[RFC PATCH 3/3] NOT FOR MERGE: drm/glanda: Add x86 platform test device

[Leander Kieweg <kieweg.leander@gmail.com>]

Register a mock platform device on x86 architectures to allow
testing the GlandaGPU driver inside QEMU without cross-compiling.

Signed-off-by: Leander Kieweg <kieweg.leander@gmail.com>
---
 drivers/gpu/drm/tiny/Kconfig     | 14 ++++++++++++
 drivers/gpu/drm/tiny/glandagpu.c | 39 ++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/drivers/gpu/drm/tiny/Kconfig b/drivers/gpu/drm/tiny/Kconfig
index 7a15bf95a..156713746 100644
--- a/drivers/gpu/drm/tiny/Kconfig
+++ b/drivers/gpu/drm/tiny/Kconfig
@@ -67,6 +67,20 @@ config DRM_GLANDA
 	  basic modesetting, dumb buffers, and simple 2D drawing
 	  acceleration via custom hardware IOCTLs.
 
+config DRM_GLANDA_X86_TEST
+    bool "Register a fixed-address test device on x86 (QEMU only)"
+    depends on DRM_GLANDA && X86
+    default n
+    help
+      Registers a platform device at a hardcoded physical address
+      (0xC0000000) for testing GlandaGPU against a QEMU-based digital
+      twin without needing a devicetree.
+
+      WARNING: this blindly ioremaps a fixed physical address range.
+      Do NOT enable this on real x86 hardware. This exists solely to
+      let reviewers test the driver in QEMU without cross-compiling
+      an ARM kernel/rootfs. Leave disabled otherwise.
+
 config DRM_GM12U320
 	tristate "GM12U320 driver for USB projectors"
 	depends on DRM && USB && MMU
diff --git a/drivers/gpu/drm/tiny/glandagpu.c b/drivers/gpu/drm/tiny/glandagpu.c
index 8f87ae096..c1e9370f2 100644
--- a/drivers/gpu/drm/tiny/glandagpu.c
+++ b/drivers/gpu/drm/tiny/glandagpu.c
@@ -741,6 +741,34 @@ static struct platform_driver glandagpu_driver = {
 	.remove = glandagpu_remove,
 };
 
+#ifdef CONFIG_DRM_GLANDA_X86_TEST
+static struct platform_device *pdev_x86;
+
+static struct resource glandagpu_resources[] = {
+	[0] = {			/* Single resource covering VRAM and MMIO. */
+	       .start = BRIDGE_BASE,
+	       .end = GLANDA_BASE_SIZE,
+	       .flags = IORESOURCE_MEM,},
+	[1] = {			/* IRQ */
+	       .start = 11,
+	       .end = 11,
+	       .flags = IORESOURCE_IRQ,},
+};
+
+static int glandagpu_register_x86_test_device(void)
+{
+	pdev_x86 = platform_device_register_simple("glandagpu", -1,
+						   glandagpu_resources,
+						   ARRAY_SIZE(glandagpu_resources));
+	if (IS_ERR(pdev_x86)) {
+		pr_err("GlandaGPU: Failed to register platform device\n");
+		return PTR_ERR(pdev_x86);
+	}
+
+	return 0;
+}
+#endif
+
 static int __init glandagpu_init(void)
 {
 	int ret;
@@ -750,6 +778,13 @@ static int __init glandagpu_init(void)
 		pr_err("GlandaGPU: Failed to register platform driver\n");
 		return ret;
 	}
+#ifdef CONFIG_DRM_GLANDA_X86_TEST
+	ret = glandagpu_register_x86_test_device();
+	if (ret) {
+		platform_driver_unregister(&glandagpu_driver);
+		return ret;
+	}
+#endif
 
 	pr_info("GlandaGPU: Module loaded successfully\n");
 	return 0;
@@ -757,6 +792,10 @@ static int __init glandagpu_init(void)
 
 static void __exit glandagpu_exit(void)
 {
+#ifdef CONFIG_DRM_GLANDA_X86_TEST
+	if (pdev_x86)
+		platform_device_unregister(pdev_x86);
+#endif
 	platform_driver_unregister(&glandagpu_driver);
 	pr_info("GlandaGPU: Module unloaded\n");
 }
-- 
2.43.0