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finish the doc authored by Vincent Wei's avatar Vincent Wei
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Writing-DRI-Engine-Driver-for-Your-GPU.md
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......@@ -50,7 +50,7 @@ There are two configure options related to the `dri` engine:
available on Linux, and you need to install the `libdrm` 2.4 or later
first.
* `--with-targetname=external`. When you configure MiniGUI with this
option. MiniGUI will use the external function `__dri_ex_driver_get`
option, MiniGUI will use the external function `__dri_ex_driver_get`
to initialize the DRI driver. If you do not implement this function,
the link will fail.
......@@ -67,23 +67,198 @@ pixelformat=XR24
device=/dev/dri/card0
```
You can use the key `dri.device` to specify your DRI device.
Note that the `defaultmode` and `dpi` keys are standard keys for
a NEWGAL engine. These two keys define the screen resolution for
MiniGUI.
You can use the key `dri.pixelformat` to specify the DRM pixel format for the
screen. We use DRM fourcc code to defined the pixel format of the screen
surface. For more information, please see `<drm/drm_fourcc.h>` header file.
Note that only 8/16/24/32 bpp RGB formats are supported. For example, `XR24`
means `X8R8G8B8` pixel format.
For `dri` engine, you can use the key `dri.device` to specify
your DRI device. Generally, it is `/dev/dri/card0`.
You can use the key `dri.pixelformat` to specify the DRM pixel format
of the screen. We use libdrm's fourcc code to defined the pixel format
of the screen surface in MiniGUI run-time configuration. For example,
`XR24` means `X8R8G8B8` pixel format, and `AR32` means `A8R8G8B8` pixel
format.
For more information, please see `<drm/drm_fourcc.h>` header file.
Note that only 8/16/24/32 bpp RGB formats are supported.
### Implement DRI driver
The header file `<minigui/exstubs.h>` defines the operators (a set of
callback functions) you need to implement for your GPU externally.
The header file `<minigui/exstubs.h>` defines the external sutbs and
the driver operators (a set of callback functions) you need to implement
for your GPU externally.
First, you need to implement the following external stub:
DriDriverOps* __dri_ex_driver_get (const char* driver_name);
This function takes an argument `driver_name` and returns NULL or
a valid pointer of `DriDriverOps` to MiniGUI. The argument `driver_name`
gives the driver name determined by libdrm. Generally, it is the model
or number of your GPU. For example, for Intel i915 GPU, the driver name
will be `i915`. The `__dri_ex_driver_get` can returns different
`DriDriverOps` to MiniGUI according to the driver name. In this way,
your implementation can support multiple GPUs.
If the external stub returns NULL, MiniGUI will use the dumb frame buffer
instead.
The `DriDriverOps` is a struct type consisted by a set of operators
(callbacks):
/**
* The struct type defines the operators for a DRI driver.
*/
typedef struct _DriDriverOps {
/**
* This operator creates the DriDriver object.
*
* \note The driver must implement this operator.
*/
DriDriver* (*create_driver) (int device_fd);
/**
* This operator destroies the DriDriver object.
*
* \note The driver must implement this operator.
*/
void (*destroy_driver) (DriDriver *driver);
/**
* This operator flushs the batch buffer of the driver or the hardware cache.
*
* \note This operator can be NULL.
*/
void (* flush_driver) (DriDriver *driver);
/**
* This operator creates a buffer with the specified pixel format,
* width, and height. If succeed, a valid (not zero) buffer identifier
* and the picth (row stride in bytes) will be returned.
* If failed, it returns 0.
*
* \note The driver must implement this operator.
*/
uint32_t (* create_buffer) (DriDriver *driver,
uint32_t drm_format,
unsigned int width, unsigned int height,
unsigned int *pitch);
BOOL (* fetch_buffer) (DriDriver *driver,
uint32_t buffer_id,
unsigned int *width, unsigned int *height,
unsigned int *pitch);
/**
* This operator maps the buffer into the current process's virtual memory
* space, and returns the virtual address. If failed, it returns NULL.
*
* \note The driver must implement this operator.
*/
DriSurfaceBuffer* (* map_buffer) (DriDriver *driver,
uint32_t buffer_id);
/**
* This operator un-maps a buffer.
*
* \note The driver must implement this operator.
*/
void (* unmap_buffer) (DriDriver *driver, DriSurfaceBuffer* buffer);
/**
* This operator destroies a buffer.
*
* \note The driver must implement this operator.
*/
void (* destroy_buffer) (DriDriver *driver, uint32_t buffer_id);
/**
* This operator clears the specific rectangle area of a buffer
* with the specific pixel value. If succeed, it returns 0.
*
* \note If this operator is set as NULL, the driver does not support
* hardware accelerated clear operation.
*/
int (* clear_buffer) (DriDriver *driver,
DriSurfaceBuffer* dst_buf, const GAL_Rect* rc, uint32_t pixel_value);
/**
* This operator checks whether a hardware accelerated blit
* can be done between the source buffer and the destination buffer.
* If succeed, it returns 0.
*
* \note If this operator is set as NULL, it will be supposed that
* the driver does not support any hardware accelerated blit operation.
*/
int (* check_blit) (DriDriver *driver,
DriSurfaceBuffer* src_buf, DriSurfaceBuffer* dst_buf);
/**
* This operator copies bits from a source buffer to a destination buffer.
*
* \note If this operator is set as NULL, the driver does not support
* hardware accelerated copy blit.
*/
int (* copy_blit) (DriDriver *driver,
DriSurfaceBuffer* src_buf, const GAL_Rect* src_rc,
DriSurfaceBuffer* dst_buf, const GAL_Rect* dst_rc,
enum DriColorLogicOp logic_op);
/**
* This operator blits pixles from a source buffer with the source alpha value
* specified to a destination buffer.
*
* \note If this operator is set as NULL, the driver does not support
* hardware accelerated blit with alpha.
*/
int (* alpha_blit) (DriDriver *driver,
DriSurfaceBuffer* src_buf, const GAL_Rect* src_rc,
DriSurfaceBuffer* dst_buf, const GAL_Rect* dst_rc, uint8_t alpha);
/**
* This operator blits pixles from a source buffer to a destination buffer,
* but skipping the pixel value specified by \a color_key.
*
* \note If this operator is set as NULL, the driver does not support
* hardware accelerated blit with color key.
*/
int (* key_blit) (DriDriver *driver,
DriSurfaceBuffer* src_buf, const GAL_Rect* src_rc,
DriSurfaceBuffer* dst_buf, const GAL_Rect* dst_rc, uint32_t color_key);
/**
* This operator blits pixles from a source buffer with the source alpha value
* specified to a destination buffer, but skipping the pixel value specified.
*
* \note If this operator is set as NULL, the driver does not support
* hardware accelerated blit with alpha and color key.
*/
int (* alpha_key_blit) (DriDriver *driver,
DriSurfaceBuffer* src_buf, const GAL_Rect* src_rc,
DriSurfaceBuffer* dst_buf, const GAL_Rect* dst_rc,
uint8_t alpha, uint32_t color_key);
} DriDriverOps;
If the external stub `__dri_ex_driver_get` returns a valid pointer
of `DriDriverOps`, MiniGUI will call the operator `create_driver`
to initialize the DRI driver. The operator will return a pointer
to the type of `DriDriver`. All other operators of `DriDriverOps`
need this pointer as the context of your DRI driver.
Note that MiniGUI does not defined the detailed structure of
`DriDriver`, it is up to your implementation:
/**
* The struct type represents the DRI sub driver.
* The concrete struct should be defined by the driver.
*/
struct _DriDriver;
typedef struct _DriDriver DriDriver;
For other operators, please see the comments above.
To exploit the GPU's accelerated rendering capabilities, a MiniGUI app
can use `cairo` and/or `OpenGL ES` to assist in rendering 2D/3D graphics
when using the `dri` engine. We will provide some samples in `mg-tests`
or `mg-samples` for this purpose.
### Restrictions
......@@ -98,8 +273,19 @@ need this privilege when you use the future `dri` engine.
## Example
As an example, we implement the sub driver for `i915` graphics chard
As an example, we implement the DRI driver for `i915` graphics chard
in `mg-tests/dri-engine/`. Please refer to `mg-tests` repository:
https://github.com/VincentWei/mg-tests/tree/master/dri-engine
## Future Features
In the near future, the MiniGUI team will:
* Enhance `dri` engine to support MiniGUI-Processes run-time mode.
* Implement the MiniGUI back-end of `cairo` and MiniGUI EGL for OpenGL,
OpenGL ES, and OpenVG, in order to fully exploit the GPU's 2D/3D
accelerated rendering capabilities.
We will provide some samples in `mg-tests` or `mg-samples` for this purpose.