From: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date: Fri, 2 Feb 2018 15:27:43 +0100
Subject: drm/crc: Add support for polling on the data fd.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Git-commit: 4beb3b40ae7f994af01200323441df13f8f5b241
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

This will make it possible for userspace to know whether reading
will block, without blocking on the fd. This makes it possible to
drain all queued CRC's in blocking mode, without having to reopen
the fd.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180202142743.68527-1-maarten.lankhorst@linux.intel.com
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[mlankhorst: Use POLLIN|POLLRDNORM, based on Ville's suggestion]

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/drm_debugfs_crc.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

--- a/drivers/gpu/drm/drm_debugfs_crc.c
+++ b/drivers/gpu/drm/drm_debugfs_crc.c
@@ -307,10 +307,29 @@ static ssize_t crtc_crc_read(struct file
 	return LINE_LEN(crc->values_cnt);
 }
 
+static unsigned int crtc_crc_poll(struct file *file, poll_table *wait)
+{
+	struct drm_crtc *crtc = file->f_inode->i_private;
+	struct drm_crtc_crc *crc = &crtc->crc;
+	unsigned ret;
+
+	poll_wait(file, &crc->wq, wait);
+
+	spin_lock_irq(&crc->lock);
+	if (crc->source && crtc_crc_data_count(crc))
+		ret = POLLIN | POLLRDNORM;
+	else
+		ret = 0;
+	spin_unlock_irq(&crc->lock);
+
+	return ret;
+}
+
 static const struct file_operations drm_crtc_crc_data_fops = {
 	.owner = THIS_MODULE,
 	.open = crtc_crc_open,
 	.read = crtc_crc_read,
+	.poll = crtc_crc_poll,
 	.release = crtc_crc_release,
 };