drm_fbdev_emulation)
> +		return 0;
> +
>   	mutex_lock(&dev->mode_config.mutex);
>   	count = drm_fb_helper_probe_connector_modes(fb_helper,
>   						    dev->mode_config.max_width,
> @@ -1976,6 +2002,9 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
>   	struct drm_device *dev = fb_helper->dev;
>   	u32 max_width, max_height;
>
> +	if (!drm_fbdev_emulation)
> +		return 0;
> +
>   	mutex_lock(&fb_helper->dev->mode_config.mutex);
>   	if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) {
>   		fb_helper->delayed_hotplug = true;

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