设计专业干货推荐网站,广州软件园 网站建设,ps做网站显示内容参考,搭建电商系统本系列文章基于linux 5.15 在上一篇文章DRM系列七#xff1a;Drm之DRM_IOCTL_MODE_CREATE_DUMB获取buf的handle和pitch之后#xff0c;接着使用ioctl(fd, DRM_IOCTL_MODE_ADDFB2, fb_cmd)创建一个新的帧缓冲区对象#xff08;framebuffer object),并将帧缓冲区对象与显…本系列文章基于linux 5.15 在上一篇文章DRM系列七Drm之DRM_IOCTL_MODE_CREATE_DUMB获取buf的handle和pitch之后接着使用ioctl(fd, DRM_IOCTL_MODE_ADDFB2, fb_cmd)创建一个新的帧缓冲区对象framebuffer object),并将帧缓冲区对象与显存关联起来。
一、整体流程
用户层提供width、height、piexel_format、handle和pitch然后调用ioctl(fd, DRM_IOCTL_MODE_ADDFB2, fb_cmd)进入kernel层调用drm_mode_addfb2_ioctl创建新的帧缓冲区对象framebuffer object并将其与显存中的一块内存区域关联起来,返回fb_id供用户层使用。其关系如下图所示
1.drm_mode_addfb2_ioctl
主要作用是为用户空间的应用程序创建一个新的帧缓冲区对象framebuffer object并将其与显存中的一块内存区域关联起来。
DRM_IOCTL_DEF(DRM_IOCTL_MODE_ADDFB2, drm_mode_addfb2_ioctl, 0),int drm_mode_addfb2_ioctl(struct drm_device *dev,void *data, struct drm_file *file_priv)
{
#ifdef __BIG_ENDIANif (!dev-mode_config.quirk_addfb_prefer_host_byte_order) {DRM_DEBUG_KMS(addfb2 broken on bigendian);return -EOPNOTSUPP;}
#endifreturn drm_mode_addfb2(dev, data, file_priv);
}int drm_mode_addfb2(struct drm_device *dev,void *data, struct drm_file *file_priv)
{struct drm_mode_fb_cmd2 *r data;struct drm_framebuffer *fb;if (!drm_core_check_feature(dev, DRIVER_MODESET))return -EOPNOTSUPP;fb drm_internal_framebuffer_create(dev, r, file_priv);if (IS_ERR(fb))return PTR_ERR(fb);/*将新创建的 framebuffer 的 ID 存储到用户空间传递的 drm_mode_fb_cmd2 结构中以便用户空间可以引用该 framebuffer*/DRM_DEBUG_KMS([FB:%d]\n, fb-base.id);r-fb_id fb-base.id;/* 帧缓冲区被添加到drm_filefile_priv拥有的帧缓冲区列表中 */mutex_lock(file_priv-fbs_lock);list_add(fb-filp_head, file_priv-fbs);mutex_unlock(file_priv-fbs_lock);return 0;
}1.1drm_internal_framebuffer_create
创建一个 drm_framebuffer 对象并初始化接着会调用 framebuffer_check 函数对传入的参数进行检查确保参数有效最后调用dev-mode_config.funcs-fb_create回调返回一个 drm_framebuffer 对象。
struct drm_framebuffer *drm_internal_framebuffer_create(struct drm_device *dev,const struct drm_mode_fb_cmd2 *r,struct drm_file *file_priv)
{struct drm_mode_config *config dev-mode_config;struct drm_framebuffer *fb;int ret;if (r-flags ~(DRM_MODE_FB_INTERLACED | DRM_MODE_FB_MODIFIERS)) {DRM_DEBUG_KMS(bad framebuffer flags 0x%08x\n, r-flags);return ERR_PTR(-EINVAL);}/*mode_config的min_width和min_height和帧缓冲区对象的width和height的限制*/if ((config-min_width r-width) || (r-width config-max_width)) {DRM_DEBUG_KMS(bad framebuffer width %d, should be %d %d\n,r-width, config-min_width, config-max_width);return ERR_PTR(-EINVAL);}if ((config-min_height r-height) || (r-height config-max_height)) {DRM_DEBUG_KMS(bad framebuffer height %d, should be %d %d\n,r-height, config-min_height, config-max_height);return ERR_PTR(-EINVAL);}if (r-flags DRM_MODE_FB_MODIFIERS !dev-mode_config.allow_fb_modifiers) {DRM_DEBUG_KMS(driver does not support fb modifiers\n);return ERR_PTR(-EINVAL);}/*对传入的参数进行检查确保参数有效*/ret framebuffer_check(dev, r);if (ret)return ERR_PTR(ret);/*调用mode_config func的fb_create回调*/fb dev-mode_config.funcs-fb_create(dev, file_priv, r);if (IS_ERR(fb)) {DRM_DEBUG_KMS(could not create framebuffer\n);return fb;}return fb;
}1.1.1framebuffer_check
对传入的参数进行检查确保参数有效。
static int framebuffer_check(struct drm_device *dev,const struct drm_mode_fb_cmd2 *r)
{const struct drm_format_info *info;int i;/* check if the format is supported at all */if (!__drm_format_info(r-pixel_format)) {DRM_DEBUG_KMS(bad framebuffer format %p4cc\n,r-pixel_format);return -EINVAL;}if (r-width 0) {DRM_DEBUG_KMS(bad framebuffer width %u\n, r-width);return -EINVAL;}if (r-height 0) {DRM_DEBUG_KMS(bad framebuffer height %u\n, r-height);return -EINVAL;}/* 获取与之相关的像素格式信息 */info drm_get_format_info(dev, r);for (i 0; i info-num_planes; i) {unsigned int width fb_plane_width(r-width, info, i);unsigned int height fb_plane_height(r-height, info, i);unsigned int block_size info-char_per_block[i];u64 min_pitch drm_format_info_min_pitch(info, i, width);if (!block_size (r-modifier[i] DRM_FORMAT_MOD_LINEAR)) {DRM_DEBUG_KMS(Format requires non-linear modifier for plane %d\n, i);return -EINVAL;}if (!r-handles[i]) {DRM_DEBUG_KMS(no buffer object handle for plane %d\n, i);return -EINVAL;}if (min_pitch UINT_MAX)return -ERANGE;if ((uint64_t) height * r-pitches[i] r-offsets[i] UINT_MAX)return -ERANGE;if (block_size r-pitches[i] min_pitch) {DRM_DEBUG_KMS(bad pitch %u for plane %d\n, r-pitches[i], i);return -EINVAL;}if (r-modifier[i] !(r-flags DRM_MODE_FB_MODIFIERS)) {DRM_DEBUG_KMS(bad fb modifier %llu for plane %d\n,r-modifier[i], i);return -EINVAL;}if (r-flags DRM_MODE_FB_MODIFIERS r-modifier[i] ! r-modifier[0]) {DRM_DEBUG_KMS(bad fb modifier %llu for plane %d\n,r-modifier[i], i);return -EINVAL;}/* modifier specific checks: */switch (r-modifier[i]) {case DRM_FORMAT_MOD_SAMSUNG_64_32_TILE:/* NOTE: the pitch restriction may be lifted later if it turns* out that no hw has this restriction:*/if (r-pixel_format ! DRM_FORMAT_NV12 ||width % 128 || height % 32 ||r-pitches[i] % 128) {DRM_DEBUG_KMS(bad modifier data for plane %d\n, i);return -EINVAL;}break;default:break;}}for (i info-num_planes; i 4; i) {if (r-modifier[i]) {DRM_DEBUG_KMS(non-zero modifier for unused plane %d\n, i);return -EINVAL;}/* Pre-FB_MODIFIERS userspace didnt clear the structs properly. */if (!(r-flags DRM_MODE_FB_MODIFIERS))continue;if (r-handles[i]) {DRM_DEBUG_KMS(buffer object handle for unused plane %d\n, i);return -EINVAL;}if (r-pitches[i]) {DRM_DEBUG_KMS(non-zero pitch for unused plane %d\n, i);return -EINVAL;}if (r-offsets[i]) {DRM_DEBUG_KMS(non-zero offset for unused plane %d\n, i);return -EINVAL;}}return 0;
}1.1.1.1drm_get_format_info
用于根据用户空间提供的 framebuffer 创建请求drm_mode_fb_cmd2获取与之相关的像素格式信息。在这里会使用dev-mode_config.funcs-get_format_info回调。
const struct drm_format_info *drm_get_format_info(struct drm_device *dev,const struct drm_mode_fb_cmd2 *mode_cmd)
{const struct drm_format_info *info NULL;if (dev-mode_config.funcs-get_format_info)info dev-mode_config.funcs-get_format_info(mode_cmd);if (!info)info drm_format_info(mode_cmd-pixel_format);return info;
}
