Mesa初始化流程重学习之eglInitialize
引言
说来也惭愧，Mesa搞了这么久了，每次都想深入下，可是每次都是浅尝辄止了。这次趁着有了一定的闲暇时间并且有了调试景嘉微显卡的机会，还是想重新学习下，深入研究下！不说达到某个程度吗，至少能充实点！
这里我使用的mesa版本是22.3.7！其它版本可能存在一定差异，应该不大！
tree src/ -L 1
src/
├── amd
├── android_stub
├── asahi
├── broadcom
├── c11
├── compiler
├── drm-shim
├── egl
├── etnaviv
├── freedreno
├── gallium
├── gbm
├── getopt
├── glx
├── gtest
├── hgl
├── imagination
├── imgui
├── intel
├── loader
├── mapi
├── mesa
├── meson.build
├── microsoft
├── nouveau
├── panfrost
├── tool
├── util
├── virtio
└── vulkan29 directories, 1 filetree src/gallium/ -L 2
src/gallium/
├── auxiliary
│ ├── cso_cache
│ ├── draw
│ ├── driver_ddebug
│ ├── driver_noop
│ ├── driver_trace
│ ├── gallivm
│ ├── hud
│ ├── indices
│ ├── meson.build
│ ├── nir
│ ├── os
│ ├── pipebuffer
│ ├── pipe-loader
│ ├── postprocess
│ ├── renderonly
│ ├── rtasm
│ ├── target-helpers
│ ├── tessellator
│ ├── tgsi
│ ├── translate
│ ├── util
│ └── vl
├── drivers
│ ├── asahi
│ ├── crocus
│ ├── d3d12
│ ├── etnaviv
│ ├── freedreno
│ ├── i915
│ ├── iris
│ ├── lima
│ ├── llvmpipe
│ ├── xxx_gpu
│ ├── nouveau
│ ├── panfrost
│ ├── r300
│ ├── r600
│ ├── radeonsi
│ ├── softpipe
│ ├── svga
│ ├── tegra
│ ├── v3d
│ ├── vc4
│ ├── virgl
│ └── zink
├── frontends
│ ├── clover
│ ├── d3d10umd
│ ├── dri
│ ├── glx
│ ├── hgl
│ ├── lavapipe
│ ├── nine
│ ├── omx
│ ├── osmesa
│ ├── rusticl
│ ├── va
│ ├── vdpau
│ ├── wgl
│ └── xa
├── include
│ ├── frontend
│ ├── pipe
│ └── winsys
├── meson.build
├── README.portability
├── targets
│ ├── d3d10sw
│ ├── d3dadapter9
│ ├── dri
│ ├── dri-vdpau.dyn
│ ├── haiku-softpipe
│ ├── lavapipe
│ ├── libgl-gdi
│ ├── libgl-xlib
│ ├── omx
│ ├── opencl
│ ├── osmesa
│ ├── pipe-loader
│ ├── rusticl
│ ├── va
│ ├── vdpau
│ ├── wgl
│ └── xa
├── tests
│ ├── meson.build
│ ├── python
│ ├── trivial
│ └── unit
├── tools
│ ├── addr2line.sh
│ └── trace
└── winsys├── amdgpu├── asahi├── crocus├── d3d12├── etnaviv├── freedreno├── i915├── iris├── kmsro├── lima├── xxx_gpu├── nouveau├── panfrost├── radeon├── svga├── sw├── tegra├── v3d├── vc4└── virgl108 directories, 6 files一. 核心结构体和关系
_EGLDisplay和dri2_egl_display之间的关系
typedef struct _egl_display _EGLDisplay;struct _egl_display
{..._EGLPlatformType Platform; /**< The type of the platform display */void *PlatformDisplay; /**< A pointer to the platform display */_EGLDevice *Device; //这里的Driver指向_eglDriver，实现在Egl_dri2.cconst _EGLDriver *Driver; /**< Matched driver of the display */ .../* these fields are set by the driver during init */void *DriverData; /**< Driver private data */指向dri2_egl_display//disp->DriverData = (void *) dri2_dpy;_EGLExtensions Extensions; /**< Extensions supported */ ...
}struct dri2_egl_display
{const struct dri2_egl_display_vtbl *vtbl;mtx_t lock;int dri2_major;int dri2_minor;__DRIscreen *dri_screen; //这个screen很重要bool own_dri_screen;const __DRIconfig **driver_configs;void *driver;const __DRIcoreExtension *core; //这些会在初始化的时候被赋值，指向target的dri前端const __DRIimageDriverExtension *image_driver;const __DRIdri2Extension *dri2;const __DRIswrastExtension *swrast;const __DRIkopperExtension *kopper;const __DRI2flushExtension *flush;const __DRI2flushControlExtension *flush_control;const __DRItexBufferExtension *tex_buffer;const __DRIimageExtension *image;const __DRIrobustnessExtension *robustness;const __DRI2configQueryExtension *config;const __DRI2fenceExtension *fence;const __DRI2bufferDamageExtension *buffer_damage;const __DRI2blobExtension *blob;const __DRI2rendererQueryExtension *rendererQuery;const __DRI2interopExtension *interop;const __DRIconfigOptionsExtension *configOptions;const __DRImutableRenderBufferDriverExtension *mutable_render_buffer;int fd;/* dri2_initialize/dri2_terminate increment/decrement this count, so does* dri2_make_current (tracks if there are active contexts/surfaces). */int ref_count;bool own_device;bool invalidate_available;int min_swap_interval;int max_swap_interval;int default_swap_interval;
#ifdef HAVE_DRM_PLATFORMstruct gbm_dri_device *gbm_dri;
#endifchar *driver_name;const __DRIextension **loader_extensions;const __DRIextension **driver_extensions;#ifdef HAVE_X11_PLATFORMxcb_connection_t *conn;xcb_screen_t *screen;bool swap_available;
#ifdef HAVE_DRI3bool multibuffers_available;int dri3_major_version;int dri3_minor_version;int present_major_version;int present_minor_version;struct loader_dri3_extensions loader_dri3_ext;struct loader_dri3_screen_resources screen_resources;
#endif
#endif#ifdef HAVE_WAYLAND_PLATFORMstruct wl_display *wl_dpy;struct wl_display *wl_dpy_wrapper;struct wl_registry *wl_registry;struct wl_drm *wl_server_drm;struct wl_drm *wl_drm;uint32_t wl_drm_version, wl_drm_name;struct wl_shm *wl_shm;struct wl_event_queue *wl_queue;struct zwp_linux_dmabuf_v1 *wl_dmabuf;struct dri2_wl_formats formats;struct zwp_linux_dmabuf_feedback_v1 *wl_dmabuf_feedback;struct dmabuf_feedback_format_table format_table;bool authenticated;uint32_t capabilities;char *device_name;
#endif#ifdef HAVE_ANDROID_PLATFORMconst gralloc_module_t *gralloc;/* gralloc vendor usage bit for front rendering */uint32_t front_rendering_usage;
#endifbool is_render_node;bool is_different_gpu;
};可以通过_EGLDisplay的成员DriverData找到dri2_egl_display，并且dri2_dpy是一个非常重要的结构体！
_EGLDisplay *disp
struct dri2_egl_display *dri2_dpy = dri2_egl_display(disp);
__DRIscreen dri_screen pipe_screen之间关联
各种srceend的起点，是从dri2_egl_display开始的，它们之间的关联如下:
struct dri2_egl_display
{...__DRIscreen *dri_screen;...
}//这块image_driver和dri2的extensions怎么赋值来的，后面会具体分析
dri2_dpy->dri_screen = dri2_dpy->image_driver->createNewScreen2(...)或者
dri2_dpy->dri_screen = dri2_dpy->dri2->createNewScreen2(...)我们接下来看看__DRIscreen的定义
typedef struct __DRIscreenRec __DRIscreen;struct __DRIscreenRec {/**static const struct __DRIDriverVtableExtensionRec galliumdrm_vtable = {.base = { __DRI_DRIVER_VTABLE, 1 },.vtable = &galliumdrm_driver_api,}; 这里的driver指向galliumdrm_driver_apipsp->driver =((__DRIDriverVtableExtension *)driver_extensions[i])->vtable; **/const struct __DriverAPIRec *driver;int myNum;int fd;void *driverPrivate;void *loaderPrivate;const __DRIextension **extensions;const __DRIswrastLoaderExtension *swrast_loader;const __DRIkopperLoaderExtension *kopper_loader;struct {const __DRIdri2LoaderExtension *loader;const __DRIimageLookupExtension *image;const __DRIuseInvalidateExtension *useInvalidate;const __DRIbackgroundCallableExtension *backgroundCallable;} dri2;struct {const __DRIimageLoaderExtension *loader;} image;struct {const __DRImutableRenderBufferLoaderExtension *loader;} mutableRenderBuffer;driOptionCache optionInfo;driOptionCache optionCache;unsigned int api_mask;
};
结构体dri_screen定义:
struct dri_screen
{struct st_manager base;__DRIscreen *sPriv;//指向__DRIscreenboolean throttle;struct st_config_options options;/* Which postprocessing filters are enabled. */unsigned pp_enabled[PP_FILTERS];/* drm */int fd;boolean can_share_buffer;struct pipe_loader_device *dev;/* hooks filled in by dri2 & drisw */__DRIimage * (*lookup_egl_image)(struct dri_screen *ctx, void *handle);boolean (*validate_egl_image)(struct dri_screen *ctx, void *handle);__DRIimage * (*lookup_egl_image_validated)(struct dri_screen *ctx, void *handle);/* DRI exts that vary based on gallium pipe_screen caps. */__DRIimageExtension image_extension;__DRI2bufferDamageExtension buffer_damage_extension;/* DRI exts on this screen. Populated at init time based on device caps. */const __DRIextension *screen_extensions[14];...};struct st_manager
{struct pipe_screen *screen;//这里又和pipe_screen勾搭上了...
}dri_screen和__DRIscreen是如何建立联系的，或者说他们之间的关系是什么:
__DRIscreen * sPriv
struct dri_screen *screen;
struct pipe_screen *pscreen = NULL;screen->sPriv = sPriv;
sPriv->driverPrivate = (void *)screen;
真可以说的上是你中有我，我中有你的典范啊。相互关联对方！
dri_screen和pipe_screen是如何建立联系的，或者说他们之间的关系是什么:
这里就不兜圈子了，直接上关系:
//src/gallium/frontends/dri/dri_screen.c
const __DRIconfig **
dri_init_screen_helper(struct dri_screen *screen,struct pipe_screen *pscreen)
{screen->base.screen = pscreen;...
}
最后可以得到如下的一张关系表，其中厂家会对dri_screen进行扩展，通过结构体的继承
二.Mesa下eglInitialize初始化流程
搞通了这个流程，基本把Mesa的基本框架打通了。这里我们一步一步来分析，不具体代码详细分析，只有关键地方会详细分析：
//src/egl/drivers/dri2/egl_dri2.c
const _EGLDriver _eglDriver = {.Initialize = dri2_initialize,.Terminate = dri2_terminate,.CreateContext = dri2_create_context,.DestroyContext = dri2_destroy_context,.MakeCurrent = dri2_make_current,.CreateWindowSurface = dri2_create_window_surface,.CreatePixmapSurface = dri2_create_pixmap_surface,.CreatePbufferSurface = dri2_create_pbuffer_surface,.DestroySurface = dri2_destroy_surface,.GetProcAddress = dri2_get_proc_address,.WaitClient = dri2_wait_client,.WaitNative = dri2_wait_native,.BindTexImage = dri2_bind_tex_image,.ReleaseTexImage = dri2_release_tex_image,.SwapInterval = dri2_swap_interval,.SwapBuffers = dri2_swap_buffers,.SwapBuffersWithDamageEXT = dri2_swap_buffers_with_damage,.SwapBuffersRegionNOK = dri2_swap_buffers_region,.SetDamageRegion = dri2_set_damage_region,.PostSubBufferNV = dri2_post_sub_buffer,.CopyBuffers = dri2_copy_buffers,.QueryBufferAge = dri2_query_buffer_age,.CreateImageKHR = dri2_create_image,.DestroyImageKHR = dri2_destroy_image_khr,.CreateWaylandBufferFromImageWL = dri2_create_wayland_buffer_from_image,.QuerySurface = dri2_query_surface,.QueryDriverName = dri2_query_driver_name,.QueryDriverConfig = dri2_query_driver_config,
#ifdef HAVE_LIBDRM.CreateDRMImageMESA = dri2_create_drm_image_mesa,.ExportDRMImageMESA = dri2_export_drm_image_mesa,.ExportDMABUFImageQueryMESA = dri2_export_dma_buf_image_query_mesa,.ExportDMABUFImageMESA = dri2_export_dma_buf_image_mesa,.QueryDmaBufFormatsEXT = dri2_query_dma_buf_formats,.QueryDmaBufModifiersEXT = dri2_query_dma_buf_modifiers,
#endif
#ifdef HAVE_WAYLAND_PLATFORM.BindWaylandDisplayWL = dri2_bind_wayland_display_wl,.UnbindWaylandDisplayWL = dri2_unbind_wayland_display_wl,.QueryWaylandBufferWL = dri2_query_wayland_buffer_wl,
#endif.GetSyncValuesCHROMIUM = dri2_get_sync_values_chromium,.GetMscRateANGLE = dri2_get_msc_rate_angle,.CreateSyncKHR = dri2_create_sync,.ClientWaitSyncKHR = dri2_client_wait_sync,.SignalSyncKHR = dri2_signal_sync,.WaitSyncKHR = dri2_server_wait_sync,.DestroySyncKHR = dri2_destroy_sync,.GLInteropQueryDeviceInfo = dri2_interop_query_device_info,.GLInteropExportObject = dri2_interop_export_object,.GLInteropFlushObjects = dri2_interop_flush_objects,.DupNativeFenceFDANDROID = dri2_dup_native_fence_fd,.SetBlobCacheFuncsANDROID = dri2_set_blob_cache_funcs,
};
eglInitialize(...)//src/egl/main/eglapi.c_eglDriver.Initialize(disp)dri2_initialize(...)//src/egl/drivers/dri2/egl_dri2.cdri2_initialize_android(disp)//src/egl/drivers/dri2/platform_android.c这里我们对dri2_initialize_android拿出来，另开分析，只是让后面自己回过头看更加清楚！
dri2_initialize_android(_EGLDisplay *disp)struct dri2_egl_display *dri2_dpy;dri2_dpy = calloc(1, sizeof(*dri2_dpy));disp->DriverData = (void *) dri2_dpy;ret = hw_get_module(GRALLOC_HARDWARE_MODULE_ID,(const hw_module_t **)&dri2_dpy->gralloc);device_opened = droid_open_device(disp, disp->Options.ForceSoftware);dri2_dpy->vtbl = &droid_display_vtbl;droid_open_device(...)// src/egl/drivers/dri2/platform_android.cstruct dri2_egl_display *dri2_dpy = dri2_egl_display(disp)dri2_dpy->fd = loader_open_device(device->nodes[node_type])droid_probe_device(...)droid_load_driver(..)//这个非常重要，加载驱动dri2_dpy->loader_extensions = droid_image_loader_extensions;dri2_load_driver_dri3(...)dri2_create_screen(...)//构建screen，关于scrren的关系图前面已经放出来了,详见章节3我们接下来分析dri2_load_driver_dri3的调用流程，代码流程比较多，只能一步步的来:
static const struct dri2_extension_match dri3_driver_extensions[] = {{ __DRI_CORE, 1, offsetof(struct dri2_egl_display, core) },{ __DRI_IMAGE_DRIVER, 1, offsetof(struct dri2_egl_display, image_driver) },{ NULL, 0, 0 }
};
dri2_load_driver_dri3(...)//src/egl/drivers/dri2/egl_dri2.cdri2_load_driver_common(disp, dri3_driver_extensions)extensions = dri2_open_driver(disp)//详见章节2.1dri2_bind_extensions(dri2_dpy, driver_extensions, extensions, false)//详见章节2.2dri2_dpy->driver_extensions = extensions2.1 dri2_open_driver
我们接下来重点分析该函数:
dri2_open_driver()//src/egl/drivers/dri2/egl_dri2.cconst struct __DRIextensionRec **(*get_extensions)(void);void *driver = loader_open_driver_lib(driver_name, "_dri", search_path_vars,DEFAULT_DRIVER_DIR, true);//加载dri库get_extensions_name = loader_get_extensions_name(driver_name)//拼接驱动extensions名称，这里的拼接后是__driDriverGetExtensions_xxx_gpuget_extensions = dlsym(driver, get_extensions_name)//加载函数符号表等这里的__driDriverGetExtensions_xxx_gpu函数符号表是怎么拼凑成的了，如果我们通过grep在mesa搜索，怎么搜索也搜不到了。它是通过宏定义实现的。它的定义如下:
//src/gallium/targets/dri/target.c
#define DEFINE_LOADER_DRM_ENTRYPOINT(drivername) \
const __DRIextension **__driDriverGetExtensions_##drivername(void); \
PUBLIC const __DRIextension **__driDriverGetExtensions_##drivername(void) \
{ \return galliumdrm_driver_extensions; \
}#if defined(GALLIUM_MWV207)
DEFINE_LOADER_DRM_ENTRYPOINT(xxx_gpu); //这里我们也可以扩展，自己的驱动，譬如XXX参照这个
#endif
这里我们重点关注galliumdrm_driver_extensions的实现，我们接着继续往下看：
注意它的实现在代码是在frontends前端目录代码下
//src/gallium/frontends/dri/dri2.c
const __DRIextension *galliumdrm_driver_extensions[] = {&driCoreExtension.base,&driImageDriverExtension.base,&driDRI2Extension.base,&gallium_config_options.base,&galliumdrm_vtable.base,NULL
};//src/gallium/frontends/dri/dri_util.c
/** Core interface */
const __DRIcoreExtension driCoreExtension = {.base = { __DRI_CORE, 2 },.createNewScreen = NULL,.destroyScreen = driDestroyScreen,.getExtensions = driGetExtensions,.getConfigAttrib = driGetConfigAttrib,.indexConfigAttrib = driIndexConfigAttrib,.createNewDrawable = NULL,.destroyDrawable = driDestroyDrawable,.swapBuffers = driSwapBuffers, /* swrast */.createNewContext = driCreateNewContext, /* swrast */.copyContext = driCopyContext,.destroyContext = driDestroyContext,.bindContext = driBindContext,.unbindContext = driUnbindContext
};/** Image driver interface */
const __DRIimageDriverExtension driImageDriverExtension = {.base = { __DRI_IMAGE_DRIVER, 1 },.createNewScreen2 = driCreateNewScreen2,.createNewDrawable = driCreateNewDrawable,.getAPIMask = driGetAPIMask,.createContextAttribs = driCreateContextAttribs,
};/** DRI2 interface */
const __DRIdri2Extension driDRI2Extension = {.base = { __DRI_DRI2, 4 },.createNewScreen = dri2CreateNewScreen,.createNewDrawable = driCreateNewDrawable,.createNewContext = driCreateNewContext,.getAPIMask = driGetAPIMask,.createNewContextForAPI = driCreateNewContextForAPI,.allocateBuffer = dri2AllocateBuffer,.releaseBuffer = dri2ReleaseBuffer,.createContextAttribs = driCreateContextAttribs,.createNewScreen2 = driCreateNewScreen2,
};//src/gallium/frontends/dri/dri2.c
static const struct __DRIDriverVtableExtensionRec galliumdrm_vtable = {.base = { __DRI_DRIVER_VTABLE, 1 },.vtable = &galliumdrm_driver_api,
};
2.2 dri2_bind_extensions
我们接下来重点分析该函数:
static EGLBoolean
dri2_bind_extensions(struct dri2_egl_display *dri2_dpy,const struct dri2_extension_match *matches,const __DRIextension **extensions,bool optional)
{int ret = EGL_TRUE;void *field;for (int i = 0; extensions[i]; i++) {_eglLog(_EGL_DEBUG, "found extension `%s'", extensions[i]->name);for (int j = 0; matches[j].name; j++) {if (strcmp(extensions[i]->name, matches[j].name) == 0 &&extensions[i]->version >= matches[j].version) {field = ((char *) dri2_dpy + matches[j].offset);*(const __DRIextension **) field = extensions[i];_eglLog(_EGL_INFO, "found extension %s version %d",extensions[i]->name, extensions[i]->version);break;}}}for (int j = 0; matches[j].name; j++) {field = ((char *) dri2_dpy + matches[j].offset);if (*(const __DRIextension **) field == NULL) {if (optional) {_eglLog(_EGL_DEBUG, "did not find optional extension %s version %d",matches[j].name, matches[j].version);} else {_eglLog(_EGL_WARNING, "did not find extension %s version %d",matches[j].name, matches[j].version);ret = EGL_FALSE;}}}return ret;
}
我们可以理解这个函数，这个函数主要是填充dri2_egl_display中的各个extensions扩展，譬如:
//src/egl/drivers/dri2/egl_dri2.h
struct dri2_egl_display
{...const __DRIcoreExtension *core;const __DRIimageDriverExtension *image_driver;const __DRIdri2Extension *dri2;const __DRIswrastExtension *swrast;const __DRIkopperExtension *kopper;const __DRI2flushExtension *flush;const __DRI2flushControlExtension *flush_control;const __DRItexBufferExtension *tex_buffer;const __DRIimageExtension *image;const __DRIrobustnessExtension *robustness;const __DRI2configQueryExtension *config;const __DRI2fenceExtension *fence;const __DRI2bufferDamageExtension *buffer_damage;const __DRI2blobExtension *blob;const __DRI2rendererQueryExtension *rendererQuery;const __DRI2interopExtension *interop;const __DRIconfigOptionsExtension *configOptions;const __DRImutableRenderBufferDriverExtension *mutable_render_buffer; ...
}
三. dri2_create_screen的实现
万里长征刚开始，到这里还只是第一步啊，得接续往下走，我们接着接续分析！
//src/egl/drivers/dri2/egl_dri2.c
dri2_create_screen(...)dri2_dpy->dri_screen = dri2_dpy->image_driver->createNewScreen2(....)
这里的dri2_dpy->image_driver指向那里呢，这里可以在章节2.1和章节2.2找到答案，它指向了dri_util.c里面的结构体driImageDriverExtension，如下:
//src/gallium/frontends/dri/dri_util.c
/** Image driver interface */
const __DRIimageDriverExtension driImageDriverExtension = {.base = { __DRI_IMAGE_DRIVER, 1 },.createNewScreen2 = driCreateNewScreen2,.createNewDrawable = driCreateNewDrawable,.getAPIMask = driGetAPIMask,.createContextAttribs = driCreateContextAttribs,
};
所以我们继续看driCreateNewScreen2的实现:
//src/gallium/frontends/dri/dri_util.c
driCreateNewScreen2(...)__DRIscreen *psppsp = calloc(1, sizeof(*psp))psp->driver =((__DRIDriverVtableExtension *)driver_extensions[i])->vtable;//指向galliumdrm_driver_apipsp->driver->InitScreen(psp)//这里会指向galliumdrm_driver_api中dri2_init_screen，在dri2.c中实现
我们接着来看dri2_init_screen的实现:
//src/gallium/frontends/dri/dri2.c
static const __DRIconfig **
dri2_init_screen(__DRIscreen * sPriv)
{const __DRIconfig **configs;struct dri_screen *screen;//各种screen开始出现struct pipe_screen *pscreen = NULL;screen = CALLOC_STRUCT(dri_screen);//构建一个，还没有开始初始化screen->sPriv = sPriv;//开始指向，并赋值了screen->fd = sPriv->fd;sPriv->driverPrivate = (void *)screen;//相互引用if (pipe_loader_drm_probe_fd(&screen->dev, screen->fd)) {//详见章节3.1pscreen = pipe_loader_create_screen(screen->dev);//详见章节3.2dri_init_options(screen);}dri2_init_screen_extensions(screen, pscreen, false);configs = dri_init_screen_helper(screen, pscreen);...
}
为了排版简介明了一些，这里我们不全部放在一个大章节里面，而是进行小章节，这样排版会更加合理看起来也更加的舒服！
3.1 pipe_loader_drm_probe_fd
我们接着继续往下分析该源码的实现:
//src/gallium/auxiliary/pipe-loader/pipe_loader_drm.cstatic struct pipe_screen *
pipe_loader_drm_create_screen(struct pipe_loader_device *dev,const struct pipe_screen_config *config, bool sw_vk)
{struct pipe_loader_drm_device *ddev = pipe_loader_drm_device(dev);return ddev->dd->create_screen(ddev->fd, config);
}static const struct pipe_loader_ops pipe_loader_drm_ops = {.create_screen = pipe_loader_drm_create_screen,.get_driconf = pipe_loader_drm_get_driconf,.release = pipe_loader_drm_release
};pipe_loader_drm_probe_fd(...)pipe_loader_drm_probe_fd_nodup(struct pipe_loader_device **dev, int fd)struct pipe_loader_drm_device *ddev = CALLOC_STRUCT(pipe_loader_drm_device);ddev->base.ops = &pipe_loader_drm_ops;ddev->fd = fd;ddev->base.driver_name = loader_get_driver_for_fd(fd)ddev->dd = get_driver_descriptor(ddev->base.driver_name, plib)*dev = &ddev->base;
我们接着看get_driver_descriptor的实现，看看它究竟在干啥！
//src/gallium/auxiliary/pipe-loader/pipe_loader_drm.c
#ifdef GALLIUM_STATIC_TARGETS
static const struct drm_driver_descriptor *driver_descriptors[] = {&i915_driver_descriptor,&iris_driver_descriptor,&crocus_driver_descriptor,&nouveau_driver_descriptor,&r300_driver_descriptor,&r600_driver_descriptor,&radeonsi_driver_descriptor,&vmwgfx_driver_descriptor,&kgsl_driver_descriptor,&msm_driver_descriptor,&virtio_gpu_driver_descriptor,&v3d_driver_descriptor,&vc4_driver_descriptor,&panfrost_driver_descriptor,&asahi_driver_descriptor,&etnaviv_driver_descriptor,&tegra_driver_descriptor,&lima_driver_descriptor,&zink_driver_descriptor,&xxx_gpu_driver_descriptor,
};
#endifstatic const struct drm_driver_descriptor *
get_driver_descriptor(const char *driver_name, struct util_dl_library **plib)
{
#ifdef GALLIUM_STATIC_TARGETSfor (int i = 0; i < ARRAY_SIZE(driver_descriptors); i++) {if (strcmp(driver_descriptors[i]->driver_name, driver_name) == 0)return driver_descriptors[i];}return &kmsro_driver_descriptor;
#else...
#endif...
}
那么这里的xxx_driver_descriptor是怎么实现的，刚开始我通过grep搜索发现只有定义，没有怎么实现。尼玛见鬼了不成，这又是套路啊，又是通过各种宏来实现的。我们看看它是怎么实现的(这里我以景嘉微的xxx_gpu为例来说明)。
//src/gallium/auxiliary/target-helpers/drm_helper.h/*** Instantiate a drm_driver_descriptor struct.*/
#define DEFINE_DRM_DRIVER_DESCRIPTOR(descriptor_name, driver, _driconf, _driconf_count, func) \
const struct drm_driver_descriptor descriptor_name = { \.driver_name = #driver, \.driconf = _driconf, \.driconf_count = _driconf_count, \.create_screen = func, \
};#define DRM_DRIVER_DESCRIPTOR(driver, driconf, driconf_count) \DEFINE_DRM_DRIVER_DESCRIPTOR(driver##_driver_descriptor, driver, driconf, driconf_count, pipe_##driver##_create_screen)#include "xxx_gpu/drm/xxx_gpu_drm_public.h"static struct pipe_screen *
pipe_xxx_gpu_create_screen(int fd, const struct pipe_screen_config *config)
{struct pipe_screen *screen;screen = xxx_gpu_drm_create_screen(fd);return screen ? debug_screen_wrap(screen) : NULL;
}DRM_DRIVER_DESCRIPTOR(xxx_gpu, NULL, 0)
所以分析到这里我们获得了ddev->dd的指向，它指向了vendor实现的结构体drm_driver_descriptor。搞清楚了这个我们接着继续看 ddev->dd->create_screen的实现，它指向了pipe_xxx_gpu_create_screen，我们接着分析:
//src/gallium/auxiliary/target-helpers/drm_helper.h
static struct pipe_screen *
pipe_xxx_gpu_create_screen(int fd, const struct pipe_screen_config *config)
{struct pipe_screen *screen;screen = xxx_gpu_drm_create_screen(fd);//返回封装好的pipe_screenstruct xxx_gpu_winsys *ws;ws = CALLOC_STRUCT(xxx_gpu_winsys)ws->screen = xxx_gpu_create_screen(ws)return ws->screenreturn screen ? debug_screen_wrap(screen) : NULL;
}3.2 pipe_loader_create_screen
分析完了pipe_loader_drm_probe_fd流程，我们接着咔咔一顿接着继续分析，pipe_loader_create_screen它会构建pipe_screen的结构体类型！
pipe_loader_create_screen(...)//src/gallium/frontends/dri/dri2.cpipe_loader_create_screen(...)//src/gallium/auxiliary/pipe-loader/pipe_loader.cpipe_loader_create_screen_vk(...)dev->ops->create_screen(...)//这里的ops指向了pipe_loader_drm_ops，定义在pipe_loader_drm.c pipe_loader_drm_create_screen(...)ddev->dd->create_screen(...)//这里的ddev->dd指向了前面获取的结构体pipe_xxx_gpu_create_screen(...)
到这里整个流程就基本结束了。后续如果需要查看的，可以继续dri2_init_screen研究，主要是要理清楚几个screen之间的关系！
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