[PATCH v2 04/12] drm: Begin an API for in-kernel clients

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

This the beginning of an API for in-kernel clients.
First out is a way to get a framebuffer backed by a dumb buffer.

Only GEM drivers are supported.
The original idea of using an exported dma-buf was dropped because it
also creates an anonomous file descriptor which doesn't work when the
buffer is created from a kernel thread. The easy way out is to use
drm_driver.gem_prime_vmap to get the virtual address, which requires a
GEM object. This excludes the vmwgfx driver which is the only non-GEM
driver apart from the legacy ones. A solution for vmwgfx will have to be
worked out later if it wants to support the client API which it probably
will when we have a bootsplash client.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---

Changes since version 1:
- Make it possible to embed struct drm_client_dev and drop the private
  pointer
- Use kref reference counting to control client release since both the
  client and the driver can release.
- Add comment about using dma-buf as a possibility with some rework
- Move buffer NULL check to drm_client_framebuffer_delete()
- Move client name to struct drm_client_dev
- Move up drm_dev_get/put calls to make them more visible
- Move drm_client_dev.list definition to later patch that makes use of it


 Documentation/gpu/drm-client.rst |  12 ++
 Documentation/gpu/index.rst      |   1 +
 drivers/gpu/drm/Makefile         |   2 +-
 drivers/gpu/drm/drm_client.c     | 316 +++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_drv.c        |   1 +
 include/drm/drm_client.h         |  87 +++++++++++
 include/drm/drm_device.h         |   7 +
 7 files changed, 425 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/gpu/drm-client.rst
 create mode 100644 drivers/gpu/drm/drm_client.c
 create mode 100644 include/drm/drm_client.h

diff --git a/Documentation/gpu/drm-client.rst b/Documentation/gpu/drm-client.rst
new file mode 100644
index 000000000000..7e672063e7eb
--- /dev/null
+++ b/Documentation/gpu/drm-client.rst
@@ -0,0 +1,12 @@
+=================
+Kernel clients
+=================
+
+.. kernel-doc:: drivers/gpu/drm/drm_client.c
+   :doc: overview
+
+.. kernel-doc:: include/drm/drm_client.h
+   :internal:
+
+.. kernel-doc:: drivers/gpu/drm/drm_client.c
+   :export:
diff --git a/Documentation/gpu/index.rst b/Documentation/gpu/index.rst
index 00288f34c5a6..1fcf8e851e15 100644
--- a/Documentation/gpu/index.rst
+++ b/Documentation/gpu/index.rst
@@ -10,6 +10,7 @@ Linux GPU Driver Developer's Guide
    drm-kms
    drm-kms-helpers
    drm-uapi
+   drm-client
    drivers
    vga-switcheroo
    vgaarbiter
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index ef9f3dab287f..8c8045147416 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -18,7 +18,7 @@ drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
 		drm_encoder.o drm_mode_object.o drm_property.o \
 		drm_plane.o drm_color_mgmt.o drm_print.o \
 		drm_dumb_buffers.o drm_mode_config.o drm_vblank.o \
-		drm_syncobj.o drm_lease.o
+		drm_syncobj.o drm_lease.o drm_client.o
 
 drm-$(CONFIG_DRM_LIB_RANDOM) += lib/drm_random.o
 drm-$(CONFIG_DRM_VM) += drm_vm.o
diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
new file mode 100644
index 000000000000..98dda40f5416
--- /dev/null
+++ b/drivers/gpu/drm/drm_client.c
@@ -0,0 +1,316 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018 Noralf Trønnes
+ */
+
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+
+#include <drm/drm_client.h>
+#include <drm/drm_debugfs.h>
+#include <drm/drm_device.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_file.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_mode.h>
+#include <drm/drm_print.h>
+#include <drm/drmP.h>
+
+#include "drm_crtc_internal.h"
+#include "drm_internal.h"
+
+/**
+ * DOC: overview
+ *
+ * This library provides support for clients running in the kernel like fbdev and bootsplash.
+ * Currently it's only partially implemented, just enough to support fbdev.
+ *
+ * GEM drivers which provide a GEM based dumb buffer with a virtual address are supported.
+ */
+
+static int drm_client_open(struct drm_client_dev *client)
+{
+	struct drm_device *dev = client->dev;
+	struct drm_file *file;
+
+	file = drm_file_alloc(dev->primary);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	mutex_lock(&dev->filelist_mutex);
+	list_add(&file->lhead, &dev->filelist_internal);
+	mutex_unlock(&dev->filelist_mutex);
+
+	client->file = file;
+
+	return 0;
+}
+
+/**
+ * drm_client_close - Close the client DRM file
+ * @client: DRM client
+ *
+ * Close the &drm_file that was opened by drm_client_new(). It is called
+ * automatically if the &drm_client_funcs.release callback is not set.
+ * This function should only be called from the release callback.
+ */
+void drm_client_close(struct drm_client_dev *client)
+{
+	struct drm_device *dev = client->dev;
+
+	mutex_lock(&dev->filelist_mutex);
+	list_del(&client->file->lhead);
+	mutex_unlock(&dev->filelist_mutex);
+
+	drm_file_free(client->file);
+}
+EXPORT_SYMBOL(drm_client_close);
+
+/**
+ * drm_client_new - Create a DRM client
+ * @dev: DRM device
+ * @client: DRM client
+ * @name: Client name
+ *
+ * Use drm_client_put() to free the client.
+ *
+ * Returns:
+ * Zero on success or negative error code on failure.
+ */
+int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
+		   const char *name)
+{
+	int ret;
+
+	if (!drm_core_check_feature(dev, DRIVER_MODESET) ||
+	    !dev->driver->dumb_create || !dev->driver->gem_prime_vmap)
+		return -ENOTSUPP;
+
+	client->dev = dev;
+	client->name = name;
+	kref_init(&client->ref);
+
+	ret = drm_client_open(client);
+	if (ret)
+		return ret;
+
+	drm_dev_get(dev);
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_client_new);
+
+static void drm_client_release(struct kref *ref)
+{
+	struct drm_client_dev *client = container_of(ref, struct drm_client_dev, ref);
+	struct drm_device *dev = client->dev;
+
+	DRM_DEV_DEBUG_KMS(dev->dev, "%s\n", client->name);
+
+	drm_client_close(client);
+	kfree(client);
+
+	drm_dev_put(dev);
+}
+
+/**
+ * drm_client_get - Take a reference of a DRM client
+ * @client: DRM client (can be NULL)
+ *
+ * This increases the ref-count of @client by one. You *must* already own a
+ * reference when calling this. Use drm_client_put() to drop this reference
+ * again.
+ */
+void drm_client_get(struct drm_client_dev *client)
+{
+	if (client)
+		kref_get(&client->ref);
+}
+EXPORT_SYMBOL(drm_client_get);
+
+/**
+ * drm_client_put - Drop reference of a DRM client
+ * @client: DRM client (can be NULL)
+ *
+ * This decreases the ref-count of @client by one. The client resources are
+ * released if the ref-count drops to zero.
+ */
+void drm_client_put(struct drm_client_dev *client)
+{
+	if (client)
+		kref_put(&client->ref, drm_client_release);
+}
+EXPORT_SYMBOL(drm_client_put);
+
+static void drm_client_buffer_delete(struct drm_client_buffer *buffer)
+{
+	struct drm_device *dev;
+
+	dev = buffer->client->dev;
+	if (buffer->vaddr && dev->driver->gem_prime_vunmap)
+		dev->driver->gem_prime_vunmap(buffer->gem, buffer->vaddr);
+
+	if (buffer->gem)
+		drm_gem_object_put_unlocked(buffer->gem);
+
+	drm_mode_destroy_dumb(dev, buffer->handle, buffer->client->file);
+	kfree(buffer);
+}
+
+static struct drm_client_buffer *
+drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u32 format)
+{
+	struct drm_mode_create_dumb dumb_args = { };
+	struct drm_device *dev = client->dev;
+	struct drm_client_buffer *buffer;
+	struct drm_gem_object *obj;
+	void *vaddr;
+	int ret;
+
+	buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
+	if (!buffer)
+		return ERR_PTR(-ENOMEM);
+
+	buffer->client = client;
+
+	dumb_args.width = width;
+	dumb_args.height = height;
+	dumb_args.bpp = drm_format_plane_cpp(format, 0) * 8;
+	ret = drm_mode_create_dumb(dev, &dumb_args, client->file);
+	if (ret)
+		goto err_free;
+
+	buffer->handle = dumb_args.handle;
+	buffer->pitch = dumb_args.pitch;
+
+	obj = drm_gem_object_lookup(client->file, dumb_args.handle);
+	if (!obj)  {
+		ret = -ENOENT;
+		goto err_delete;
+	}
+
+	buffer->gem = obj;
+
+	/*
+	 * FIXME: The dependency on GEM here isn't required, we could
+	 * convert the driver handle to a dma-buf instead and use the
+	 * backend-agnostic dma-buf vmap support instead. This would
+	 * require that the handle2fd prime ioctl is reworked to pull the
+	 * fd_install step out of the driver backend hooks, to make that
+	 * final step optional for internal users.
+	 */
+	vaddr = dev->driver->gem_prime_vmap(obj);
+	if (!vaddr) {
+		ret = -ENOMEM;
+		goto err_delete;
+	}
+
+	buffer->vaddr = vaddr;
+
+	return buffer;
+
+err_delete:
+	drm_client_buffer_delete(buffer);
+err_free:
+	kfree(buffer);
+
+	return ERR_PTR(ret);
+}
+
+static void drm_client_buffer_rmfb(struct drm_client_buffer *buffer)
+{
+	int ret;
+
+	if (!buffer->fb)
+		return;
+
+	ret = drm_mode_rmfb(buffer->client->dev, buffer->fb->base.id, buffer->client->file);
+	if (ret)
+		DRM_DEV_ERROR(buffer->client->dev->dev,
+			      "Error removing FB:%u (%d)\n", buffer->fb->base.id, ret);
+
+	buffer->fb = NULL;
+}
+
+static int drm_client_buffer_addfb(struct drm_client_buffer *buffer,
+				   u32 width, u32 height, u32 format)
+{
+	struct drm_client_dev *client = buffer->client;
+	struct drm_mode_fb_cmd fb_req = { };
+	const struct drm_format_info *info;
+	int ret;
+
+	info = drm_format_info(format);
+	fb_req.bpp = info->cpp[0] * 8;
+	fb_req.depth = info->depth;
+	fb_req.width = width;
+	fb_req.height = height;
+	fb_req.handle = buffer->handle;
+	fb_req.pitch = buffer->pitch;
+
+	ret = drm_mode_addfb(client->dev, &fb_req, client->file);
+	if (ret)
+		return ret;
+
+	buffer->fb = drm_framebuffer_lookup(client->dev, buffer->client->file, fb_req.fb_id);
+	if (WARN_ON(!buffer->fb))
+		return -ENOENT;
+
+	/* drop the reference we picked up in framebuffer lookup */
+	drm_framebuffer_put(buffer->fb);
+
+	strscpy(buffer->fb->comm, client->name, TASK_COMM_LEN);
+
+	return 0;
+}
+
+/**
+ * drm_client_framebuffer_create - Create a client framebuffer
+ * @client: DRM client
+ * @width: Framebuffer width
+ * @height: Framebuffer height
+ * @format: Buffer format
+ *
+ * This function creates a &drm_client_buffer which consists of a
+ * &drm_framebuffer backed by a dumb buffer.
+ * Call drm_client_framebuffer_delete() to free the buffer.
+ *
+ * Returns:
+ * Pointer to a client buffer or an error pointer on failure.
+ */
+struct drm_client_buffer *
+drm_client_framebuffer_create(struct drm_client_dev *client, u32 width, u32 height, u32 format)
+{
+	struct drm_client_buffer *buffer;
+	int ret;
+
+	buffer = drm_client_buffer_create(client, width, height, format);
+	if (IS_ERR(buffer))
+		return buffer;
+
+	ret = drm_client_buffer_addfb(buffer, width, height, format);
+	if (ret) {
+		drm_client_buffer_delete(buffer);
+		return ERR_PTR(ret);
+	}
+
+	return buffer;
+}
+EXPORT_SYMBOL(drm_client_framebuffer_create);
+
+/**
+ * drm_client_framebuffer_delete - Delete a client framebuffer
+ * @buffer: DRM client buffer (can be NULL)
+ */
+void drm_client_framebuffer_delete(struct drm_client_buffer *buffer)
+{
+	if (!buffer)
+		return;
+
+	drm_client_buffer_rmfb(buffer);
+	drm_client_buffer_delete(buffer);
+}
+EXPORT_SYMBOL(drm_client_framebuffer_delete);
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index f6910ebe4d0e..67ac793a7108 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -505,6 +505,7 @@ int drm_dev_init(struct drm_device *dev,
 	dev->driver = driver;
 
 	INIT_LIST_HEAD(&dev->filelist);
+	INIT_LIST_HEAD(&dev->filelist_internal);
 	INIT_LIST_HEAD(&dev->ctxlist);
 	INIT_LIST_HEAD(&dev->vmalist);
 	INIT_LIST_HEAD(&dev->maplist);
diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
new file mode 100644
index 000000000000..12ac2615b17d
--- /dev/null
+++ b/include/drm/drm_client.h
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _DRM_CLIENT_H_
+#define _DRM_CLIENT_H_
+
+#include <linux/kref.h>
+#include <linux/types.h>
+
+struct drm_device;
+struct drm_framebuffer;
+struct drm_gem_object;
+struct drm_minor;
+
+/**
+ * struct drm_client_dev - DRM client instance
+ */
+struct drm_client_dev {
+	/**
+	 * @dev: DRM device
+	 */
+	struct drm_device *dev;
+
+	/**
+	 * @name: Name of the client.
+	 */
+	const char *name;
+
+	/**
+	 * @ref:
+	 *
+	 * Reference counting. The client resources are released when this drops
+	 * to zero.
+	 */
+	struct kref ref;
+
+	/**
+	 * @file: DRM file
+	 */
+	struct drm_file *file;
+};
+
+void drm_client_close(struct drm_client_dev *client);
+int drm_client_new(struct drm_device *dev, struct drm_client_dev *client,
+		   const char *name);
+void drm_client_get(struct drm_client_dev *client);
+void drm_client_put(struct drm_client_dev *client);
+
+/**
+ * struct drm_client_buffer - DRM client buffer
+ */
+struct drm_client_buffer {
+	/**
+	 * @client: DRM client
+	 */
+	struct drm_client_dev *client;
+
+	/**
+	 * @handle: Buffer handle
+	 */
+	u32 handle;
+
+	/**
+	 * @pitch: Buffer pitch
+	 */
+	u32 pitch;
+
+	/**
+	 * @gem: GEM object backing this buffer
+	 */
+	struct drm_gem_object *gem;
+
+	/**
+	 * @vaddr: Virtual address for the buffer
+	 */
+	void *vaddr;
+
+	/**
+	 * @fb: DRM framebuffer
+	 */
+	struct drm_framebuffer *fb;
+};
+
+struct drm_client_buffer *
+drm_client_framebuffer_create(struct drm_client_dev *client, u32 width, u32 height, u32 format);
+void drm_client_framebuffer_delete(struct drm_client_buffer *buffer);
+
+#endif
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index 858ba19a3e29..9e29976d4e98 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -74,6 +74,13 @@ struct drm_device {
 	struct mutex filelist_mutex;
 	struct list_head filelist;
 
+	/**
+	 * @filelist_internal:
+	 *
+	 * List of open DRM files for in-kernel clients. Protected by @filelist_mutex.
+	 */
+	struct list_head filelist_internal;
+
 	/** \name Memory management */
 	/*@{ */
 	struct list_head maplist;	/**< Linked list of regions */
-- 
2.15.1

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