An example to showcase the client API.

TODO:
A bootsplash client needs a way to tell drm_fb_helper to stay away,
otherwise it will chime in on setup and hotplug.
Most DRM drivers register fbdev before calling drm_dev_register() (the
generic emulation is an exception). This have to be reversed for
bootsplash to fend off fbdev.

Signed-off-by: Noralf Trønnes <nor...@tronnes.org>
---
 drivers/gpu/drm/Kconfig          |   5 +
 drivers/gpu/drm/Makefile         |   1 +
 drivers/gpu/drm/drm_bootsplash.c | 216 +++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_client.c     |   7 +
 drivers/gpu/drm/drm_drv.c        |   4 +
 include/drm/drm_client.h         |   3 +
 6 files changed, 236 insertions(+)
 create mode 100644 drivers/gpu/drm/drm_bootsplash.c

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 5e1bc630b885..a7019c54e2a2 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -65,6 +65,11 @@ config DRM_DEBUG_SELFTEST
 
          If in doubt, say "N".
 
+config DRM_CLIENT_BOOTSPLASH
+       bool "DRM Bootsplash"
+       help
+         DRM Bootsplash
+
 config DRM_KMS_HELPER
        tristate
        depends on DRM
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index e630eccb951c..ac0573023842 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -32,6 +32,7 @@ drm-$(CONFIG_OF) += drm_of.o
 drm-$(CONFIG_AGP) += drm_agpsupport.o
 drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o
 drm-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
+drm-$(CONFIG_DRM_CLIENT_BOOTSPLASH) += drm_bootsplash.o
 
 drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_dsc.o 
drm_probe_helper.o \
                drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
diff --git a/drivers/gpu/drm/drm_bootsplash.c b/drivers/gpu/drm/drm_bootsplash.c
new file mode 100644
index 000000000000..fdc3349a2496
--- /dev/null
+++ b/drivers/gpu/drm/drm_bootsplash.c
@@ -0,0 +1,216 @@
+/* DRM internal client example */
+
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/keyboard.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+#include <drm/drm_client.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fb_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_modes.h>
+#include <drm/drm_print.h>
+
+// drm_lastclose()
+#include "drm_internal.h"
+
+static bool drm_bootsplash_enabled = true;
+module_param_named(bootsplash_enabled, drm_bootsplash_enabled, bool, 0600);
+MODULE_PARM_DESC(bootsplash_enabled, "Enable bootsplash client 
[default=true]");
+
+struct drm_bootsplash {
+       struct drm_client_dev client;
+       struct mutex lock;
+       struct work_struct worker;
+       bool started;
+       bool stop;
+};
+
+static bool drm_bootsplash_key_pressed;
+
+static int drm_bootsplash_keyboard_notifier_call(struct notifier_block *blk,
+                                                unsigned long code, void 
*_param)
+{
+       /* Any key is good */
+       drm_bootsplash_key_pressed = true;
+
+       return NOTIFY_OK;
+}
+
+static struct notifier_block drm_bootsplash_keyboard_notifier_block = {
+       .notifier_call = drm_bootsplash_keyboard_notifier_call,
+};
+
+static u32 drm_bootsplash_color_table[3] = {
+       0x00ff0000, 0x0000ff00, 0x000000ff,
+};
+
+/* Draw a box with changing colors */
+static void drm_bootsplash_draw(struct drm_client_buffer *buffer, unsigned int 
sequence)
+{
+       unsigned int width = buffer->fb->width;
+       unsigned int height = buffer->fb->height;
+       unsigned int x, y;
+       u32 *pix;
+
+       pix = buffer->vaddr;
+       pix += ((height / 2) - 50) * width;
+       pix += (width / 2) - 50;
+
+       for (y = 0; y < 100; y++) {
+               for (x = 0; x < 100; x++)
+                       *pix++ = drm_bootsplash_color_table[sequence];
+               pix += width - 100;
+       }
+}
+
+static void drm_bootsplash_worker(struct work_struct *work)
+{
+       struct drm_bootsplash *splash = container_of(work, struct 
drm_bootsplash, worker);
+       struct drm_client_dev *client = &splash->client;
+       struct drm_device *dev = client->dev;
+       struct drm_client_display *display;
+       unsigned int buffer_num = 0, sequence = 0, i;
+       bool stop;
+       int ret = 0;
+
+       while (!drm_bootsplash_key_pressed) {
+               mutex_lock(&splash->lock);
+               stop = splash->stop;
+               mutex_unlock(&splash->lock);
+               if (stop)
+                       break;
+
+               buffer_num = !buffer_num;
+
+               mutex_lock(&client->displaylist_mutex);
+
+               ret = -ENOENT;
+
+               i = 0;
+               drm_client_for_each_display(display, client) {
+                       DRM_DEBUG_KMS("draw: i=%u, buffer_num=%u, 
sequence=%u\n", i++, buffer_num, sequence);
+
+                       drm_bootsplash_draw(display->buffers[buffer_num], 
sequence);
+
+                       ret = drm_client_display_commit_buffer(display, 
buffer_num);
+                       if (ret == -EBUSY)
+                               break;
+
+               }
+               mutex_unlock(&client->displaylist_mutex);
+
+               if (ret == -ENOENT || ret == -EBUSY)
+                       break;
+
+               if (++sequence == 3)
+                       sequence = 0;
+
+               msleep(500);
+       }
+
+       /* Restore fbdev (or other) on key press. */
+       /* TODO: Check if it's OK to call drm_lastclose here. */
+       if (drm_bootsplash_key_pressed && !splash->stop)
+               drm_lastclose(dev);
+
+       drm_client_release_displays(client);
+
+       DRM_DEV_DEBUG_KMS(dev->dev, "Bootsplash has stopped (key=%u stop=%u, 
ret=%d).\n",
+                         drm_bootsplash_key_pressed, splash->stop, ret);
+}
+
+static int drm_bootsplash_client_hotplug(struct drm_client_dev *client)
+{
+       struct drm_bootsplash *splash = container_of(client, struct 
drm_bootsplash, client);
+       int ret;
+
+       if (drm_bootsplash_key_pressed)
+               return 0;
+
+       mutex_lock(&splash->lock);
+
+       ret = drm_client_probe_displays(client, 2, DRM_FORMAT_XRGB8888);
+       if (!ret)
+               ret = -ENOENT;
+       if (ret < 0)
+               goto out_unlock;
+
+       /*
+        * TODO: Deal with rotated panels, might have to sw rotate
+       if (drm_client_panel_rotation(...))
+        */
+
+       if (!splash->started) {
+               splash->started = true;
+               schedule_work(&splash->worker);
+       }
+
+out_unlock:
+       mutex_unlock(&splash->lock);
+
+       return ret;
+}
+
+static void drm_bootsplash_client_unregister(struct drm_client_dev *client)
+{
+       struct drm_bootsplash *splash = container_of(client, struct 
drm_bootsplash, client);
+
+       DRM_DEBUG_KMS("%s: IN\n", __func__);
+
+       mutex_lock(&splash->lock);
+       splash->stop = true;
+       mutex_unlock(&splash->lock);
+
+       flush_work(&splash->worker);
+
+       drm_client_release(client);
+       kfree(splash);
+
+       unregister_keyboard_notifier(&drm_bootsplash_keyboard_notifier_block);
+
+       DRM_DEBUG_KMS("%s: OUT\n", __func__);
+}
+
+static const struct drm_client_funcs drm_bootsplash_client_funcs = {
+       .owner          = THIS_MODULE,
+       .unregister     = drm_bootsplash_client_unregister,
+       .hotplug        = drm_bootsplash_client_hotplug,
+};
+
+void drm_bootsplash_client_register(struct drm_device *dev)
+{
+       struct drm_bootsplash *splash;
+       int ret;
+
+       if (!drm_bootsplash_enabled)
+               return;
+
+       splash = kzalloc(sizeof(*splash), GFP_KERNEL);
+       if (!splash)
+               return;
+
+       ret = drm_client_init(dev, &splash->client, "bootsplash", 
&drm_bootsplash_client_funcs);
+       if (ret) {
+               DRM_DEV_ERROR(dev->dev, "Failed to create client, ret=%d\n", 
ret);
+               kfree(splash);
+               return;
+       }
+
+       /* For this simple example only allow the first */
+       drm_bootsplash_enabled = false;
+
+       mutex_init(&splash->lock);
+
+       INIT_WORK(&splash->worker, drm_bootsplash_worker);
+
+       drm_client_add(&splash->client);
+
+       register_keyboard_notifier(&drm_bootsplash_keyboard_notifier_block);
+
+       drm_bootsplash_client_hotplug(&splash->client);
+}
diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
index ef01a31a9dbe..b7458fac0863 100644
--- a/drivers/gpu/drm/drm_client.c
+++ b/drivers/gpu/drm/drm_client.c
@@ -170,6 +170,13 @@ void drm_client_release(struct drm_client_dev *client)
 }
 EXPORT_SYMBOL(drm_client_release);
 
+void drm_client_dev_register(struct drm_device *dev)
+{
+#if CONFIG_DRM_CLIENT_BOOTSPLASH
+       drm_bootsplash_client_register(dev);
+#endif
+}
+
 void drm_client_dev_unregister(struct drm_device *dev)
 {
        struct drm_client_dev *client, *tmp;
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 50d849d1bc6e..fbbb5f998baf 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -1018,6 +1018,10 @@ int drm_dev_register(struct drm_device *dev, unsigned 
long flags)
        drm_minor_unregister(dev, DRM_MINOR_RENDER);
 out_unlock:
        mutex_unlock(&drm_global_mutex);
+
+       if (!ret)
+               drm_client_dev_register(dev);
+
        return ret;
 }
 EXPORT_SYMBOL(drm_dev_register);
diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
index ef7a9bd07b3c..cabd3055ba8a 100644
--- a/include/drm/drm_client.h
+++ b/include/drm/drm_client.h
@@ -130,6 +130,7 @@ int drm_client_init(struct drm_device *dev, struct 
drm_client_dev *client,
 void drm_client_release(struct drm_client_dev *client);
 void drm_client_add(struct drm_client_dev *client);
 
+void drm_client_dev_register(struct drm_device *dev);
 void drm_client_dev_unregister(struct drm_device *dev);
 void drm_client_dev_hotplug(struct drm_device *dev);
 void drm_client_dev_restore(struct drm_device *dev);
@@ -251,4 +252,6 @@ int drm_client_display_commit_buffer(struct 
drm_client_display *display, unsigne
 
 int drm_client_debugfs_init(struct drm_minor *minor);
 
+void drm_bootsplash_client_register(struct drm_device *dev);
+
 #endif
-- 
2.20.1

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