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Message-ID: <15166a78-b603-464a-8fa5-b7dd43d55029@suse.de>
Date: Fri, 7 Nov 2025 11:06:14 +0100
From: Thomas Zimmermann <tzimmermann@...e.de>
To: oushixiong1025@....com,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: Maxime Ripard <mripard@...nel.org>, David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, Shixiong Ou <oushixiong@...inos.cn>,
Tiger Liu <liuyihu@...inos.cn>
Subject: Re: [PATCH] drm/fb-helper: add fbdev screen expended mode display
support
Am 07.11.25 um 10:26 schrieb oushixiong1025@....com:
> From: Shixiong Ou <oushixiong@...inos.cn>
>
> Add fbdev screen extended mode display support
What? What is this about?
>
> Signed-off-by: Tiger Liu <liuyihu@...inos.cn>
> Signed-off-by: Shixiong Ou <oushixiong@...inos.cn>
> ---
> drivers/gpu/drm/drm_fb_helper.c | 143 ++++++++++++++++++++++++++++++--
> 1 file changed, 135 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 53e9dc0543de..a6ec03bf3aef 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -78,6 +78,17 @@ MODULE_PARM_DESC(drm_leak_fbdev_smem,
> "Allow unsafe leaking fbdev physical smem address [default=false]");
> #endif
>
> +#define SCREEN_CLONE 0x0
> +#define SCREEN_EXPAND_HORIZONTAL 0x1
> +#define SCREEN_EXPAND_VERTICAL 0x2
> +
> +static bool drm_fbdev_screen_expand_mode_enabled;
> +static int drm_fbdev_screen_mode = SCREEN_CLONE;
> +module_param_named(screen_mode, drm_fbdev_screen_mode, int, 0444);
> +MODULE_PARM_DESC(screen_mode,
> + "Screen display of the fbdev. [0 = clone(default), 1 = expand horizontally,"
> + "2 = expand vertically]");
> +
> static LIST_HEAD(kernel_fb_helper_list);
> static DEFINE_MUTEX(kernel_fb_helper_lock);
>
> @@ -1345,15 +1356,35 @@ int drm_fb_helper_set_par(struct fb_info *info)
> }
> EXPORT_SYMBOL(drm_fb_helper_set_par);
>
> -static void pan_set(struct drm_fb_helper *fb_helper, int dx, int dy)
> +static void pan_set_locked(struct drm_client_dev *client,
> + int dx, int dy)
> {
> struct drm_mode_set *mode_set;
> + int screen_x_offset = dx;
> + int screen_y_offset = dy;
>
> - mutex_lock(&fb_helper->client.modeset_mutex);
> - drm_client_for_each_modeset(mode_set, &fb_helper->client) {
> - mode_set->x += dx;
> - mode_set->y += dy;
> + drm_client_for_each_modeset(mode_set, client) {
> + if (drm_fbdev_screen_expand_mode_enabled) {
> + if (drm_fbdev_screen_mode == SCREEN_EXPAND_HORIZONTAL) {
> + mode_set->x += screen_x_offset;
> + mode_set->y += screen_y_offset;
> + screen_x_offset += mode_set->mode->hdisplay;
> + } else if (drm_fbdev_screen_mode == SCREEN_EXPAND_VERTICAL) {
> + mode_set->x += screen_x_offset;
> + mode_set->y += screen_y_offset;
> + screen_y_offset += mode_set->mode->vdisplay;
> + }
> + } else {
> + mode_set->x = screen_x_offset;
> + mode_set->y = screen_y_offset;
> + }
> }
> +}
> +
> +static void pan_set(struct drm_fb_helper *fb_helper, int dx, int dy)
> +{
> + mutex_lock(&fb_helper->client.modeset_mutex);
> + pan_set_locked(&fb_helper->client, dx, dy);
> mutex_unlock(&fb_helper->client.modeset_mutex);
> }
>
> @@ -1387,10 +1418,8 @@ static int pan_display_legacy(struct fb_var_screeninfo *var,
>
> mutex_lock(&client->modeset_mutex);
> drm_modeset_lock_all(fb_helper->dev);
> + pan_set_locked(client, var->xoffset, var->yoffset);
> drm_client_for_each_modeset(modeset, client) {
> - modeset->x = var->xoffset;
> - modeset->y = var->yoffset;
> -
> if (modeset->num_connectors) {
> ret = drm_mode_set_config_internal(modeset);
> if (!ret) {
> @@ -1461,6 +1490,94 @@ static uint32_t drm_fb_helper_find_format(struct drm_fb_helper *fb_helper, const
> return DRM_FORMAT_INVALID;
> }
>
> +/*
> + * Check if the device supports extended mode
> + *
> + * return true if the device supports extended mode,
> + * otherwise return false.
> + */
> +static bool drm_fb_helper_validate_extended_mode(struct drm_fb_helper *fb_helper,
> + struct drm_fb_helper_surface_size *sizes)
> +{
> + struct drm_client_dev *client = &fb_helper->client;
> + struct drm_device *dev = fb_helper->dev;
> + struct drm_mode_config *config = &dev->mode_config;
> + struct drm_mode_set *mode_set;
> + u32 crtc_count;
> +
> + drm_client_for_each_modeset(mode_set, client) {
> + crtc_count++;
> +
> + for (int j = 0; j < mode_set->num_connectors; j++) {
> + struct drm_connector *connector = mode_set->connectors[j];
> +
> + if (connector->has_tile) {
> + drm_dbg_kms(client->dev,
> + "Don't support extended with tile mode connector yet\n");
> + return false;
> + }
> + }
> + }
> +
> + if (crtc_count < 2) {
> + drm_dbg_kms(client->dev,
> + "Only support extended mode when device have mult-crtcs\n");
> + return false;
> + }
> +
> + if (drm_fbdev_screen_mode == SCREEN_EXPAND_HORIZONTAL) {
> + u32 x = 0;
> +
> + drm_client_for_each_modeset(mode_set, client) {
> + struct drm_display_mode *desired_mode;
> +
> + desired_mode = mode_set->mode;
> + x = mode_set->x;
> + sizes->fb_width = sizes->surface_width += desired_mode->hdisplay;
> + sizes->surface_height =
> + min_t(u32, desired_mode->vdisplay + mode_set->y,
> + sizes->surface_height);
> + sizes->fb_height = min_t(u32, desired_mode->vdisplay + mode_set->y,
> + sizes->fb_height);
> + }
> + sizes->fb_width = sizes->surface_width += x;
> +
> + if (sizes->fb_width > config->max_width) {
> + drm_dbg_kms(client->dev,
> + "screen_buffer total width %d > config width %d\n",
> + sizes->fb_width, config->max_width);
> + return false;
> + }
> + } else if (drm_fbdev_screen_mode == SCREEN_EXPAND_VERTICAL) {
> + u32 y = 0;
> +
> + drm_client_for_each_modeset(mode_set, client) {
> + struct drm_display_mode *desired_mode;
> +
> + desired_mode = mode_set->mode;
> + y = mode_set->y;
> + sizes->fb_height = sizes->surface_height += desired_mode->vdisplay;
> + sizes->surface_width =
> + min_t(u32, desired_mode->hdisplay + mode_set->x,
> + sizes->surface_width);
> + sizes->fb_width = min_t(u32, desired_mode->hdisplay + mode_set->x,
> + sizes->fb_width);
> + }
> + sizes->fb_height = sizes->surface_height += y;
> +
> + if (sizes->fb_height > config->max_height) {
> + drm_dbg_kms(client->dev,
> + "screen_buffer_total_height %d > config height %d\n",
> + sizes->fb_height, config->max_height);
> + return false;
> + }
> + } else {
> + return false;
> + }
> +
> + return true;
> +}
> +
> static int __drm_fb_helper_find_sizes(struct drm_fb_helper *fb_helper,
> struct drm_fb_helper_surface_size *sizes)
> {
> @@ -1527,6 +1644,16 @@ static int __drm_fb_helper_find_sizes(struct drm_fb_helper *fb_helper,
>
> /* first up get a count of crtcs now in use and new min/maxes width/heights */
> crtc_count = 0;
> +
> + /* Check if we support extended mode. If we do, we will adjust the sizes accordingly. */
> + if (drm_fbdev_screen_mode &&
> + drm_fb_helper_validate_extended_mode(fb_helper, sizes)) {
> + drm_fbdev_screen_expand_mode_enabled = true;
> + drm_dbg_kms(dev, "Extended mode: horizontal expansion, width: %d, height: %d\n",
> + sizes->surface_width, sizes->surface_height);
> + return 0;
> + }
> +
> drm_client_for_each_modeset(mode_set, client) {
> struct drm_display_mode *desired_mode;
> int x, y, j;
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)
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