[PATCH i-g-t 5/6] lib/igt_kms: Add helper to get eDP/DP supported link rates

[Jeevan B <jeevan.b@intel.com>]

Add igt_get_supported_link_rates to parse debugfs and return available
eDP/DP link rates for a given connector.

Signed-off-by: Jeevan B <jeevan.b@intel.com>
---
 lib/igt_kms.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_kms.h |  2 ++
 2 files changed, 54 insertions(+)

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index c03cfed09..4071aa00a 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -7632,3 +7632,55 @@ bool igt_has_lobf_debugfs(int drmfd, igt_output_t *output)
                                               buf, sizeof(buf));
         return res == 0;
 }
+
+/**
+ * igt_get_supported_link_rates:
+ * @drmfd: A drm file descriptor
+ * @connector_name: Name of the libdrm connector we're going to use
+ *
+ * Returns: All the link rates supported by the connector
+ */
+int igt_get_supported_link_rates(int drmfd, char *connector_name,
+		       int *rates, int max_rates)
+{
+	char buf[48];
+	int fd, res;
+	int count = 0;
+	char *token, *star;
+
+	if (!rates || max_rates <= 0) {
+		return -1;
+        }
+
+	fd = igt_debugfs_connector_dir(drmfd, connector_name, O_RDONLY);
+	igt_assert_lte(0, fd);
+
+	res = igt_debugfs_simple_read(fd, "i915_dp_force_link_rate", buf, sizeof(buf));
+	igt_require(res > 0);
+
+	igt_require_f(res > 0,
+		      "Unable to read i915_dp_force_link_rate for %s\n",
+		      connector_name);
+
+	buf[res] = '\0'; /* Null terminate */
+	token = strtok(buf, " \t\n");
+
+	while (token && count < max_rates) {
+		if (!strcmp(token, "[auto]")) {
+			token = strtok(NULL, " \t\n");
+			continue;
+		}
+
+		star = strchr(token, '*');
+		if (star)
+			*star = '\0';
+
+		if (isdigit(token[0])) {
+			rates[count++] = atoi(token);
+		}
+
+		token = strtok(NULL, " \t\n");
+	}
+
+	return count;
+}
diff --git a/lib/igt_kms.h b/lib/igt_kms.h
index cd9f6840a..474a809ea 100644
--- a/lib/igt_kms.h
+++ b/lib/igt_kms.h
@@ -1303,6 +1303,8 @@ void igt_set_link_params(int drm_fd, igt_output_t *output,
 int igt_backlight_read(int *result, const char *fname, igt_backlight_context_t *context);
 int igt_backlight_write(int value, const char *fname, igt_backlight_context_t *context);
 uint32_t igt_get_connected_output_count(igt_display_t *display);
+int igt_get_supported_link_rates(int drmfd, char *connector_name, int *rates,
+				 int max_rates);
 
 drmModePropertyBlobRes *igt_get_writeback_formats_blob(igt_output_t *output);
 
-- 
2.43.0