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Message-ID: <376a4a95-5428-47d6-9da5-51c8141e71d1@kylinos.cn>
Date: Mon, 10 Nov 2025 13:54:04 +0800
From: Shixiong Ou <oushixiong@...inos.cn>
To: Thomas Zimmermann <tzimmermann@...e.de>, 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, Tiger Liu <liuyihu@...inos.cn>
Subject: Re: [PATCH] drm/fb-helper: add fbdev screen expended mode display
support
在 2025/11/7 18:06, Thomas Zimmermann 写道:
>
>
> 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?
>
If an fbdev device has multiple screens, they are mirrored by default.
This patch aims to enable extended display for the tty, allowing
horizontal or
vertical expansion to achieve a screen splicing effect in the tty terminal.
Best regards,
Shixiong
>>
>> 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;
>
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