[PATCH 3/3] drm/i915/bios: abstract child device expected size

[Jani Nikula <jani.nikula@intel.com>]

Add a function to return the expected child device size. Flip the if
ladder around and use the same versions as in documentation to make it
easier to verify. Return an error for unknown versions. No functional
changes.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_bios.c | 37 ++++++++++++++---------
 1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index 9a51ab0d244e..25dde432212d 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -2695,25 +2695,32 @@ static void parse_ddi_ports(struct drm_i915_private *i915)
 		print_ddi_port(devdata);
 }
 
+static int child_device_expected_size(u16 version)
+{
+	if (version > 256)
+		return -ENOENT;
+	else if (version >= 256)
+		return 40;
+	else if (version >= 216)
+		return 39;
+	else if (version >= 196)
+		return 38;
+	else if (version >= 195)
+		return 37;
+	else if (version >= 111)
+		return LEGACY_CHILD_DEVICE_CONFIG_SIZE;
+	else if (version >= 106)
+		return 27;
+	else
+		return 22;
+}
+
 static bool child_device_size_valid(struct drm_i915_private *i915, int size)
 {
 	int expected_size;
 
-	if (i915->display.vbt.version < 106) {
-		expected_size = 22;
-	} else if (i915->display.vbt.version < 111) {
-		expected_size = 27;
-	} else if (i915->display.vbt.version < 195) {
-		expected_size = LEGACY_CHILD_DEVICE_CONFIG_SIZE;
-	} else if (i915->display.vbt.version == 195) {
-		expected_size = 37;
-	} else if (i915->display.vbt.version <= 215) {
-		expected_size = 38;
-	} else if (i915->display.vbt.version <= 255) {
-		expected_size = 39;
-	} else if (i915->display.vbt.version <= 256) {
-		expected_size = 40;
-	} else {
+	expected_size = child_device_expected_size(i915->display.vbt.version);
+	if (expected_size < 0) {
 		expected_size = sizeof(struct child_device_config);
 		BUILD_BUG_ON(sizeof(struct child_device_config) < 39);
 		drm_dbg(&i915->drm,
-- 
2.39.2