Android环境下Mesa初始化流程重学习之eglCreateContext

Mesa初始化流程重学习之eglCreateContext

引言

没有啥好说的了，直接上手撸代码！总得找点事情干不是!我打工我快乐！我奋斗，我快乐！

一. 核心结构体之间的关联

在这里插入图片描述

二. eglCreateContext流程分析

eglCreateContext(...)//src/egl/main/eglapi.c
    _EGLContext *context;
        context = disp->Driver->CreateContext(disp, conf, share, attrib_list)//这里的Driver指向_eglDriver，定义在egl_dri2.c中
            dri2_create_context(...)//Called via eglCreateContext(), drv->CreateContext()
                struct dri2_egl_context *dri2_ctx；
                dri2_ctx = malloc(sizeof *dri2_ctx)
                dri2_ctx->dri_context = dri2_dpy->image_driver->createContextAttribs(...)//image_driver指向driImageDriverExtension，实现在dri_util.c中，指向driCreateContextAttribs
                return &dri2_ctx->base;
                
 
                
driCreateContextAttribs(...) //src/gallium/frontends/dri/dri_util.c
    __DRIcontext *context;
    context = calloc(1, sizeof *context);
    context->driScreenPriv = screen;//__DRIscreen *screen
    dri_create_context(...)//src/gallium/frontends/dri/dri_context.c
           __DRIscreen *sPriv = cPriv->driScreenPriv;
            struct dri_screen *screen = dri_screen(sPriv);
            struct dri_context *ctx = NULL;        
            ctx = CALLOC_STRUCT(dri_context);    
            cPriv->driverPrivate = ctx;//这个关系，后面必须通过关系图画出来
            ctx->cPriv = cPriv;
            ctx->sPriv = sPriv;
            ctx->st = st_api_create_context(&screen->base, &attribs, &ctx_err,
				   st_share);
            ctx->st->st_manager_private = (void *) ctx;
            
            
st_api_create_context(...) //src/mesa/state_tracker/st_manager.c
   struct st_context *st;
   struct pipe_context *pipe;
   pipe = smapi->screen->context_create(smapi->screen, NULL, ctx_flags);//详见章节2.1
   st = st_create_context(api, pipe, mode_ptr, shared_ctx,
                          &attribs->options, no_error,
                          !!smapi->validate_egl_image);//详见章节2.2
   return &st->iface;

2.1 smapi->screen->context_create的实现

这块我们在前面分析时，已经提到过了。在vendor里面会进行赋值,如下:

struct pipe_screen *
xxx_gpu_create_screen(struct xxx_gpu_winsys *winsys)
{
   struct xxx_gpu_screen *screen = CALLOC_STRUCT(xxx_gpu_screen);

   if (!screen)
      return NULL;

   screen->ws = winsys;

   screen->base.get_name             = xxx_gpu_get_name;
   screen->base.get_vendor           = xxx_gpu_get_vendor;
   screen->base.get_device_vendor    = xxx_gpu_get_device_vendor;

   screen->base.get_param            = xxx_gpu_get_param;
   screen->base.get_paramf           = xxx_gpu_get_paramf;
   screen->base.get_shader_param     = xxx_gpu_get_shader_param;
   screen->base.get_compute_param    = xxx_gpu_get_compute_param;
   screen->base.get_compiler_options = xxx_gpu_get_compiler_options;
   screen->base.is_format_supported  = xxx_gpu_is_format_supported;

   screen->base.get_timestamp   = xxx_gpu_get_timestamp;

   screen->base.context_create  = xxx_gpu_context_create;
   screen->base.destroy         = xxx_gpu_destroy_screen;

   screen->base.fence_reference = xxx_gpu_fence_reference;
   screen->base.fence_finish    = xxx_gpu_fence_finish;
   screen->base.fence_get_fd    = xxx_gpu_fence_get_fd;

   xxx_gpu_screen_resource_init(&screen->base);

   slab_create_parent(&screen->transfer_pool, sizeof(struct xxx_gpu_transfer), 16);

   glsl_type_singleton_init_or_ref();

   return &screen->base;
}

2.2 st_create_context的实现

接着继续往下看:

xxx_gpu_create_screen(...)//src/gallium/drivers/xxx_gpu/xxx_gpu_screen.c
    screen->base.context_create  = xxx_gpu_context_create;

xxx_gpu_context_create(...)//src/gallium/drivers/xxx_gpu/xxx_gpu_context.c
   struct xxx_gpu_screen *screen = xxx_gpu_screen(pscreen);
   struct xxx_gpu_context *ctx = CALLOC_STRUCT(xxx_gpu_context);
   ctx->base.screen = pscreen;
   ctx->base.priv = priv;

   ctx->ws = screen->ws;
   ...
   ctx->base.flush = xxx_gpu_flush;
   ...

我们接着继续分析_mesa_initialize_context

_mesa_initialize_context

_mesa_initialize_context(...)//src/mesa/main/context.c
    ctx->Driver = *driverFunctions;
    /* setup the API dispatch tables with all nop functions */
    ctx->OutsideBeginEnd = _mesa_alloc_dispatch_table(false);
        _mesa_alloc_dispatch_table(...)//src/mesa/main/context.c
            struct _glapi_table *table = _mesa_new_nop_table(numEntries, glthread)//和gl_dispatch分发有关
                    struct _glapi_table *
                    _mesa_new_nop_table(unsigned numEntries, bool glthread)
                    {
                        struct _glapi_table *table;
                        table = _glapi_new_nop_table(numEntries);
                        return table;
                    }            
            return table;
            
            
 _glapi_table *_glapi_new_nop_table(...)//src/mapi/mapi_glapi.c
    struct _glapi_table *table;
    table = malloc(num_entries * sizeof(mapi_func));
    memcpy(table, table_noop_array, num_entries * sizeof(mapi_func));
    return table
            

//build-android-aarch64/src/mapi/shared-glapi/glapi_mapi_tmp.h   
static void APIENTRY noopFlush(void)
{
      noop_warn("glFlush");
}
const mapi_func table_noop_array[] = {
    ...
    (mapi_func) noopFlush,
    ...
}

我们接着继续分析st_create_context_priv

st_create_context_priv

st_create_context_priv(...)//src/mesa/state_tracker/st_context.c
   struct pipe_screen *screen = pipe->screen;
   struct st_context *st = CALLOC_STRUCT( st_context);    
   ctx->st = st;
   st->ctx = ctx;
   st->screen = screen;
   st->pipe = pipe;   
   _mesa_initialize_dispatch_tables(ctx);
   
 
 _mesa_initialize_dispatch_tables(...) //src/mesa/main/context.c
    _mesa_init_dispatch(ctx)//build-android-aarch64/src/mapi/glapi/gen/api_exec_init.cZ这个是构建完成以后生成的
    struct _glapi_table *table = ctx->OutsideBeginEnd;//还记得这个地方是怎么被赋值的吗
    SET_Flush(table, _mesa_Flush);//我们以这个实现来进行举例说明
    
// build-android-arm/src/mesa/main/dispatch.h   
#define SET_Flush(disp, func) do { \
   void (GLAPIENTRYP fn)(void) = func; \
   SET_by_offset(disp, _gloffset_Flush, fn); \
} while (0)  


#define SET_by_offset(disp, offset, fn) \
    do { \
        if ( (offset) < 0 ) { \
            /* fprintf( stderr, "[%s:%u] SET_by_offset(%p, %d, %s)!\n", */ \
            /*         __func__, __LINE__, disp, offset, # fn); */ \
            /* abort(); */ \
        } \
        else { \
            ( (_glapi_proc *) (disp) )[offset] = (_glapi_proc) fn; \
        } \
    } while(0)