• Android12之DRM基本接口实现(二)

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    1.前言

    本篇目的：探究DRM基本接口的实现，底层实现到底是如何与DRM驱动通信的？

    2.DRM基本接口实现解析

    <1>.DRM之drmModeGetResources获取CRTC和Connector的id号

    drm_public drmModeResPtr drmModeGetResources(int fd)
{
	struct drm_mode_card_res res, counts;
	drmModeResPtr r = 0;

retry:
	memclear(res);
	if (drmIoctl(fd, DRM_IOCTL_MODE_GETRESOURCES, &res))
		return 0;

	counts = res;

	if (res.count_fbs) {
		res.fb_id_ptr = VOID2U64(drmMalloc(res.count_fbs*sizeof(uint32_t)));
		if (!res.fb_id_ptr)
			goto err_allocs;
	}
	if (res.count_crtcs) {
		res.crtc_id_ptr = VOID2U64(drmMalloc(res.count_crtcs*sizeof(uint32_t)));
		if (!res.crtc_id_ptr)
			goto err_allocs;
	}
	if (res.count_connectors) {
		res.connector_id_ptr = VOID2U64(drmMalloc(res.count_connectors*sizeof(uint32_t)));
		if (!res.connector_id_ptr)
			goto err_allocs;
	}
	if (res.count_encoders) {
		res.encoder_id_ptr = VOID2U64(drmMalloc(res.count_encoders*sizeof(uint32_t)));
		if (!res.encoder_id_ptr)
			goto err_allocs;
	}

	if (drmIoctl(fd, DRM_IOCTL_MODE_GETRESOURCES, &res))
		goto err_allocs;

	/* The number of available connectors and etc may have changed with a
	 * hotplug event in between the ioctls, in which case the field is
	 * silently ignored by the kernel.
	 */
	if (counts.count_fbs < res.count_fbs ||
	    counts.count_crtcs < res.count_crtcs ||
	    counts.count_connectors < res.count_connectors ||
	    counts.count_encoders < res.count_encoders)
	{
		drmFree(U642VOID(res.fb_id_ptr));
		drmFree(U642VOID(res.crtc_id_ptr));
		drmFree(U642VOID(res.connector_id_ptr));
		drmFree(U642VOID(res.encoder_id_ptr));

		goto retry;
	}

	/*
	 * return
	 */
	if (!(r = drmMalloc(sizeof(*r))))
		goto err_allocs;

	r->min_width     = res.min_width;
	r->max_width     = res.max_width;
	r->min_height    = res.min_height;
	r->max_height    = res.max_height;
	r->count_fbs     = res.count_fbs;
	r->count_crtcs   = res.count_crtcs;
	r->count_connectors = res.count_connectors;
	r->count_encoders = res.count_encoders;

	r->fbs        = drmAllocCpy(U642VOID(res.fb_id_ptr), res.count_fbs, sizeof(uint32_t));
	r->crtcs      = drmAllocCpy(U642VOID(res.crtc_id_ptr), res.count_crtcs, sizeof(uint32_t));
	r->connectors = drmAllocCpy(U642VOID(res.connector_id_ptr), res.count_connectors, sizeof(uint32_t));
	r->encoders   = drmAllocCpy(U642VOID(res.encoder_id_ptr), res.count_encoders, sizeof(uint32_t));
	if ((res.count_fbs && !r->fbs) ||
	    (res.count_crtcs && !r->crtcs) ||
	    (res.count_connectors && !r->connectors) ||
	    (res.count_encoders && !r->encoders))
	{
		drmFree(r->fbs);
		drmFree(r->crtcs);
		drmFree(r->connectors);
		drmFree(r->encoders);
		drmFree(r);
		r = 0;
	}

err_allocs:
	drmFree(U642VOID(res.fb_id_ptr));
	drmFree(U642VOID(res.crtc_id_ptr));
	drmFree(U642VOID(res.connector_id_ptr));
	drmFree(U642VOID(res.encoder_id_ptr));

	return r;
}


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    核心要点1

    1.调用drmIoctl(fd, DRM_IOCTL_MODE_GETRESOURCES, &res)获取CRTC和Connector的id号。

    2.drm_mode_card_res数据结构

    struct drm_mode_card_res {
  __u64 fb_id_ptr;
  __u64 crtc_id_ptr;
  __u64 connector_id_ptr;
  __u64 encoder_id_ptr;
  __u32 count_fbs;
  __u32 count_crtcs;
  __u32 count_connectors;
  __u32 count_encoders;
  __u32 min_width;
  __u32 max_width;
  __u32 min_height;
  __u32 max_height;
};


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    <2>.DRM之drmModeGetConnector连接Connector显示器

    static drmModeConnectorPtr
_drmModeGetConnector(int fd, uint32_t connector_id, int probe)
{
	struct drm_mode_get_connector conn, counts;
	drmModeConnectorPtr r = NULL;
	struct drm_mode_modeinfo stack_mode;

	memclear(conn);
	conn.connector_id = connector_id;
	if (!probe) {
		conn.count_modes = 1;
		conn.modes_ptr = VOID2U64(&stack_mode);
	}

	if (drmIoctl(fd, DRM_IOCTL_MODE_GETCONNECTOR, &conn))
		return 0;

retry:
	counts = conn;

	if (conn.count_props) {
		conn.props_ptr = VOID2U64(drmMalloc(conn.count_props*sizeof(uint32_t)));
		if (!conn.props_ptr)
			goto err_allocs;
		conn.prop_values_ptr = VOID2U64(drmMalloc(conn.count_props*sizeof(uint64_t)));
		if (!conn.prop_values_ptr)
			goto err_allocs;
	}

	if (conn.count_modes) {
		conn.modes_ptr = VOID2U64(drmMalloc(conn.count_modes*sizeof(struct drm_mode_modeinfo)));
		if (!conn.modes_ptr)
			goto err_allocs;
	} else {
		conn.count_modes = 1;
		conn.modes_ptr = VOID2U64(&stack_mode);
	}

	if (conn.count_encoders) {
		conn.encoders_ptr = VOID2U64(drmMalloc(conn.count_encoders*sizeof(uint32_t)));
		if (!conn.encoders_ptr)
			goto err_allocs;
	}

	if (drmIoctl(fd, DRM_IOCTL_MODE_GETCONNECTOR, &conn))
		goto err_allocs;

	/* The number of available connectors and etc may have changed with a
	 * hotplug event in between the ioctls, in which case the field is
	 * silently ignored by the kernel.
	 */
	if (counts.count_props < conn.count_props ||
	    counts.count_modes < conn.count_modes ||
	    counts.count_encoders < conn.count_encoders) {
		drmFree(U642VOID(conn.props_ptr));
		drmFree(U642VOID(conn.prop_values_ptr));
		if (U642VOID(conn.modes_ptr) != &stack_mode)
			drmFree(U642VOID(conn.modes_ptr));
		drmFree(U642VOID(conn.encoders_ptr));

		goto retry;
	}

	if(!(r = drmMalloc(sizeof(*r)))) {
		goto err_allocs;
	}

	r->connector_id = conn.connector_id;
	r->encoder_id = conn.encoder_id;
	r->connection   = conn.connection;
	r->mmWidth      = conn.mm_width;
	r->mmHeight     = conn.mm_height;
	/* convert subpixel from kernel to userspace */
	r->subpixel     = conn.subpixel + 1;
	r->count_modes  = conn.count_modes;
	r->count_props  = conn.count_props;
	r->props        = drmAllocCpy(U642VOID(conn.props_ptr), conn.count_props, sizeof(uint32_t));
	r->prop_values  = drmAllocCpy(U642VOID(conn.prop_values_ptr), conn.count_props, sizeof(uint64_t));
	r->modes        = drmAllocCpy(U642VOID(conn.modes_ptr), conn.count_modes, sizeof(struct drm_mode_modeinfo));
	r->count_encoders = conn.count_encoders;
	r->encoders     = drmAllocCpy(U642VOID(conn.encoders_ptr), conn.count_encoders, sizeof(uint32_t));
	r->connector_type  = conn.connector_type;
	r->connector_type_id = conn.connector_type_id;

	if ((r->count_props && !r->props) ||
	    (r->count_props && !r->prop_values) ||
	    (r->count_modes && !r->modes) ||
	    (r->count_encoders && !r->encoders)) {
		drmFree(r->props);
		drmFree(r->prop_values);
		drmFree(r->modes);
		drmFree(r->encoders);
		drmFree(r);
		r = 0;
	}

err_allocs:
	drmFree(U642VOID(conn.prop_values_ptr));
	drmFree(U642VOID(conn.props_ptr));
	if (U642VOID(conn.modes_ptr) != &stack_mode)
		drmFree(U642VOID(conn.modes_ptr));
	drmFree(U642VOID(conn.encoders_ptr));

	return r;
}


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    核心要点2

    1.drmIoctl(fd, DRM_IOCTL_MODE_GETCONNECTOR, &conn)：连接CONNECTOR到显示器

    2.drm_mode_get_connector数据结构

    struct drm_mode_get_connector {
  __u64 encoders_ptr;
  __u64 modes_ptr;
  __u64 props_ptr;
  __u64 prop_values_ptr;
  __u32 count_modes;
  __u32 count_props;
  __u32 count_encoders;
  __u32 encoder_id;
  __u32 connector_id;
  __u32 connector_type;
  __u32 connector_type_id;
  __u32 connection;
  __u32 mm_width;
  __u32 mm_height;
  __u32 subpixel;
  __u32 pad;
};


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    <3>.DRM之modeset_create_fb添加framebuffer设备

    static int modeset_create_fb(int fd, struct buffer_object *bo) {
  struct drm_mode_create_dumb create = {};
  struct drm_mode_map_dumb map = {};

  create.width = bo->width;
  create.height = bo->height;
  create.bpp = 32;
  drmIoctl(fd, DRM_IOCTL_MODE_CREATE_DUMB, &create);
  printf("create dumb w %d h %d\n", bo->width, bo->height);
  getchar();

  bo->pitch = create.pitch;
  bo->size = create.size;
  bo->handle = create.handle;
  drmModeAddFB(fd, bo->width, bo->height, 24, 32, bo->pitch, bo->handle,
               &bo->fb_id);
  printf("drmModeAddFB\n");
  getchar();

  map.handle = create.handle;
  drmIoctl(fd, DRM_IOCTL_MODE_MAP_DUMB, &map);
  printf("map dumb\n");
  getchar();
  bo->vaddr = static_cast<unsigned char *>(mmap64(
      0, create.size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, map.offset));
  memset(bo->vaddr, 0xff, bo->size);
  return 0;
}


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    核心要点3

    1.drmIoctl(fd, DRM_IOCTL_MODE_CREATE_DUMB, &create)： 增加申请DUMB共享内存
    2.drmModeAddFB(fd, bo->width, bo->height, 24, 32, bo->pitch, bo->handle,&bo->fb_id);
    DRM_IOCTL(fd, DRM_IOCTL_MODE_ADDFB, &f);：添加一个FrameBuffer
    3.bo->vaddr = static_cast(mmap64( 0, create.size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, map.offset));：映射DRM图形buffer的共享内存到bo->vaddr地址。
    memset(bo->vaddr, 0xff, bo->size);：设置白色。
    4.drm_mode_create_dumb和drm_mode_map_dumb数据结构

    struct drm_mode_create_dumb {
  __u32 height;
  __u32 width;
  __u32 bpp;
  __u32 flags;
  __u32 handle;
  __u32 pitch;
  __u64 size;
};

struct drm_mode_map_dumb {
  __u32 handle;
  __u32 pad;
  __u64 offset;
};


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    <4>.DRM之drmModeSetCrtcCRTC开始扫描framebuffer数据显示

    drm_public int drmModeSetCrtc(int fd, uint32_t crtcId, uint32_t bufferId,
		   uint32_t x, uint32_t y, uint32_t *connectors, int count,
		   drmModeModeInfoPtr mode)
{
	struct drm_mode_crtc crtc;

	memclear(crtc);
	crtc.x             = x;
	crtc.y             = y;
	crtc.crtc_id       = crtcId;
	crtc.fb_id         = bufferId;
	crtc.set_connectors_ptr = VOID2U64(connectors);
	crtc.count_connectors = count;
	if (mode) {
	  memcpy(&crtc.mode, mode, sizeof(struct drm_mode_modeinfo));
	  crtc.mode_valid = 1;
	}

	return DRM_IOCTL(fd, DRM_IOCTL_MODE_SETCRTC, &crtc);
}


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    核心要点4

    1.DRM_IOCTL(fd, DRM_IOCTL_MODE_SETCRTC, &crtc)：CRTC对framebuffer的数据进行扫描

    2.drm_mode_crtc数据结构

    struct drm_mode_crtc {
  __u64 set_connectors_ptr;
  __u32 count_connectors;
  __u32 crtc_id;
  __u32 fb_id;
  __u32 x;
  __u32 y;
  __u32 gamma_size;
  __u32 mode_valid;
  struct drm_mode_modeinfo mode;
};



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    <5>.DRM之modeset_destroy_fb关闭framebuffer设备

    static void modeset_destroy_fb(int fd, struct buffer_object *bo) {
  struct drm_mode_destroy_dumb destroy = {};

  drmModeRmFB(fd, bo->fb_id);
  munmap(bo->vaddr, bo->size);
  destroy.handle = bo->handle;
  drmIoctl(fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroy);
}


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    核心要点5

    1.drmIoctl(fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroy);：销毁DUMB共享内存

    2.drm_mode_destroy_dumb数据结构

    struct drm_mode_destroy_dumb {
  __u32 handle;
};



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    <6>.DRM之drmModeFreeConnector断开Connector连接

    drm_public void drmModeFreeConnector(drmModeConnectorPtr ptr)
{
	if (!ptr)
		return;

	drmFree(ptr->encoders);
	drmFree(ptr->prop_values);
	drmFree(ptr->props);
	drmFree(ptr->modes);
	drmFree(ptr);
}


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    核心要点6

    1.调用drmFree释放内存，内部调用free()函数。

    2.drmFree函数实现

    drm_public void drmFree(void *pt)
{
    free(pt);
}



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    <7>.DRM之drmModeFreeResources释放资源

    drm_public void drmModeFreeResources(drmModeResPtr ptr)
{
	if (!ptr)
		return;

	drmFree(ptr->fbs);
	drmFree(ptr->crtcs);
	drmFree(ptr->connectors);
	drmFree(ptr->encoders);
	drmFree(ptr);
}


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    核心要点7

    1.调用drmFree释放资源，本质和drmModeFreeConnector一样，也是释放内存资源。

    3.DRM基本接口总结

    • 1.drmModeGetResources函数调用DRM驱动通过ioctl(DRM_IOCTL_MODE_GETRESOURCES)：获取CRTC和Connector的id号。
    • 2.drmModeGetConnector函数调用ioctl(DRM_IOCTL_MODE_GETCONNECTOR)：连接CONNECTOR到显示器
    • 3.modeset_create_fb函数调用ioctl(DRM_IOCTL_MODE_ADDFB)：添加一个FrameBuffer
    • 4.drmModeSetCrtc函数调用ioctl(DRM_IOCTL_MODE_SETCRTC)：CRTC对framebuffer的数据进行扫描
    • 5.modeset_destroy_fb函数调用ioctl(DRM_IOCTL_MODE_DESTROY_DUMB)：销毁DUMB共享内存
    • 6.drmModeFreeConnector函数调用drmFree释放内存资源
    • 7.drmModeFreeResources函数调用drmFree释放内存资源
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  • 原文地址：https://blog.csdn.net/u010164190/article/details/133902475