From: jsg <jsg@openbsd.org>
Date: Tue, 1 Oct 2024 06:41:22 +0000 (+0000)
Subject: drm: Expand max DRM device number to full MINORBITS
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=a163f57acf813fb4f0cc1b7d0b3ffd9392710920;p=openbsd

drm: Expand max DRM device number to full MINORBITS

From Michal Winiarski
e615cd84dcf834e83b333bfb690fc2032b3fdb85 in linux-6.6.y/6.6.53
071d583e01c88272f6ff216d4f867f8f35e94d7d in mainline linux
---

diff --git a/sys/dev/pci/drm/drm_drv.c b/sys/dev/pci/drm/drm_drv.c
index 06f6e78514a..53352d635a9 100644
--- a/sys/dev/pci/drm/drm_drv.c
+++ b/sys/dev/pci/drm/drm_drv.c
@@ -184,10 +184,19 @@ static void drm_minor_alloc_release(struct drm_device *dev, void *data)
 	xa_erase(drm_minor_get_xa(minor->type), minor->index);
 }
 
+/*
+ * DRM used to support 64 devices, for backwards compatibility we need to maintain the
+ * minor allocation scheme where minors 0-63 are primary nodes, 64-127 are control nodes,
+ * and 128-191 are render nodes.
+ * After reaching the limit, we're allocating minors dynamically - first-come, first-serve.
+ * Accel nodes are using a distinct major, so the minors are allocated in continuous 0-MAX
+ * range.
+ */
 #define DRM_MINOR_LIMIT(t) ({ \
 	typeof(t) _t = (t); \
 	_t == DRM_MINOR_ACCEL ? XA_LIMIT(0, ACCEL_MAX_MINORS) : XA_LIMIT(64 * _t, 64 * _t + 63); \
 })
+#define DRM_EXTENDED_MINOR_LIMIT XA_LIMIT(192, (1 << MINORBITS) - 1)
 
 static int drm_minor_alloc(struct drm_device *dev, enum drm_minor_type type)
 {
@@ -203,6 +212,9 @@ static int drm_minor_alloc(struct drm_device *dev, enum drm_minor_type type)
 
 	r = xa_alloc(drm_minor_get_xa(type), &minor->index,
 		     NULL, DRM_MINOR_LIMIT(type), GFP_KERNEL);
+	if (r == -EBUSY && (type == DRM_MINOR_PRIMARY || type == DRM_MINOR_RENDER))
+		r = xa_alloc(&drm_minors_xa, &minor->index,
+			     NULL, DRM_EXTENDED_MINOR_LIMIT, GFP_KERNEL);
 	if (r < 0)
 		return r;