[Mesa-dev] [PATCH 2/3] egl_dri2: add support for Android
Chia-I Wu
olvaffe at gmail.com
Thu Aug 25 23:05:38 PDT 2011
On Fri, Aug 26, 2011 at 12:55 PM, Chad Versace <chad at chad-versace.us> wrote:
> [CC'ing krh because I learned much of this from him, so may have some
> insight to share with us.]
>
> On 08/25/2011 08:14 PM, Chia-I Wu wrote:
>> On Fri, Aug 26, 2011 at 4:09 AM, Chad Versace <chad at chad-versace.us> wrote:
>>> On 08/24/2011 06:20 PM, Chia-I Wu wrote:
>>>> On Thu, Aug 25, 2011 at 8:58 AM, Chad Versace <chad at chad-versace.us> wrote:
>>>> Comments below.
>>>>
>>>> On 08/23/2011 08:10 PM, Chia-I Wu wrote:
>>>>>>> Add platform_android.c that supports _EGL_PLAFORM_ANDROID. It works
>>>>>>> with drm_gralloc, where back buffers of windows are backed by GEM
>>>>>>> objects.
>>>>>>>
>>>>>>> In Android a native window has a queue of back buffers allocated by the
>>>>>>> server, through drm_gralloc. For each frame, EGL needs to
>>>>>>>
>>>>>>> dequeue the next back buffer
>>>>>>> render to the buffer
>>>>>>> enqueue the buffer
>>>>>>>
>>>>>>> After enqueuing, the buffer is no longer valid to EGL. A window has no
>>>>>>> depth buffer or other aux buffers. They need to be allocated locally by
>>>>>>> EGL.
>>>>>>> ---
>>>>>>> src/egl/drivers/dri2/egl_dri2.c | 89 +++++
>>>>>>> src/egl/drivers/dri2/egl_dri2.h | 18 +
>>>>>>> src/egl/drivers/dri2/platform_android.c | 588 +++++++++++++++++++++++++++++++
>>>>>>> 3 files changed, 695 insertions(+), 0 deletions(-)
>>>>>>> create mode 100644 src/egl/drivers/dri2/platform_android.c
>>>>>>>
>>>>>>> diff --git a/src/egl/drivers/dri2/platform_android.c b/src/egl/drivers/dri2/platform_android.c
>>>>>>> new file mode 100644
>>>>>>> index 0000000..d0de94c
>>>>>>> --- /dev/null
>>>>>>> +++ b/src/egl/drivers/dri2/platform_android.c
>>>>
>>>> [snip]
>>>>
>>>>>>> +static _EGLSurface *
>>>>>>> +droid_create_surface(_EGLDriver *drv, _EGLDisplay *disp, EGLint type,
>>>>>>> + _EGLConfig *conf, EGLNativeWindowType window,
>>>>>>> + const EGLint *attrib_list)
>>>>>>> +{
>>>>>>> + struct dri2_egl_display *dri2_dpy = dri2_egl_display(disp);
>>>>>>> + struct dri2_egl_config *dri2_conf = dri2_egl_config(conf);
>>>>>>> + struct dri2_egl_surface *dri2_surf;
>>>>>>> + int format;
>>>>>>> +
>>>>>>> + (void) drv;
>>>>>>> +
>>>>>>> + if (!window || window->common.magic != ANDROID_NATIVE_WINDOW_MAGIC) {
>>>>>>> + _eglError(EGL_BAD_NATIVE_WINDOW, "droid_create_surface");
>>>>>>> + return NULL;
>>>>>>> + }
>>>>>>> + if (window->query(window, NATIVE_WINDOW_FORMAT, &format)) {
>>>>>>> + _eglError(EGL_BAD_NATIVE_WINDOW, "droid_create_surface");
>>>>>>> + return NULL;
>>>>>>> + }
>>>>>>> + if (format != dri2_conf->base.NativeVisualID) {
>>>>>>> + _eglLog(_EGL_WARNING, "Native format mismatch: 0x%x != 0x%x",
>>>>>>> + format, dri2_conf->base.NativeVisualID);
>>>>>>> + }
>>>>>>> +
>>>>>>> + dri2_surf = calloc(1, sizeof *dri2_surf);
>>>>>>> + if (!dri2_surf) {
>>>>>>> + _eglError(EGL_BAD_ALLOC, "droid_create_surface");
>>>>>>> + return NULL;
>>>>>>> + }
>>>>>>> +
>>>>>>> + if (!_eglInitSurface(&dri2_surf->base, disp, type, conf, attrib_list))
>>>>>>> + goto cleanup_surf;
>>>>
>>>> It seems that droid_get_buffers_with_format() only supports single-buffered
>>>> surfaces. So eglCreateWindowSurface should reject requests for which
>>>> EGL_RENDER_BUFFER != EGL_SINGLE_BUFFER.
>>>>
>>>> if (dri2_surf->base.RenderBuffer != EGL_SINGLE_BUFFER)
>>>> goto cleanup_surf;
>>>>> [CC Benjamin]
>>>>> EGL_RENDER_BUFFER is a hint here. It is fine if the native window
>>>>> does not support EGL_SINGLE_BUFFER.
>>>
>>>
>>> You're right, specifying EGL_RENDER_BUFFER in eglCreateWindowSurface is just
>>> a hint. And since the spec says this about eglQuerySurface,
>>> Querying EGL_RENDER_BUFFER returns the buffer which client API rendering
>>> is requested to use. For a window surface, this is the same attribute value specified
>>> when the surface was created.
>>> we shouldn't alter the requested value of dri2_surf->base.RenderBuffer.
>>>
>>>>> On the other hand, ctx->WindowRenderBuffer should be set. It is
>>>>> queried by eglQueryContext. I think it can be set in
>>>>> dri2_create_context: to EGL_BACK_BUFFER when there is
>>>>> dri_double_config and EGL_SINGLE_BUFFER when there is only
>>>>> dri_single_config. Idea?
>>>
>>> I agree that it seems safe to set ctx->WindowRenderBuffer when there is only a
>>> dri_single_config. So, to ensure that the EGLConfig passed to
>>> eglCreateContext does not have a dri_double_config, I think you need
>>> to add this snippet in droid_add_configs_for_visuals:
>>> for (i = 0; visuals[i].format; i++) {
>>> ...
>>> for (j = 0; dri2_dpy->driver_configs[j]; j++) {
>>> ...
>>> /* Maybe this? */
>>> if (dri2_dpy->driver_configs[j]->modes.doubleBufferMode)
>>> continue;
>>> /* end suggestion */
>>>
>>> dri2_conf = dri2_add_config(dpy, dri2_dpy->driver_configs[j],
>>> count + 1, visuals[i].size, EGL_WINDOW_BIT, NULL,
>>> visuals[i].rgba_masks);
>>> Also, the call to dri2_dpy->dri2->createNewDrawable should be passed
>>> dri2_conf->dri_single_config.
>>>
>>> But I am hesitant to set it to EGL_BACK_BUFFER when there is a
>>> dri2_double_config. If the driver supports rendering to a single buffered
>>> surface under a context that supports double-buffering, then, if we had set
>>> ctx->WindowRenderBuffer = EGL_BACK_BUFFER, that would force
>>> eglQueryContext(EGL_RENDER_BUFFER) to always return EGL_BACK_BUFFER, even
>>> when rendering to the single buffered surface.
>> A client can only see the back buffer(s) on Android. There is no
>> single-buffered surface on Android. In that case, reporting
>> EGL_SINGLE_BUFFER means we have to lie about a front buffer and make
>> glFlush/glFinish imply eglSwapBuffers. And out of nowhere, the EGL
>> spec says that OpenGL ES does not support EGL_SINGLE_BUFFER for window
>> surfaces...
>>
>> I think this is one of the gray areas that hasn't been sorted out yet.
>> OpenGL requires a front buffer and GL_DRAW_BUFFER is a GL state that
>> EGL (or GLX) cannot change. It is not clear how
>> eglQueryContext(EGL_RENDER_BUFFER) and glDrawBuffer() interact. On
>> the other hand, OpenGL ES does not require a front buffer and there is
>> no GL_DRAW_BUFFER so EGL has EGL_RENDER_BUFFER to make up for it.
>> Take these into considerations, this issue may be too much for this
>> series to resolve.
>>
>
> Aside from the spec confusion, which is indeed a mess, I'm confused on how
> droid_create_surface and droid_get_buffers_with_format interact. If you could
> clear that up for me, then maybe I would better understand your reply.
>
> Let's walk through the creation of eglCreateWindowSurface with an Intel
> driver on Android, and in the process I will explain why the behavior of
> droid_get_buffers_with_format confuses me.
>
> 1. eglCreateWindowSurface resolves to droid_create_surface
> 2. which calls dri2_dpy->dri2->createDrawable(..., dri2_conf->dri_double_config, ...)
> 3. which resolves to dri2CreateNewDrawable
> 4. which calls driCreateNewDrawable
> 4. which calls psp->DriverAPI.CreateBuffer(..., &config->modes, ...)
> 5. which resolves to intelCreateBuffer(..., mesaVis, ...)
>
> For non-pixamp surfaces, intelCreateBuffer always creates BUFFER_FRONT_LEFT. It
> also creates BUFFER_BACK_LEFT if the mesaVis is double-buffered (which it is in
> this case, because we passed in dri2_conf->dri_double_config).
>
> Sometime before drawing to the surface, the following call sequence occurs on that
> surface (which is here called the drawable).
> 10. intel_update_renderbuffers(..., drawable) is called
> 11. which calls intel_query_dri2_buffers_no_separate_stencil(..., drawable, ...)
> 12. which calls screen->dri2.loader->getBuffersWithFormat(drawable, ...)
> 13. which resolves to droid_get_buffers_with_format(driDrawable, ...)
>
> Before continuing the walkthrough, I'll reproduce droid_get_buffers_with_format for reference.
>
>> +static __DRIbuffer *
>> +droid_get_buffers_with_format(__DRIdrawable * driDrawable,
>> + int *width, int *height,
>> + unsigned int *attachments, int count,
>> + int *out_count, void *loaderPrivate)
>> +{
>> + struct dri2_egl_surface *dri2_surf = loaderPrivate;
>> + struct dri2_egl_display *dri2_dpy =
>> + dri2_egl_display(dri2_surf->base.Resource.Display);
>> + int i;
>> +
>> + if (!dri2_surf->buffer) {
>> + if (!droid_dequeue_buffer(dri2_surf))
>> + return NULL;
>> + }
>> +
>> + /* free outdated buffers and update the surface size */
>> + if (dri2_surf->base.Width != dri2_surf->buffer->width ||
>> + dri2_surf->base.Height != dri2_surf->buffer->height) {
>> + droid_free_local_buffers(dri2_surf);
>> + dri2_surf->base.Width = dri2_surf->buffer->width;
>> + dri2_surf->base.Height = dri2_surf->buffer->height;
>> + }
>> +
>> + dri2_surf->buffer_count = 0;
>> + for (i = 0; i < count * 2; i += 2) {
>> + __DRIbuffer *buf, *local;
>> +
>> + assert(dri2_surf->buffer_count < ARRAY_SIZE(dri2_surf->buffers));
>> + buf = &dri2_surf->buffers[dri2_surf->buffer_count];
>> +
>> + switch (attachments[i]) {
>> + case __DRI_BUFFER_BACK_LEFT:
>> + buf->attachment = attachments[i];
>> + buf->name = get_native_buffer_name(dri2_surf->buffer);
>> + buf->cpp = get_format_bpp(dri2_surf->buffer->format);
>> + buf->pitch = dri2_surf->buffer->stride * buf->cpp;
>> + buf->flags = 0;
>> +
>> + dri2_surf->buffer_count++;
>> + break;
>> + case __DRI_BUFFER_DEPTH:
>> + case __DRI_BUFFER_STENCIL:
>> + case __DRI_BUFFER_ACCUM:
>> + case __DRI_BUFFER_DEPTH_STENCIL:
>> + case __DRI_BUFFER_HIZ:
>> + local = droid_alloc_local_buffer(dri2_surf,
>> + attachments[i], attachments[i + 1]);
>> +
>> + if (local) {
>> + *buf = *local;
>> + dri2_surf->buffer_count++;
>> + }
>> + break;
>> + case __DRI_BUFFER_FRONT_LEFT:
>> + case __DRI_BUFFER_FRONT_RIGHT:
>> + case __DRI_BUFFER_FAKE_FRONT_LEFT:
>> + case __DRI_BUFFER_FAKE_FRONT_RIGHT:
>> + case __DRI_BUFFER_BACK_RIGHT:
>> + default:
>> + /* no front or right buffers */
>> + break;
>> + }
>> + }
>> +
>> + if (width)
>> + *width = dri2_surf->base.Width;
>> + if (height)
>> + *height = dri2_surf->base.Height;
>> +
>> + *out_count = dri2_surf->buffer_count;;
>> +
>> + return dri2_surf->buffers;
>> +}
>
> For a surface created with a single-buffered config, there is a conflict.
> droid_create_surface (via intelCreateBuffer) created a __DRI_BUFFER_FRONT_LEFT,
> but no __DRI_BUFFER_BACK_LEFT, but droid_get_buffers_with_format ignores the
> front-left and handles the back-left.
>
> For a surface created with a double-buffered config, why is the front-left
> ignored, even though dri2_create_surface created a front-left renderbuffer?
>
> Is this due to some quirk of the Android window manager? Did I fail to
> understand something here?
The biggest confusion may come from the fact that on X11, you can
request the front, back, depth, and other aux. buffers. But on
Android, you can only request the back buffer. For each frame, it
works like this
dequeue the next back buffer from the native window
render to the buffer
enqueue the buffer and it will be displayed on screen
There are actually multiple back buffers for a window, but it is
transparent to a client. As for depth or other aux. buffers, they are
supposed to allocated by EGL. As you can see in
droid_get_buffers_with_format, there is no magic at the moment and it
simply returns the buffers it has to offer.
Why this works is because, in the end of dri2_add_config,
EGL_WINDOW_BIT is set only when the EGLConfig has a double buffered
DRI config. That makes sure the contexts that will be created will
have GL_DRAW_BUFFER set to GL_BACK by default. Since there is no
glDrawBuffer(s) in OpenGL ES, it can never be set to GL_FRONT. Though
we have a rb at BUFFER_FRONT_LEFT, its storage is never allocated nor
required. As for EGL_RENDER_BUFFER, IMHO it is best we stay faithful
for now and return EGL_BACK_BUFFER.
There is no pixmap in Android so it can be ignored. As for pbuffers,
which I plan to support as a follow-on commit, it works pretty much
the same as the windows except that the back buffer is also allocated
by EGL.
This works because double-buffered DRI config is used. I considered
fix this, and the fix I had in mind was to remove the idea of single-
or double- buffered contexts[1]. But I haven't had the time to work
on that. Another approach may be to re-route color buffers of a
native window to different __DRI_BUFFER attachments, such as returning
the back buffer as __DRI_BUFFER_FAKE_FRONT_LEFT. But then you need to
make sure a single-buffered DRI config is used, which does not make
the situation better.
[1] http://lists.freedesktop.org/archives/mesa-dev/2011-August/010400.html
>
> --
> Chad Versace
> chad at chad-versace.us
>
>>>>
>>>> I think the DRI2 surface type needs to be set here too.
>>>>
>>>> dri2_surf->type = DRI2_WINDOW_SURFACE;
>>>>> This field seems to be used by wayland only. For the other places,
>>>>> dri2_surf->Base.Type is used.
>>>>>>> +
>>>>>>> + dri2_surf->dri_drawable =
>>>>>>> + (*dri2_dpy->dri2->createNewDrawable)(dri2_dpy->dri_screen,
>>>>>>> + dri2_conf->dri_double_config,
>>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>>
>>> I think dri2_conf->dri_single_config should be passed here.
>>>
>>>>>>> + dri2_surf);
>>>>>>> + if (dri2_surf->dri_drawable == NULL) {
>>>>>>> + _eglError(EGL_BAD_ALLOC, "dri2->createNewDrawable");
>>>>>>> + goto cleanup_surf;
>>>>>>> + }
>>>>>>> +
>>>>>>> + window->common.incRef(&window->common);
>>>>>>> + window->query(window, NATIVE_WINDOW_WIDTH, &dri2_surf->base.Width);
>>>>>>> + window->query(window, NATIVE_WINDOW_HEIGHT, &dri2_surf->base.Height);
>>>>>>> +
>>>>>>> + dri2_surf->window = window;
>>>>>>> +
>>>>>>> + return &dri2_surf->base;
>>>>>>> +
>>>>>>> +cleanup_surf:
>>>>>>> + free(dri2_surf);
>>>>>>> +
>>>>>>> + return NULL;
>>>>>>> +}
>
--
olv at LunarG.com
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