[RFC v4 22/25] drm/fb-helper: Add generic fbdev emulation

["Noralf Trønnes" <noralf@tronnes.org>]

This adds generic fbdev emulation for drivers that supports
dumb buffers which they can export.

All the driver has to do is call drm_fbdev_generic_setup().

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
 drivers/gpu/drm/drm_fb_helper.c | 255 ++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_fb_helper.h     |  20 ++++
 2 files changed, 275 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index b1124c08b1ed..1954de5b13e0 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -30,6 +30,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/console.h>
+#include <linux/dma-buf.h>
 #include <linux/kernel.h>
 #include <linux/sysrq.h>
 #include <linux/slab.h>
@@ -1995,6 +1996,260 @@ void drm_fb_helper_output_poll_changed(struct drm_device *dev)
 }
 EXPORT_SYMBOL(drm_fb_helper_output_poll_changed);
 
+static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+
+	return dma_buf_mmap(fb_helper->buffer->dma_buf, vma, 0);
+}
+
+/*
+ * fb_ops.fb_destroy is called by the last put_fb_info() call at the end of
+ * unregister_framebuffer() or fb_release().
+ */
+static void drm_fbdev_fb_destroy(struct fb_info *info)
+{
+	struct drm_fb_helper *fb_helper = info->par;
+	struct fb_ops *fbops = NULL;
+
+	DRM_DEBUG("\n");
+
+	if (fb_helper->fbdev->fbdefio)
+		fbops = fb_helper->fbdev->fbops;
+
+	drm_fb_helper_fini(fb_helper);
+	drm_client_framebuffer_delete(fb_helper->buffer);
+	drm_client_free(fb_helper->client);
+	kfree(fb_helper);
+	kfree(fbops);
+}
+
+static struct fb_ops drm_fbdev_fb_ops = {
+	/*
+	 * No need to set owner, this module is already pinned by the driver.
+	 * A reference is taken on the driver module in drm_fb_helper_fb_open()
+	 * to prevent the driver going away with open fd's.
+	 */
+	DRM_FB_HELPER_DEFAULT_OPS,
+	.fb_open	= drm_fb_helper_fb_open,
+	.fb_release	= drm_fb_helper_fb_release,
+	.fb_destroy	= drm_fbdev_fb_destroy,
+	.fb_mmap	= drm_fbdev_fb_mmap,
+	.fb_read	= drm_fb_helper_sys_read,
+	.fb_write	= drm_fb_helper_sys_write,
+	.fb_fillrect	= drm_fb_helper_sys_fillrect,
+	.fb_copyarea	= drm_fb_helper_sys_copyarea,
+	.fb_imageblit	= drm_fb_helper_sys_imageblit,
+};
+
+static struct fb_deferred_io drm_fbdev_defio = {
+	.delay		= HZ / 20,
+	.deferred_io	= drm_fb_helper_deferred_io,
+};
+
+/* Hack to test tinydrm before converting to vmalloc buffers */
+static int drm_fbdev_cma_deferred_io_mmap(struct fb_info *info,
+					  struct vm_area_struct *vma)
+{
+	fb_deferred_io_mmap(info, vma);
+	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+
+	return 0;
+}
+
+static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
+				       struct drm_fb_helper_surface_size *sizes)
+{
+	struct drm_client_dev *client = fb_helper->client;
+	struct drm_display_mode sizes_mode = {
+		.hdisplay = sizes->surface_width,
+		.vdisplay = sizes->surface_height,
+	};
+	struct drm_client_buffer *buffer;
+	struct drm_framebuffer *fb;
+	struct fb_info *fbi;
+	u32 format;
+	int ret;
+
+	DRM_DEBUG_KMS("surface width(%d), height(%d) and bpp(%d)\n",
+		      sizes->surface_width, sizes->surface_height,
+		      sizes->surface_bpp);
+
+	format = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth);
+	buffer = drm_client_framebuffer_create(client, &sizes_mode, format);
+	if (IS_ERR(buffer))
+		return PTR_ERR(buffer);
+
+	fb_helper->buffer = buffer;
+	fb_helper->fb = buffer->fb;
+	fb = buffer->fb;
+
+	fbi = drm_fb_helper_alloc_fbi(fb_helper);
+	if (IS_ERR(fbi)) {
+		ret = PTR_ERR(fbi);
+		goto err_free_buffer;
+	}
+
+	fbi->par = fb_helper;
+	fbi->fbops = &drm_fbdev_fb_ops;
+	fbi->screen_size = fb->height * fb->pitches[0];
+	fbi->fix.smem_len = fbi->screen_size;
+	fbi->screen_buffer = buffer->vaddr;
+	strcpy(fbi->fix.id, "DRM emulated");
+
+	drm_fb_helper_fill_fix(fbi, fb->pitches[0], fb->format->depth);
+	drm_fb_helper_fill_var(fbi, fb_helper, sizes->fb_width, sizes->fb_height);
+
+	/*
+	 * Drivers that set the dirty callback:
+	 * - Doesn't use defio:
+	 *   i915, virtio, rockchip
+	 * - defio with vmalloc buffer blitted on the real one:
+	 *   vmwgfx
+	 * - defio is disabled because it doesn't work with shmem:
+	 *   udl
+	 * - defio with special dirty callback for fbdev, uses vmalloc for fbdev:
+	 *   qxl
+	 * - defio with cma buffer, will move to vmalloc buffers:
+	 *   tinydrm
+	 *
+	 * TODO:
+	 * Maybe add vmalloc shadow buffer support.
+	 */
+
+	if (fb->funcs->dirty) {
+		struct fb_ops *fbops;
+
+		/*
+		 * fb_deferred_io_cleanup() clears &fbops->fb_mmap so a per
+		 * instance version is necessary.
+		 */
+		fbops = kzalloc(sizeof(*fbops), GFP_KERNEL);
+		if (!fbops) {
+			ret = -ENOMEM;
+			goto err_fb_info_destroy;
+		}
+
+		*fbops = *fbi->fbops;
+		fbi->fbops = fbops;
+
+		fbi->fbdefio = &drm_fbdev_defio;
+
+		/* Hack so I can test with tinydrm */
+		fbi->fix.smem_start = page_to_phys(virt_to_page(buffer->vaddr));
+
+		fb_deferred_io_init(fbi);
+
+		/* Hack so I can test with tinydrm */
+		fbi->fbops->fb_mmap = drm_fbdev_cma_deferred_io_mmap;
+	}
+
+	return 0;
+
+err_fb_info_destroy:
+	drm_fb_helper_fini(fb_helper);
+err_free_buffer:
+	drm_client_framebuffer_delete(buffer);
+
+	return ret;
+}
+
+static const struct drm_fb_helper_funcs drm_fb_helper_generic_funcs = {
+	.fb_probe = drm_fb_helper_generic_probe,
+};
+
+static int drm_fbdev_client_remove(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = client->private;
+
+	if (!fb_helper->fbdev) {
+		kfree(fb_helper);
+		return 0;
+	}
+
+	unregister_framebuffer(fb_helper->fbdev);
+
+	/*
+	 * If userspace is closed the client is now freed by
+	 * drm_fbdev_fb_destroy(), otherwise it will be freed on the last close.
+	 * Return 1 to tell that freeing is taken care of.
+	 */
+
+	return 1;
+}
+
+static int drm_fbdev_client_lastclose(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = client->private;
+
+	drm_fb_helper_restore_fbdev_mode_unlocked(fb_helper);
+
+	return 0;
+}
+
+static int drm_fbdev_client_hotplug(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = client->private;
+
+	if (fb_helper->fbdev)
+		return 0;
+
+	return drm_fb_helper_fbdev_setup(client->dev, fb_helper,
+					 &drm_fb_helper_generic_funcs,
+					 fb_helper->preferred_bpp, 0);
+}
+
+static const struct drm_client_funcs drm_fbdev_client_funcs = {
+	.name		= "fbdev",
+	.remove		= drm_fbdev_client_remove,
+	.lastclose	= drm_fbdev_client_lastclose,
+	.hotplug	= drm_fbdev_client_hotplug,
+};
+
+/**
+ * drm_fb_helper_generic_fbdev_setup() - Setup generic fbdev emulation
+ * @dev: DRM device
+ * @preferred_bpp: Preferred bits per pixel for the device.
+ *                 @dev->mode_config.preferred_depth is used if this is zero.
+ *
+ * This function sets up generic fbdev emulation for drivers that supports
+ * dumb buffers which can be exported.
+ *
+ * Restore, hotplug events and teardown are all taken care of. Drivers that does
+ * suspend/resume need to call drm_fb_helper_set_suspend_unlocked() themselves.
+ * Simple drivers might use drm_mode_config_helper_suspend().
+ *
+ * Returns:
+ * Zero on success or negative error code on failure.
+ */
+int drm_fbdev_generic_setup(struct drm_device *dev, unsigned int preferred_bpp)
+{
+	struct drm_fb_helper *fb_helper;
+	struct drm_client_dev *client;
+
+	if (!drm_fbdev_emulation)
+		return 0;
+
+	fb_helper = kzalloc(sizeof(*fb_helper), GFP_KERNEL);
+	if (!fb_helper)
+		return -ENOMEM;
+
+	client = drm_client_new(dev, &drm_fbdev_client_funcs);
+	if (IS_ERR(client)) {
+		kfree(fb_helper);
+		return PTR_ERR(client);
+	}
+
+	client->private = fb_helper;
+	fb_helper->client = client;
+	fb_helper->preferred_bpp = preferred_bpp;
+
+	drm_fbdev_client_hotplug(client);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_fbdev_generic_setup);
+
 /* The Kconfig DRM_KMS_HELPER selects FRAMEBUFFER_CONSOLE (if !EXPERT)
  * but the module doesn't depend on any fb console symbols.  At least
  * attempt to load fbcon to avoid leaving the system without a usable console.
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index 330983975d5e..711da1747836 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -126,6 +126,20 @@ struct drm_fb_helper {
 	 */
 	struct drm_client_display *display;
 
+	/**
+	 * @client:
+	 *
+	 * DRM client used by the generic fbdev emulation.
+	 */
+	struct drm_client_dev *client;
+
+	/**
+	 * @buffer:
+	 *
+	 * Framebuffer used by the generic fbdev emulation.
+	 */
+	struct drm_client_buffer *buffer;
+
 	const struct drm_fb_helper_funcs *funcs;
 	struct fb_info *fbdev;
 	u32 pseudo_palette[17];
@@ -219,6 +233,7 @@ struct drm_fb_helper {
 	.fb_ioctl	= drm_fb_helper_ioctl
 
 #ifdef CONFIG_DRM_FBDEV_EMULATION
+int drm_fbdev_generic_setup(struct drm_device *dev, unsigned int preferred_bpp);
 void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
 			   const struct drm_fb_helper_funcs *funcs);
 int drm_fb_helper_init(struct drm_device *dev,
@@ -297,6 +312,11 @@ void drm_fb_helper_fbdev_teardown(struct drm_device *dev);
 void drm_fb_helper_lastclose(struct drm_device *dev);
 void drm_fb_helper_output_poll_changed(struct drm_device *dev);
 #else
+static inline int
+drm_fbdev_generic_setup(struct drm_device *dev, unsigned int preferred_bpp)
+{
+}
+
 static inline void drm_fb_helper_prepare(struct drm_device *dev,
 					struct drm_fb_helper *helper,
 					const struct drm_fb_helper_funcs *funcs)
-- 
2.15.1

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