Adds a per-device debugfile "drm_crc_control" that allows selecting a
source for frame checksums in each CRTC that supports them.

The checksums for each subsequent frame can be read from the per-CRTC
file "drm_crtc_N_crc".

The code is taken from the i915 driver and other drivers can now provide
frame CRCs by implementing the set_crc_source callback in
drm_crtc_funcs.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso at collabora.com>
---

 drivers/gpu/drm/drm_crtc.c     |  28 ++-
 drivers/gpu/drm/drm_debugfs.c  | 506 ++++++++++++++++++++++++++++++++++++++++-
 drivers/gpu/drm/drm_internal.h |  10 +
 include/drm/drmP.h             |   5 +
 include/drm/drm_crtc.h         |  72 ++++++
 5 files changed, 611 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index e7c862bd2f19..4dae42b122d9 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -657,8 +657,8 @@ int drm_crtc_init_with_planes(struct drm_device *dev, 
struct drm_crtc *crtc,
                                       drm_num_crtcs(dev));
        }
        if (!crtc->name) {
-               drm_mode_object_unregister(dev, &crtc->base);
-               return -ENOMEM;
+               ret = -ENOMEM;
+               goto err_unregister;
        }

        crtc->base.properties = &crtc->properties;
@@ -673,12 +673,30 @@ int drm_crtc_init_with_planes(struct drm_device *dev, 
struct drm_crtc *crtc,
        if (cursor)
                cursor->possible_crtcs = 1 << drm_crtc_index(crtc);

+#ifdef CONFIG_DEBUG_FS
+       spin_lock_init(&crtc->crc.lock);
+       init_waitqueue_head(&crtc->crc.wq);
+       crtc->crc.debugfs_entries = kmalloc_array(DRM_MINOR_CNT,
+                                         sizeof(*crtc->crc.debugfs_entries),
+                                         GFP_KERNEL);
+
+       ret = drm_debugfs_crtc_add(crtc);
+       if (ret)
+               goto err_free_name;
+#endif
+
        if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
                drm_object_attach_property(&crtc->base, config->prop_active, 0);
                drm_object_attach_property(&crtc->base, config->prop_mode_id, 
0);
        }

        return 0;
+
+err_free_name:
+       kfree(crtc->name);
+err_unregister:
+       drm_mode_object_unregister(dev, &crtc->base);
+       return ret;
 }
 EXPORT_SYMBOL(drm_crtc_init_with_planes);

@@ -699,6 +717,12 @@ void drm_crtc_cleanup(struct drm_crtc *crtc)
         * the indices on the drm_crtc after us in the crtc_list.
         */

+#ifdef CONFIG_DEBUG_FS
+       drm_debugfs_crtc_remove(crtc);
+       kfree(crtc->crc.debugfs_entries);
+       kfree(crtc->crc.source);
+#endif
+
        kfree(crtc->gamma_store);
        crtc->gamma_store = NULL;

diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index fa10cef2ba37..cdc8836bc22a 100644
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -30,6 +30,8 @@
  * OTHER DEALINGS IN THE SOFTWARE.
  */

+#include <linux/circ_buf.h>
+#include <linux/ctype.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
@@ -127,6 +129,259 @@ fail:
 }
 EXPORT_SYMBOL(drm_debugfs_create_files);

+static int
+drm_add_fake_info_node(struct drm_minor *minor,
+                      struct dentry *ent,
+                      const void *key)
+{
+       struct drm_info_node *node;
+
+       node = kmalloc(sizeof(*node), GFP_KERNEL);
+       if (node == NULL) {
+               debugfs_remove(ent);
+               return -ENOMEM;
+       }
+
+       node->minor = minor;
+       node->dent = ent;
+       node->info_ent = (void *) key;
+
+       mutex_lock(&minor->debugfs_lock);
+       list_add(&node->list, &minor->debugfs_list);
+       mutex_unlock(&minor->debugfs_lock);
+
+       return 0;
+}
+
+static int crc_control_show(struct seq_file *m, void *data)
+{
+       struct drm_device *dev = m->private;
+       struct drm_crtc *crtc;
+
+       drm_for_each_crtc(crtc, dev)
+               seq_printf(m, "crtc %d %s\n", crtc->index,
+                          crtc->crc.source ? crtc->crc.source : "none");
+
+       return 0;
+}
+
+static int crc_control_open(struct inode *inode, struct file *file)
+{
+       struct drm_device *dev = inode->i_private;
+
+       return single_open(file, crc_control_show, dev);
+}
+
+static int crc_control_update_crtc(struct drm_crtc *crtc, const char *source)
+{
+       struct drm_crtc_crc *crc = &crtc->crc;
+       struct drm_crtc_crc_entry *entries;
+       int ret;
+
+       if (!strcmp(source, "none"))
+               source = NULL;
+
+       if (!crc->source && !source)
+               return 0;
+
+       if (crc->source && source && !strcmp(crc->source, source))
+               return 0;
+
+       /* Forbid changing the source without going back to "none". */
+       if (crc->source && source)
+               return -EINVAL;
+
+       if (!crtc->funcs->set_crc_source)
+               return -ENOTSUPP;
+
+       if (source) {
+               entries = kcalloc(DRM_CRTC_CRC_ENTRIES_NR,
+                                 sizeof(crc->entries[0]),
+                                 GFP_KERNEL);
+               if (!entries)
+                       return -ENOMEM;
+
+               spin_lock_irq(&crc->lock);
+               kfree(crc->entries);
+               crc->entries = entries;
+               crc->head = 0;
+               crc->tail = 0;
+               spin_unlock_irq(&crc->lock);
+       }
+
+       ret = crtc->funcs->set_crc_source(crtc, source);
+       if (ret)
+               return ret;
+
+       kfree(crc->source);
+       crc->source = source ? kstrdup(source, GFP_KERNEL) : NULL;
+
+       if (!source) {
+               spin_lock_irq(&crc->lock);
+               entries = crc->entries;
+               crc->entries = NULL;
+               crc->head = 0;
+               crc->tail = 0;
+               spin_unlock_irq(&crc->lock);
+
+               kfree(entries);
+       }
+
+       return 0;
+}
+
+static struct drm_crtc *crtc_from_index(struct drm_device *dev, int index)
+{
+       struct drm_crtc *crtc;
+       int i = 0;
+
+       drm_for_each_crtc(crtc, dev)
+               if (i++ == index)
+                       return crtc;
+
+       return NULL;
+}
+
+/*
+ * Parse CRC command strings:
+ *   command: wsp* object wsp+ (crtc | pipe) wsp+ source wsp*
+ *   object: ('crtc' | 'pipe')
+ *   crtc: (0 | 1 | 2 | ...)
+ *   pipe: (A | B | C)
+ *   source: (none | plane1 | plane2 | ...)
+ *   wsp: (#0x20 | #0x9 | #0xA)+
+ *
+ * eg.:
+ *  "crtc 0 plane1"  ->  Start CRC computations on plane1 of first CRTC
+ *  "crtc 0 none"    ->  Stop CRC
+ */
+static int crc_control_tokenize(char *buf, char *words[], int max_words)
+{
+       int n_words = 0;
+
+       while (*buf) {
+               char *end;
+
+               /* skip leading white space */
+               buf = skip_spaces(buf);
+               if (!*buf)
+                       break;  /* end of buffer */
+
+               /* find end of word */
+               for (end = buf; *end && !isspace(*end); end++)
+                       ;
+
+               if (n_words == max_words) {
+                       DRM_DEBUG_KMS("too many words, allowed <= %d\n",
+                                     max_words);
+                       return -EINVAL; /* ran out of words[] before bytes */
+               }
+
+               if (*end)
+                       *end++ = '\0';
+               words[n_words++] = buf;
+               buf = end;
+       }
+
+       return n_words;
+}
+
+static int crc_control_parse_crtc(const char *buf, unsigned int *crtc_index)
+{
+       const char letter = buf[0];
+
+       if (!kstrtouint(buf, 10, crtc_index))
+               return 0;
+
+       /* Backwards compatibility for Intel-style pipe letters */
+       if (letter < 'A' || letter > 'Z')
+               return -EINVAL;
+
+       *crtc_index = letter - 'A';
+
+       return 0;
+}
+
+static int crc_control_parse(struct drm_device *dev, char *buf, size_t len)
+{
+#define N_WORDS 3
+       int n_words;
+       char *words[N_WORDS];
+       unsigned int crtc_index;
+       struct drm_crtc *crtc;
+
+       n_words = crc_control_tokenize(buf, words, N_WORDS);
+       if (n_words != N_WORDS) {
+               DRM_DEBUG_KMS("tokenize failed, a command is %d words\n",
+                             N_WORDS);
+               return -EINVAL;
+       }
+
+       if (strcmp(words[0], "crtc") && strcmp(words[0], "pipe")) {
+               DRM_DEBUG_KMS("Invalid command %s\n", words[0]);
+               return -EINVAL;
+       }
+
+       if (crc_control_parse_crtc(words[1], &crtc_index) < 0) {
+               DRM_DEBUG_KMS("Invalid CRTC index: %s\n", words[1]);
+               return -EINVAL;
+       }
+
+       crtc = crtc_from_index(dev, crtc_index);
+       if (!crtc) {
+               DRM_DEBUG_KMS("Unknown CRTC index: %d\n", crtc_index);
+               return -EINVAL;
+       }
+
+       return crc_control_update_crtc(crtc, words[2]);
+}
+
+static ssize_t crc_control_write(struct file *file, const char __user *ubuf,
+                                size_t len, loff_t *offp)
+{
+       struct seq_file *m = file->private_data;
+       struct drm_device *dev = m->private;
+       char *tmpbuf;
+       int ret;
+
+       if (len == 0)
+               return 0;
+
+       if (len > PAGE_SIZE - 1) {
+               DRM_DEBUG_KMS("expected <%lu bytes into crtc crc control\n",
+                             PAGE_SIZE);
+               return -E2BIG;
+       }
+
+       tmpbuf = kmalloc(len + 1, GFP_KERNEL);
+       if (!tmpbuf)
+               return -ENOMEM;
+
+       if (copy_from_user(tmpbuf, ubuf, len)) {
+               ret = -EFAULT;
+               goto out;
+       }
+       tmpbuf[len] = '\0';
+
+       ret = crc_control_parse(dev, tmpbuf, len);
+out:
+       kfree(tmpbuf);
+       if (ret < 0)
+               return ret;
+
+       *offp += len;
+       return len;
+}
+
+const struct file_operations drm_crc_control_fops = {
+       .owner = THIS_MODULE,
+       .open = crc_control_open,
+       .read = seq_read,
+       .llseek = seq_lseek,
+       .release = single_release,
+       .write = crc_control_write
+};
+
 /**
  * Initialize the DRI debugfs filesystem for a device
  *
@@ -142,8 +397,9 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
                     struct dentry *root)
 {
        struct drm_device *dev = minor->dev;
+       struct dentry *ent;
        char name[64];
-       int ret;
+       int ret = 0;

        INIT_LIST_HEAD(&minor->debugfs_list);
        mutex_init(&minor->debugfs_lock);
@@ -157,10 +413,23 @@ int drm_debugfs_init(struct drm_minor *minor, int 
minor_id,
        ret = drm_debugfs_create_files(drm_debugfs_list, DRM_DEBUGFS_ENTRIES,
                                       minor->debugfs_root, minor);
        if (ret) {
-               debugfs_remove(minor->debugfs_root);
-               minor->debugfs_root = NULL;
                DRM_ERROR("Failed to create core drm debugfs files\n");
-               return ret;
+               goto error_remove_dir;
+       }
+
+       ent = debugfs_create_file("drm_crc_control", S_IRUGO | S_IWUSR,
+                                 minor->debugfs_root, dev,
+                                 &drm_crc_control_fops);
+       if (!ent) {
+               DRM_ERROR("Failed to create CRC control debugfs files\n");
+               ret = -ENOMEM;
+               goto error_remove_files;
+       }
+
+       ret = drm_add_fake_info_node(minor, ent, &drm_crc_control_fops);
+       if (ret) {
+               DRM_ERROR("Failed to create CRC control debugfs files\n");
+               goto error_remove_crc;
        }

        if (dev->driver->debugfs_init) {
@@ -171,7 +440,18 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
                        return ret;
                }
        }
+
        return 0;
+
+error_remove_crc:
+       debugfs_remove(ent);
+error_remove_files:
+       drm_debugfs_remove_files(drm_debugfs_list, DRM_DEBUGFS_ENTRIES, minor);
+error_remove_dir:
+       debugfs_remove(minor->debugfs_root);
+       minor->debugfs_root = NULL;
+
+       return ret;
 }


@@ -407,13 +687,223 @@ error:

 void drm_debugfs_connector_remove(struct drm_connector *connector)
 {
-       if (!connector->debugfs_entry)
-               return;
-
        debugfs_remove_recursive(connector->debugfs_entry);

        connector->debugfs_entry = NULL;
 }

-#endif /* CONFIG_DEBUG_FS */
+static int crtc_crc_open(struct inode *inode, struct file *filep)
+{
+       struct drm_crtc *crtc = inode->i_private;
+       struct drm_crtc_crc *crc = &crtc->crc;
+
+       spin_lock_irq(&crc->lock);
+
+       if (crc->opened) {
+               spin_unlock_irq(&crc->lock);
+               return -EBUSY;
+       }
+
+       crc->opened = true;
+
+       spin_unlock_irq(&crc->lock);
+
+       return 0;
+}
+
+static int crtc_crc_release(struct inode *inode, struct file *filep)
+{
+       struct drm_crtc *crtc = filep->f_inode->i_private;
+       struct drm_crtc_crc *crc = &crtc->crc;
+
+       spin_lock_irq(&crc->lock);
+       crc->opened = false;
+       spin_unlock_irq(&crc->lock);
+
+       return 0;
+}
+
+/* (6 fields, 8 chars each, space separated (5) + '\n') */
+#define CRC_LINE_LEN   (6 * 8 + 5 + 1)
+/* account for \'0' */
+#define CRC_BUFFER_LEN (CRC_LINE_LEN + 1)
+
+static int crtc_crc_data_count(struct drm_crtc_crc *crc)
+{
+       assert_spin_locked(&crc->lock);
+       return CIRC_CNT(crc->head, crc->tail,
+                       DRM_CRTC_CRC_ENTRIES_NR);
+}
+
+static ssize_t crtc_crc_read(struct file *filep, char __user *user_buf,
+                            size_t count, loff_t *pos)
+{
+       struct drm_crtc *crtc = filep->f_inode->i_private;
+       struct drm_crtc_crc *crc = &crtc->crc;
+       char buf[CRC_BUFFER_LEN];
+       int n_entries;
+       ssize_t bytes_read;
+
+       /*
+        * Don't allow user space to provide buffers not big enough to hold
+        * a line of data.
+        */
+       if (count < CRC_LINE_LEN)
+               return -EINVAL;
+
+       if (!crc->source)
+               return 0;
+
+       /* Nothing to read? */
+       spin_lock_irq(&crc->lock);
+       while (crtc_crc_data_count(crc) == 0) {
+               int ret;
+
+               if (filep->f_flags & O_NONBLOCK) {
+                       spin_unlock_irq(&crc->lock);
+                       return -EAGAIN;
+               }
+
+               ret = wait_event_interruptible_lock_irq(crc->wq,
+                               crtc_crc_data_count(crc), crc->lock);
+               if (ret) {
+                       spin_unlock_irq(&crc->lock);
+                       return ret;
+               }
+       }
+
+       /* We now have one or more entries to read */
+       n_entries = count / CRC_LINE_LEN;
+
+       bytes_read = 0;
+       while (n_entries > 0) {
+               struct drm_crtc_crc_entry *entry =
+                       &crc->entries[crc->tail];
+               int ret;
+
+               if (CIRC_CNT(crc->head, crc->tail, DRM_CRTC_CRC_ENTRIES_NR) < 1)
+                       break;
+
+               BUILD_BUG_ON_NOT_POWER_OF_2(DRM_CRTC_CRC_ENTRIES_NR);
+               crc->tail = (crc->tail + 1) & (DRM_CRTC_CRC_ENTRIES_NR - 1);
+
+               bytes_read += snprintf(buf, CRC_BUFFER_LEN,
+                                      "%8u %8x %8x %8x %8x %8x\n",
+                                      entry->frame, entry->crc[0],
+                                      entry->crc[1], entry->crc[2],
+                                      entry->crc[3], entry->crc[4]);
+
+               spin_unlock_irq(&crc->lock);
+
+               ret = copy_to_user(user_buf, buf, CRC_LINE_LEN);
+               if (ret == CRC_LINE_LEN)
+                       return -EFAULT;

+               user_buf += CRC_LINE_LEN;
+               n_entries--;
+
+               spin_lock_irq(&crc->lock);
+       }
+
+       spin_unlock_irq(&crc->lock);
+
+       return bytes_read;
+}
+
+const struct file_operations drm_crtc_crc_fops = {
+       .owner = THIS_MODULE,
+       .open = crtc_crc_open,
+       .read = crtc_crc_read,
+       .release = crtc_crc_release,
+};
+
+static int drm_debugfs_crtc_add_for_minor(struct drm_crtc *crtc,
+                                         struct drm_minor *minor)
+{
+       struct dentry *ent;
+       char *name;
+
+       if (!minor->debugfs_root)
+               return -1;
+
+       name = kasprintf(GFP_KERNEL, "drm_crtc_%d_crc", crtc->index);
+       if (!name)
+               return -ENOMEM;
+
+       ent = debugfs_create_file(name, S_IRUGO, minor->debugfs_root, crtc,
+                                 &drm_crtc_crc_fops);
+       kfree(name);
+       if (!ent)
+               return PTR_ERR(ent);
+
+       crtc->crc.debugfs_entries[minor->type] = ent;
+
+       return 0;
+}
+
+int drm_debugfs_crtc_add(struct drm_crtc *crtc)
+{
+       int ret;
+
+       ret = drm_debugfs_crtc_add_for_minor(crtc, crtc->dev->control);
+       if (ret)
+               return ret;
+
+       ret = drm_debugfs_crtc_add_for_minor(crtc, crtc->dev->primary);
+       if (ret)
+               return ret;
+
+       ret = drm_debugfs_crtc_add_for_minor(crtc, crtc->dev->render);
+       if (ret)
+               return ret;
+
+       return 0;
+}
+
+void drm_debugfs_crtc_remove(struct drm_crtc *crtc)
+{
+       int i;
+
+       for (i = 0; i < DRM_MINOR_CNT; i++) {
+               debugfs_remove_recursive(crtc->crc.debugfs_entries[i]);
+               crtc->crc.debugfs_entries[i] = NULL;
+       }
+}
+
+void drm_crtc_add_crc_entry(struct drm_crtc *crtc, uint32_t frame,
+                           uint32_t crc0, uint32_t crc1, uint32_t crc2,
+                           uint32_t crc3, uint32_t crc4)
+{
+       struct drm_crtc_crc *crc = &crtc->crc;
+       struct drm_crtc_crc_entry *entry;
+       int head, tail;
+
+       spin_lock(&crc->lock);
+
+       head = crc->head;
+       tail = crc->tail;
+
+       if (CIRC_SPACE(head, tail, DRM_CRTC_CRC_ENTRIES_NR) < 1) {
+               spin_unlock(&crc->lock);
+               DRM_ERROR("Overflow of CRC buffer, userspace reads too 
slow.\n");
+               return;
+       }
+
+       entry = &crc->entries[head];
+
+       entry->frame = frame;
+       entry->crc[0] = crc0;
+       entry->crc[1] = crc1;
+       entry->crc[2] = crc2;
+       entry->crc[3] = crc3;
+       entry->crc[4] = crc4;
+
+       head = (head + 1) & (DRM_CRTC_CRC_ENTRIES_NR - 1);
+       crc->head = head;
+
+       spin_unlock(&crc->lock);
+
+       wake_up_interruptible(&crc->wq);
+}
+
+#endif /* CONFIG_DEBUG_FS */
diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h
index 38401d406532..e5b124d937f5 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -100,6 +100,8 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id,
 int drm_debugfs_cleanup(struct drm_minor *minor);
 int drm_debugfs_connector_add(struct drm_connector *connector);
 void drm_debugfs_connector_remove(struct drm_connector *connector);
+int drm_debugfs_crtc_add(struct drm_crtc *crtc);
+void drm_debugfs_crtc_remove(struct drm_crtc *crtc);
 #else
 static inline int drm_debugfs_init(struct drm_minor *minor, int minor_id,
                                   struct dentry *root)
@@ -119,4 +121,12 @@ static inline int drm_debugfs_connector_add(struct 
drm_connector *connector)
 static inline void drm_debugfs_connector_remove(struct drm_connector 
*connector)
 {
 }
+
+static inline int drm_debugfs_crtc_add(struct drm_crtc *crtc)
+{
+       return 0;
+}
+static inline void drm_debugfs_crtc_remove(struct drm_crtc *crtc)
+{
+}
 #endif
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 084fd141e8bf..ec2f91c8b7cd 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1142,6 +1142,11 @@ static __inline__ bool drm_can_sleep(void)
        return true;
 }

+#if defined(CONFIG_DEBUG_FS)
+extern const struct file_operations drm_crc_control_fops;
+extern const struct file_operations drm_crtc_crc_fops;
+#endif
+
 /* helper for handling conditionals in various for_each macros */
 #define for_each_if(condition) if (!(condition)) {} else

diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index c2734979f164..141335a3c647 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -376,6 +376,22 @@ struct drm_crtc_state {
        struct drm_atomic_state *state;
 };

+struct drm_crtc_crc_entry {
+       uint32_t frame;
+       uint32_t crc[5];
+};
+
+#define DRM_CRTC_CRC_ENTRIES_NR        128
+struct drm_crtc_crc {
+       spinlock_t lock;
+       const char *source;
+       bool opened;            /* exclusive access to the result file */
+       struct drm_crtc_crc_entry *entries;
+       int head, tail;
+       wait_queue_head_t wq;
+       struct dentry **debugfs_entries;
+};
+
 /**
  * struct drm_crtc_funcs - control CRTCs for a given device
  *
@@ -704,6 +720,29 @@ struct drm_crtc_funcs {
                                   const struct drm_crtc_state *state,
                                   struct drm_property *property,
                                   uint64_t *val);
+
+       /**
+        * @set_crc_source:
+        *
+        * Changes the source of CRC checksums of frames at the request of
+        * userspace, typically for testing purposes. The sources available are
+        * specific of each driver and a %NULL value indicates that CRC
+        * generation is to be switched off.
+        *
+        * When CRC generation is enabled, the driver should call
+        * drm_crtc_add_crc_entry() at each frame, providing any information
+        * that characterizes the frame contents in the crcN arguments, as
+        * provided from the configured source. Drivers should accept a "auto"
+        * source name that will select a default source for this CRTC.
+        *
+        * This callback is optional if the driver does not support any CRC
+        * generation functionality.
+        *
+        * RETURNS:
+        *
+        * 0 on success or a negative error code on failure.
+        */
+       int (*set_crc_source)(struct drm_crtc *crtc, const char *source);
 };

 /**
@@ -817,6 +856,15 @@ struct drm_crtc {
         * context.
         */
        struct drm_modeset_acquire_ctx *acquire_ctx;
+
+#ifdef CONFIG_DEBUG_FS
+       /**
+        * @drm_crtc_crc:
+        *
+        * Configuration settings of CRC capture.
+        */
+       struct drm_crtc_crc crc;
+#endif
 };

 /**
@@ -2496,6 +2544,30 @@ static inline uint32_t drm_crtc_mask(struct drm_crtc 
*crtc)
        return 1 << drm_crtc_index(crtc);
 }

+/**
+ * drm_crtc_add_crc_entry - Add entry with CRC information for a frame
+ * @crtc: CRTC to which the frame belongs
+ * @frame: number of the frame characterized by the CRC data
+ * @crc0: piece of data about frame
+ * @crc1: piece of data about frame
+ * @crc2: piece of data about frame
+ * @crc3: piece of data about frame
+ * @crc4: piece of data about frame
+ *
+ * For each frame, the driver polls the source of CRCs for new data and calls
+ * this function to add them to the buffer from where userspace reads.
+ */
+#if defined(CONFIG_DEBUG_FS)
+void drm_crtc_add_crc_entry(struct drm_crtc *crtc, uint32_t frame,
+                           uint32_t crc0, uint32_t crc1, uint32_t crc2,
+                           uint32_t crc3, uint32_t crc4);
+#else
+static inline void drm_crtc_add_crc_entry(struct drm_crtc *crtc, uint32_t 
frame,
+                                         uint32_t crc0, uint32_t crc1,
+                                         uint32_t crc2, uint32_t crc3,
+                                         uint32_t crc4) {}
+#endif
+
 extern void drm_connector_ida_init(void);
 extern void drm_connector_ida_destroy(void);
 extern int drm_connector_init(struct drm_device *dev,
-- 
2.5.5

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