This patch implements a callback function "pre_crc_read" which will
be called before crc read. In this function driver can implement and
preparation work required for successfully reading CRC data.

Signed-off-by: Mahesh Kumar <mahesh1.ku...@intel.com>
Cc: dri-devel@lists.freedesktop.org
---
 drivers/gpu/drm/drm_debugfs_crc.c |  8 ++++++++
 include/drm/drm_crtc.h            | 14 ++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/drm_debugfs_crc.c 
b/drivers/gpu/drm/drm_debugfs_crc.c
index c6a725b79ac6..2b4a737c5aeb 100644
--- a/drivers/gpu/drm/drm_debugfs_crc.c
+++ b/drivers/gpu/drm/drm_debugfs_crc.c
@@ -278,6 +278,14 @@ static ssize_t crtc_crc_read(struct file *filep, char 
__user *user_buf,
                return 0;
        }
 
+       if (crtc->funcs->pre_crc_read) {
+               ret = crtc->funcs->pre_crc_read(crtc);
+               if (ret) {
+                       spin_unlock_irq(&crc->lock);
+                       return ret;
+               }
+       }
+
        /* Nothing to read? */
        while (crtc_crc_data_count(crc) == 0) {
                if (filep->f_flags & O_NONBLOCK) {
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 1a6dcbf91744..bae432469616 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -676,6 +676,20 @@ struct drm_crtc_funcs {
         */
        int (*verify_crc_source)(struct drm_crtc *crtc, const char *source,
                                 size_t *values_cnt);
+       /**
+        * @pre_crc_read:
+        *
+        * Driver callback for performing any preparation work required by
+        * driver before reading CRC
+        *
+        * This callback is optional if the driver does not support CRC
+        * generation or no prework is required before reading the crc
+        *
+        * RETURNS:
+        *
+        * 0 on success or a negative error code on failure.
+        */
+       int (*pre_crc_read)(struct drm_crtc *crtc);
 
        /**
         * @atomic_print_state:
-- 
2.16.2

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