gallium: Add a dumb drm/kms winsys backed swrast provider

Add a new winsys and target that can be used with a dri2 state tracker
and loader instead of drisw. This allows to use gbm as a dri2/image
loader and avoid the extra copy from the backbuffer to the shadow
frontbuffer.

The new driver is called "kms_swrast", and is loaded by gbm as a
fallback, because it is only useful with the gbm platform (as no buffer
sharing is possible)

To force select the driver set the environment variable
GBM_ALWAYS_SOFTWARE

[Emil Velikov]
 - Rebase on top of gallium megadriver.
 - s/text/test/ in configure.ac (Spotted by Andreas Pokorny).
 - Add scons support for winsys/sw/kms-dri and fix the build.
 - Provide separate DriverAPI, due to different InitScreen hook.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

1 files changed, 34 insertions, 4 deletions

diff --git a/src/gbm/backends/dri/gbm_dri.c b/src/gbm/backends/dri/gbm_dri.c
index 7b28be1ba0..258e8a84a6 100644
--- a/src/gbm/backends/dri/gbm_dri.c
+++ b/src/gbm/backends/dri/gbm_dri.c
@@ -403,12 +403,13 @@ dri_load_driver_swrast(struct gbm_dri_device *dri)
 }
 
 static int
-dri_screen_create(struct gbm_dri_device *dri)
+dri_screen_create_dri2(struct gbm_dri_device *dri,
+                       const char *driver_name)
 {
    const __DRIextension **extensions;
    int ret = 0;
 
-   dri->base.driver_name = loader_get_driver_for_fd(dri->base.base.fd, 0);
+   dri->base.driver_name = driver_name;
    if (dri->base.driver_name == NULL)
       return -1;
 
@@ -491,6 +492,35 @@ dri_screen_create_swrast(struct gbm_dri_device *dri)
 }
 
 static int
+dri_screen_create(struct gbm_dri_device *dri)
+{
+   const char *driver_name;
+
+   driver_name = loader_get_driver_for_fd(dri->base.base.fd, 0);
+   if (!driver_name)
+      return -1;
+
+   return dri_screen_create_dri2(dri, driver_name);
+}
+
+static int
+dri_screen_create_sw(struct gbm_dri_device *dri)
+{
+   const char *driver_name;
+   int ret;
+
+   driver_name = strdup("kms_swrast");
+   if (!driver_name)
+      return -errno;
+
+   ret = dri_screen_create_dri2(dri, driver_name);
+   if (ret == 0)
+      return ret;
+
+   return dri_screen_create_swrast(dri);
+}
+
+static int
 gbm_dri_is_format_supported(struct gbm_device *gbm,
                             uint32_t format,
                             uint32_t usage)
@@ -920,9 +950,9 @@ dri_device_create(int fd)
    if (!force_sw) {
       ret = dri_screen_create(dri);
       if (ret)
-         ret = dri_screen_create_swrast(dri);
+         ret = dri_screen_create_sw(dri);
    } else {
-      ret = dri_screen_create_swrast(dri);
+      ret = dri_screen_create_sw(dri);
    }
 
    if (ret)