loader: handle picking zink for nouveau for certain GPUs.

This adds NOUVEAU_USE_ZINK env var, but also has commented out
code to pick it for turing+ if mesa is built with nvk and zink.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27628>

meson.build

@@ -319,6 +319,11 @@ with_any_intel = [
 ].contains(true)
 with_any_nouveau = with_gallium_nouveau or with_nouveau_vk
 
+# needed in the loader
+if with_nouveau_vk
+  pre_args += '-DHAVE_NVK'
+endif
+
 if with_swrast_vk and not with_gallium_softpipe
   error('swrast vulkan requires gallium swrast')
 endif

src/loader/loader.c

@@ -54,6 +54,8 @@
 #include "util/u_debug.h"
 #include "git_sha1.h"
 
+#include "drm-uapi/nouveau_drm.h"
+
 #define MAX_DRM_DEVICES 64
 
 #ifdef USE_DRICONF
@@ -123,7 +125,7 @@ loader_get_kernel_driver_name(int fd)
 }
 
 bool
-iris_predicate(int fd)
+iris_predicate(int fd, const char *driver)
 {
    char *kernel_driver = loader_get_kernel_driver_name(fd);
    bool ret = kernel_driver && (strcmp(kernel_driver, "i915") == 0 ||
@@ -133,6 +135,37 @@ iris_predicate(int fd)
    return ret;
 }
 
+/* choose zink or nouveau GL */
+bool
+nouveau_zink_predicate(int fd, const char *driver)
+{
+#if !defined(HAVE_NVK) || !defined(HAVE_ZINK)
+   if (!strcmp(driver, "zink"))
+      return false;
+   return true;
+#else
+
+   bool prefer_zink = false;
+
+   /* enable this once zink is up to speed.
+    * struct drm_nouveau_getparam r = { .param = NOUVEAU_GETPARAM_CHIPSET_ID };
+    * int ret = drmCommandWriteRead(fd, DRM_NOUVEAU_GETPARAM, &r, sizeof(r));
+    * if (ret == 0 && (r.value & ~0xf) >= 0x160)
+    *    prefer_zink = true;
+    */
+
+   prefer_zink = debug_get_bool_option("NOUVEAU_USE_ZINK", prefer_zink);
+
+   if (prefer_zink && !strcmp(driver, "zink"))
+      return true;
+
+   if (!prefer_zink && !strcmp(driver, "nouveau"))
+      return true;
+   return false;
+#endif
+}
+
+
 /**
  * Goes through all the platform devices whose driver is on the given list and
  * try to open their render node. It returns the fd of the first device that
@@ -643,7 +676,7 @@ loader_get_pci_driver(int fd)
       if (vendor_id != driver_map[i].vendor_id)
          continue;
 
-      if (driver_map[i].predicate && !driver_map[i].predicate(fd))
+      if (driver_map[i].predicate && !driver_map[i].predicate(fd, driver_map[i].driver))
          continue;
 
       if (driver_map[i].num_chips_ids == -1) {

src/loader/pci_id_driver_map.h

@@ -44,14 +44,15 @@ static const int vmwgfx_chip_ids[] = {
 #undef CHIPSET
 };
 
-bool iris_predicate(int fd);
+bool iris_predicate(int fd, const char *driver);
+bool nouveau_zink_predicate(int fd, const char *driver);
 
 static const struct {
    int vendor_id;
    const char *driver;
    const int *chip_ids;
    int num_chips_ids;
-   bool (*predicate)(int fd);
+   bool (*predicate)(int fd, const char *driver);
 } driver_map[] = {
    { 0x8086, "i915", i915_chip_ids, ARRAY_SIZE(i915_chip_ids) },
    { 0x8086, "crocus", crocus_chip_ids, ARRAY_SIZE(crocus_chip_ids) },
@@ -59,7 +60,8 @@ static const struct {
    { 0x1002, "r300", r300_chip_ids, ARRAY_SIZE(r300_chip_ids) },
    { 0x1002, "r600", r600_chip_ids, ARRAY_SIZE(r600_chip_ids) },
    { 0x1002, "radeonsi", NULL, -1 },
-   { 0x10de, "nouveau", NULL, -1, },
+   { 0x10de, "nouveau", NULL, -1, nouveau_zink_predicate },
+   { 0x10de, "zink", NULL, -1, nouveau_zink_predicate },
    { 0x1af4, "virtio_gpu", virtio_gpu_chip_ids, ARRAY_SIZE(virtio_gpu_chip_ids) },
    { 0x15ad, "vmwgfx", vmwgfx_chip_ids, ARRAY_SIZE(vmwgfx_chip_ids) },
 };