[PATCH V2 4/4] drm/crc: add pre_crc_read function

[Mahesh Kumar <mahesh1.kumar@intel.com>]

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

Changes Since V1:
 - rebase

Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
---
 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 00e743153e94..e303c194c080 100644
--- a/drivers/gpu/drm/drm_debugfs_crc.c
+++ b/drivers/gpu/drm/drm_debugfs_crc.c
@@ -274,6 +274,14 @@ 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 b21437bc95bf..19c2bf63935e 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -761,6 +761,20 @@ 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);
 	/**
 	 * @get_crc_sources:
 	 *
-- 
2.16.2

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