drm: crc: Introduce get_crc_sources callback

This patch introduce a callback function "get_crc_sources" which
will be called during read of control node. It is an optional
callback function and if driver implements this callback, driver
should return a constant pointer to an array of crc sources list
and update count according to the number of source in the list.

Changes Since V1: (Daniel)
 - return const pointer to an array of crc sources list
 - do validation of sources in CRC-core
Changes Since V2:
 - update commit message
 - update callback documentation
 - print one source name per line

Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Cc: dri-devel@lists.freedesktop.org
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180713135942.25061-3-mahesh1.kumar@intel.com

drivers/gpu/drm/drm_debugfs_crc.c

@@ -68,8 +68,29 @@ static int crc_control_show(struct seq_file *m, void *data)
 {
 	struct drm_crtc *crtc = m->private;
 
-	seq_printf(m, "%s\n", crtc->crc.source);
+	if (crtc->funcs->get_crc_sources) {
+		size_t count;
+		const char *const *sources = crtc->funcs->get_crc_sources(crtc,
+									&count);
+		size_t values_cnt;
+		int i;
+
+		if (count == 0 || !sources)
+			goto out;
+
+		for (i = 0; i < count; i++)
+			if (!crtc->funcs->verify_crc_source(crtc, sources[i],
+							    &values_cnt)) {
+				if (strcmp(sources[i], crtc->crc.source))
+					seq_printf(m, "%s\n", sources[i]);
+				else
+					seq_printf(m, "%s*\n", sources[i]);
+			}
+	}
+	return 0;
 
+out:
+	seq_printf(m, "%s*\n", crtc->crc.source);
 	return 0;
 }
 

include/drm/drm_crtc.h

@@ -762,6 +762,28 @@ struct drm_crtc_funcs {
 	 */
 	int (*verify_crc_source)(struct drm_crtc *crtc, const char *source,
 				 size_t *values_cnt);
+	/**
+	 * @get_crc_sources:
+	 *
+	 * Driver callback for getting a list of all the available sources for
+	 * CRC generation. This callback depends upon verify_crc_source, So
+	 * verify_crc_source callback should be implemented before implementing
+	 * this. Driver can pass full list of available crc sources, this
+	 * callback does the verification on each crc-source before passing it
+	 * to userspace.
+	 *
+	 * This callback is optional if the driver does not support exporting of
+	 * possible CRC sources list.
+	 *
+	 * RETURNS:
+	 *
+	 * a constant character pointer to the list of all the available CRC
+	 * sources. On failure driver should return NULL. count should be
+	 * updated with number of sources in list. if zero we don't process any
+	 * source from the list.
+	 */
+	const char *const *(*get_crc_sources)(struct drm_crtc *crtc,
+					      size_t *count);
 
 	/**
 	 * @atomic_print_state: