[waffle] [PATCH 5/7] surfaceless_egl: Implement new platform

[Emil Velikov]

On 29 October 2016 at 18:59, Chad Versace <chadversary at chromium.org> wrote:
> On Wed 19 Oct 2016, Emil Velikov wrote:
>> On 18 October 2016 at 18:33, Chad Versace <chadversary at chromium.org> wrote:
>> > Now waffle_init() supports WAFFLE_PLATFORM_SURFACELESS_EGL.
>> >
>> > Cc: Gurchetan Singh <gurchetansingh at chromium.org>
>> > Cc: Haixia Shi <hshi at chromium.org>
>> > ---
>> >  include/waffle/waffle.h                  |   1 +
>> >  man/waffle_init.3.xml                    |   9 ++
>> >  src/waffle/CMakeLists.txt                |   9 ++
>> >  src/waffle/api/waffle_init.c             |  12 +++
>> >  src/waffle/egl/wegl_platform.c           |   6 ++
>> >  src/waffle/surfaceless_egl/sl_display.c  |  70 +++++++++++++++
>> >  src/waffle/surfaceless_egl/sl_display.h  |  45 ++++++++++
>> >  src/waffle/surfaceless_egl/sl_platform.c | 144 +++++++++++++++++++++++++++++++
>> >  src/waffle/surfaceless_egl/sl_platform.h |  49 +++++++++++
>> >  src/waffle/surfaceless_egl/sl_window.c   |  92 ++++++++++++++++++++
>> >  src/waffle/surfaceless_egl/sl_window.h   |  53 ++++++++++++
>> >  11 files changed, 490 insertions(+)
>> >  create mode 100644 src/waffle/surfaceless_egl/sl_display.c
>> >  create mode 100644 src/waffle/surfaceless_egl/sl_display.h
>> >  create mode 100644 src/waffle/surfaceless_egl/sl_platform.c
>> >  create mode 100644 src/waffle/surfaceless_egl/sl_platform.h
>> >  create mode 100644 src/waffle/surfaceless_egl/sl_window.c
>> >  create mode 100644 src/waffle/surfaceless_egl/sl_window.h
>> >
>
>> Should there be an extra case in src/waffle/core/wcore_util.c's
>> wcore_enum_to_string() ?
>
> Oops. I squashed the fix into this patch.
>
>> > +// [chadv] I regret the design of the get_native interface, and wish to
>> > +// deprecate and replace it with the interface that Ian Romanick orignally
>> > +// recommended: waffle_display_get_egl_display(),
>> > +// waffle_display_get_gbm_device(), waffle_display_get_xlib_display(), etc.  As
>> > +// a first step towards that goal, I choose to not support the interface on new
>> > +// platforms.
>
>> Silly question: what's wrong with the current [generic] get_native_{foo,bar} ?
>
> Each get_native function returns a non-extensible struct. The problem is
> the non-extensibility.
>
>     Example 1:
>
>         On Wayland, waffle_window_get_window() returns
>
>             struct waffle_wayland_window {
>                 struct waffle_wayland_display display; // Definition below
>                 struct wl_surface *wl_surface;
>                 struct wl_shell_surface *wl_shell_surface;
>                 struct wl_egl_window *wl_window;
>                 EGLSurface egl_surface;
>             };
>
>             struct waffle_wayland_display {
>                 struct wl_display *wl_display;
>                 struct wl_compositor *wl_compositor;
>                 struct wl_shell *wl_shell;
>                 EGLDisplay egl_display;
>             };
>
>         If in the future we need to add more members to that struct, or even remove
>         members, due to changes in Wayland, then there is no good way to do that.
>
>     Example 2:
>
>         I want to add the ability to do KMS with waffle_window/waffle_display on
>         the gbm and surfaceless platforms. Again, because the get_native structs
>         are non-extensible, there is no good way for
>         waffle_window_get_native()/waffle_display_get_native() to return things
>         such as the CRTC.
>
> So I see two solutions:
>
>     Solution 1: Change the get_native APIs to return "extensible" structs. If
>         someone is going to go through all that trouble, though, they might as
>         well go with solution 2, which is cleaner and less work.
>
>     Solution 2: For each possible native resourse of each Waffle resource, add
>     a specific getter that returns null-or-whatever if it doesn't exist.  For example,
>
>         EGLSurface waffle_window_get_egl_surface(...);
>         struct gbm_surface *waffle_window_get_gbm_surface(...);

IMHO the only part that prevents one to extend the structs is the
embedded waffle_$platform_display into the confirg/context/window
structs. With those converted to struct * things should be just fine.
On the removal side - I cannot think of any way to make that happen
w/o breaking the API/ABI. Be that with the current or proposed
solution.

If anything I'd opt/suggest the struct * route since it will results
in less code - within waffle, its API and the users.
The work for ^^ will be mostly copy/paste afaics.

Emil