From a3e0637aa224b31438a8ae550344362ee02a327b Mon Sep 17 00:00:00 2001
Message-Id: <a3e0637aa224b31438a8ae550344362ee02a327b@dist-git>
From: Erik Skultety <eskultet@redhat.com>
Date: Tue, 9 Apr 2019 08:34:25 +0200
Subject: [PATCH] util: Introduce virHostGetDRMRenderNode helper
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This is the first step towards libvirt picking the first available
render node instead of QEMU. It also makes sense for us to be able to do
that, since we allow specifying the node directly for SPICE, so if
there's no render node specified by the user, we should pick the first
available one. The algorithm used for that is essentially the same as
the one QEMU uses.

Signed-off-by: Erik Skultety <eskultet@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
(cherry picked from commit 394809694a5bcb6e1e6890f360c60993c0b63a74)

https: //bugzilla.redhat.com/show_bug.cgi?id=1628892
Signed-off-by: Erik Skultety <eskultet@redhat.com>
Message-Id: <48159f44f12685eb8c52061e09c27e37a5a157ea.1554791287.git.eskultet@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
---
 src/libvirt_private.syms |  1 +
 src/util/virutil.c       | 53 ++++++++++++++++++++++++++++++++++++++++
 src/util/virutil.h       |  2 ++
 3 files changed, 56 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index af9b61fbdc..6655dfdecc 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3116,6 +3116,7 @@ virGetUserName;
 virGetUserRuntimeDirectory;
 virGetUserShell;
 virHexToBin;
+virHostGetDRMRenderNode;
 virHostHasIOMMU;
 virIndexToDiskName;
 virIsDevMapperDevice;
diff --git a/src/util/virutil.c b/src/util/virutil.c
index a908422feb..b25d2a5ca4 100644
--- a/src/util/virutil.c
+++ b/src/util/virutil.c
@@ -2115,3 +2115,56 @@ virHostHasIOMMU(void)
     VIR_DIR_CLOSE(iommuDir);
     return ret;
 }
+
+
+/**
+ * virHostGetDRMRenderNode:
+ *
+ * Picks the first DRM render node available. Missing DRI or missing DRM render
+ * nodes in the system results in an error.
+ *
+ * Returns an absolute path to the first render node available or NULL in case
+ * of an error with the error being reported.
+ * Caller is responsible for freeing the result string.
+ *
+ */
+char *
+virHostGetDRMRenderNode(void)
+{
+    char *ret = NULL;
+    DIR *driDir = NULL;
+    const char *driPath = "/dev/dri";
+    struct dirent *ent = NULL;
+    int dirErr = 0;
+    bool have_rendernode = false;
+
+    if (virDirOpen(&driDir, driPath) < 0)
+        return NULL;
+
+    while ((dirErr = virDirRead(driDir, &ent, driPath)) > 0) {
+        if (ent->d_type != DT_CHR)
+            continue;
+
+        if (STRPREFIX(ent->d_name, "renderD")) {
+            have_rendernode = true;
+            break;
+        }
+    }
+
+    if (dirErr < 0)
+        goto cleanup;
+
+    /* even if /dev/dri exists, there might be no renderDX nodes available */
+    if (!have_rendernode) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("No DRM render nodes available"));
+        goto cleanup;
+    }
+
+    if (virAsprintf(&ret, "%s/%s", driPath, ent->d_name) < 0)
+        goto cleanup;
+
+ cleanup:
+    VIR_DIR_CLOSE(driDir);
+    return ret;
+}
diff --git a/src/util/virutil.h b/src/util/virutil.h
index 1ba9635bd9..284c713be4 100644
--- a/src/util/virutil.h
+++ b/src/util/virutil.h
@@ -218,6 +218,8 @@ unsigned long long virMemoryMaxValue(bool ulong) ATTRIBUTE_NOINLINE;
 
 bool virHostHasIOMMU(void);
 
+char *virHostGetDRMRenderNode(void);
+
 /**
  * VIR_ASSIGN_IS_OVERFLOW:
  * @rvalue: value that is checked (evaluated twice)
-- 
2.21.0