loader: extend DRI_PRIME to support =N

DRI_PRIME=1 isn't useful on machines with more than 2 GPUs.

This commit adds support to DRI_PRIME=N syntax meaning: select
the Nth GPU (not counting the default GPU).

So on a 3 GPUs system where drmGetDevices2 returns the following:

   /dev/dri/renderD130 [default]
   /dev/dri/renderD129
   /dev/dri/renderD128

DRI_PRIME=1 would select D129 (as is already the case without this
commit), DRI_PRIME=2 would select D128.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24750>

diff --git a/src/loader/loader.c b/src/loader/loader.c
index dce7030..6b4fc9f 100644 (file)
--- a/src/loader/loader.c
+++ b/src/loader/loader.c
@@ -328,11 +328,12 @@ bool loader_get_user_preferred_fd(int *fd_render_gpu, int *original_fd)
    int i, num_devices, fd = -1;
    struct {
       enum {
-         PRIME_IS_ONE,
+         PRIME_IS_INTEGER,
          PRIME_IS_VID_DID,
          PRIME_IS_PCI_TAG
       } semantics;
       union {
+         int as_integer;
          struct {
             uint16_t v, d;
          } as_vendor_device_ids;
@@ -357,10 +358,15 @@ bool loader_get_user_preferred_fd(int *fd_render_gpu, int *original_fd)
          prime.v.as_vendor_device_ids.v = vendor_id;
          prime.v.as_vendor_device_ids.d = device_id;
       } else {
-         if (strcmp(prime.str, "1") == 0) {
-            prime.semantics = PRIME_IS_ONE;
-         } else {
+         int i = atoi(prime.str);
+         if (i < 0 || strcmp(prime.str, "0") == 0) {
+            printf("Invalid value (%d) for DRI_PRIME. Should be > 0\n", i);
+            goto err;
+         } else if (i == 0) {
             prime.semantics = PRIME_IS_PCI_TAG;
+         } else {
+            prime.semantics = PRIME_IS_INTEGER;
+            prime.v.as_integer = i;
          }
       }
    }
@@ -373,6 +379,14 @@ bool loader_get_user_preferred_fd(int *fd_render_gpu, int *original_fd)
    if (num_devices <= 0)
       goto err;
 
+   if (prime.semantics == PRIME_IS_INTEGER &&
+       prime.v.as_integer >= num_devices) {
+      printf("Inconsistent value (%d) for DRI_PRIME. Should be < %d "
+             "(GPU devices count). Using: %d\n",
+             prime.v.as_integer, num_devices, num_devices - 1);
+      prime.v.as_integer = num_devices - 1;
+   }
+
    for (i = 0; i < num_devices; i++) {
       if (!(devices[i]->available_nodes & 1 << DRM_NODE_RENDER))
          continue;
@@ -385,10 +399,15 @@ bool loader_get_user_preferred_fd(int *fd_render_gpu, int *original_fd)
        * vendor_id:device_id
        */
       switch (prime.semantics) {
-         case PRIME_IS_ONE: {
+         case PRIME_IS_INTEGER: {
             /* Skip the default device */
             if (drm_device_matches_tag(devices[i], default_tag))
                continue;
+            prime.v.as_integer--;
+
+            /* Skip more GPUs? */
+            if (prime.v.as_integer)
+               continue;
 
             break;
          }
@@ -405,9 +424,9 @@ bool loader_get_user_preferred_fd(int *fd_render_gpu, int *original_fd)
             continue;
          }
          case PRIME_IS_PCI_TAG: {
-            if (!drm_device_matches_tag(devices[i], prime.str)) {
+            if (!drm_device_matches_tag(devices[i], prime.str))
                continue;
-            }
+
             break;
          }
       }