drm/vkms: Introduce basic VKMS driver

This patch introduces Virtual Kernel Mode-Setting (VKMS) driver. It
creates a very basic kms driver with 1 crtc/encoder/connector/plane.

VKMS driver would be useful for testing, or for running X (or similar)
on headless machines and be able to still use the GPU. Thus it enables
a virtual display without the need for hardware display capability.

Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180514143346.GA21695@haneen-vb

5 files changed, 169 insertions, 0 deletions

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 2a72d2feb76d..7db3d82cbb27 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -213,6 +213,12 @@ config DRM_VGEM
           as used by Mesa's software renderer for enhanced performance.
           If M is selected the module will be called vgem.
 
+config DRM_VKMS
+        tristate "Virtual KMS"
+        depends on DRM
+        help
+          Choose this option to get a virtual kernal mode-setting driver.
+          If M is selected the module will be called vkms.
 
 source "drivers/gpu/drm/exynos/Kconfig"
 
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 69c13517ea3a..6ae535ca0914 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -69,6 +69,7 @@ obj-$(CONFIG_DRM_SAVAGE)+= savage/
 obj-$(CONFIG_DRM_VMWGFX)+= vmwgfx/
 obj-$(CONFIG_DRM_VIA)   +=via/
 obj-$(CONFIG_DRM_VGEM)  += vgem/
+obj-$(CONFIG_DRM_VKMS)  += vkms/
 obj-$(CONFIG_DRM_NOUVEAU) +=nouveau/
 obj-$(CONFIG_DRM_EXYNOS) +=exynos/
 obj-$(CONFIG_DRM_ROCKCHIP) +=rockchip/
diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
new file mode 100644
index 000000000000..2aef948d3a34
--- /dev/null
+++ b/drivers/gpu/drm/vkms/Makefile
@@ -0,0 +1,3 @@
+vkms-y := vkms_drv.o
+
+obj-$(CONFIG_DRM_VKMS) += vkms.o
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
new file mode 100644
index 000000000000..b1df08ed23a0
--- /dev/null
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -0,0 +1,146 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <drm/drmP.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_crtc_helper.h>
+#include "vkms_drv.h"
+
+#define DRIVER_NAME     "vkms"
+#define DRIVER_DESC     "Virtual Kernel Mode Setting"
+#define DRIVER_DATE     "20180514"
+#define DRIVER_MAJOR    1
+#define DRIVER_MINOR    0
+
+static struct vkms_device *vkms_device;
+
+static const struct file_operations vkms_driver_fops = {
+        .owner          = THIS_MODULE,
+        .open           = drm_open,
+        .mmap           = drm_gem_mmap,
+        .unlocked_ioctl = drm_ioctl,
+        .compat_ioctl   = drm_compat_ioctl,
+        .poll           = drm_poll,
+        .read           = drm_read,
+        .llseek         = no_llseek,
+        .release        = drm_release,
+};
+
+static void vkms_release(struct drm_device *dev)
+{
+        struct vkms_device *vkms = container_of(dev, struct vkms_device, drm);
+
+        platform_device_unregister(vkms->platform);
+        drm_mode_config_cleanup(&vkms->drm);
+        drm_dev_fini(&vkms->drm);
+}
+
+struct drm_driver vkms_driver = {
+        .driver_features        = DRIVER_MODESET | DRIVER_ATOMIC | DRIVER_GEM,
+        .release                = vkms_release,
+        .fops                   = &vkms_driver_fops,
+
+        .name                   = DRIVER_NAME,
+        .desc                   = DRIVER_DESC,
+        .date                   = DRIVER_DATE,
+        .major                  = DRIVER_MAJOR,
+        .minor                  = DRIVER_MINOR,
+};
+
+static const u32 vkms_formats[] = {
+        DRM_FORMAT_XRGB8888,
+};
+
+static void vkms_connector_destroy(struct drm_connector *connector)
+{
+        drm_connector_unregister(connector);
+        drm_connector_cleanup(connector);
+}
+
+static const struct drm_connector_funcs vkms_connector_funcs = {
+        .fill_modes = drm_helper_probe_single_connector_modes,
+        .destroy = vkms_connector_destroy,
+};
+
+static int __init vkms_init(void)
+{
+        int ret;
+
+        vkms_device = kzalloc(sizeof(*vkms_device), GFP_KERNEL);
+        if (!vkms_device)
+                return -ENOMEM;
+
+        ret = drm_dev_init(&vkms_device->drm, &vkms_driver, NULL);
+        if (ret)
+                goto out_free;
+
+        vkms_device->platform =
+                platform_device_register_simple(DRIVER_NAME, -1, NULL, 0);
+        if (IS_ERR(vkms_device->platform)) {
+                ret = PTR_ERR(vkms_device->platform);
+                goto out_fini;
+        }
+
+        drm_mode_config_init(&vkms_device->drm);
+
+        ret = drm_connector_init(&vkms_device->drm, &vkms_device->connector,
+                                 &vkms_connector_funcs,
+                                 DRM_MODE_CONNECTOR_VIRTUAL);
+        if (ret < 0) {
+                DRM_ERROR("Failed to init connector\n");
+                goto out_unregister;
+        }
+
+        ret = drm_simple_display_pipe_init(&vkms_device->drm,
+                                           &vkms_device->pipe,
+                                           NULL,
+                                           vkms_formats,
+                                           ARRAY_SIZE(vkms_formats),
+                                           NULL,
+                                           &vkms_device->connector);
+        if (ret < 0) {
+                DRM_ERROR("Cannot setup simple display pipe\n");
+                goto out_unregister;
+        }
+
+        ret = drm_dev_register(&vkms_device->drm, 0);
+        if (ret)
+                goto out_unregister;
+
+        drm_connector_register(&vkms_device->connector);
+
+        return 0;
+
+out_unregister:
+        platform_device_unregister(vkms_device->platform);
+out_fini:
+        drm_dev_fini(&vkms_device->drm);
+out_free:
+        kfree(vkms_device);
+
+        return ret;
+}
+
+static void __exit vkms_exit(void)
+{
+        if (!vkms_device) {
+                DRM_INFO("vkms_device is NULL.\n");
+                return;
+        }
+
+        drm_dev_unregister(&vkms_device->drm);
+        drm_dev_put(&vkms_device->drm);
+
+        kfree(vkms_device);
+}
+
+module_init(vkms_init);
+module_exit(vkms_exit);
+
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
new file mode 100644
index 000000000000..c77c5bf5032a
--- /dev/null
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -0,0 +1,13 @@
+#ifndef _VKMS_DRV_H_
+#define _VKMS_DRV_H_
+
+#include <drm/drm_simple_kms_helper.h>
+
+struct vkms_device {
+        struct drm_device drm;
+        struct platform_device *platform;
+        struct drm_simple_display_pipe pipe;
+        struct drm_connector connector;
+};
+
+#endif /* _VKMS_DRV_H_ */