[Intel-gfx] [PATCH for v4.2] Revert "drm/i915: Allow parsing of variable size child device entries from VBT"

[Jani Nikula]

This reverts

commit 047fe6e6db9161e69271f56daaafdaf2add023b1
Author: David Weinehall <david.weinehall at linux.intel.com>
Date:   Tue Aug 4 16:55:52 2015 +0300

    drm/i915: Allow parsing of variable size child device entries from VBT

That commit is not valid for v4.2, however it will be valid for v4.3. It
was simply queued too early.

The referenced regressing commit is just fine until the size of struct
common_child_dev_config changes, and that won't happen until
v4.3. Indeed, the expected size checks here rely on the increased size
of the struct, breaking new platforms.

Fixes: 047fe6e6db91 ("drm/i915: Allow parsing of variable size child device entries from VBT")
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: David Weinehall <david.weinehall at linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula at intel.com>

---

There was another patch from David increasing the size of the struct
[1], but that then regresses sdvo mapping parsing. It's the simplest to
just revert and fix this up properly for v4.3.

[1] http://mid.gmane.org/20150813131415.GO6150@boom
---
 drivers/gpu/drm/i915/intel_bios.c | 27 ++++-----------------------
 1 file changed, 4 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 3dcd59e694db..198fc3c3291b 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -1075,34 +1075,15 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
 	const union child_device_config *p_child;
 	union child_device_config *child_dev_ptr;
 	int i, child_device_num, count;
-	u8 expected_size;
-	u16 block_size;
+	u16	block_size;
 
 	p_defs = find_section(bdb, BDB_GENERAL_DEFINITIONS);
 	if (!p_defs) {
 		DRM_DEBUG_KMS("No general definition block is found, no devices defined.\n");
 		return;
 	}
-	if (bdb->version < 195) {
-		expected_size = 33;
-	} else if (bdb->version == 195) {
-		expected_size = 37;
-	} else if (bdb->version <= 197) {
-		expected_size = 38;
-	} else {
-		expected_size = 38;
-		DRM_DEBUG_DRIVER("Expected child_device_config size for BDB version %u not known; assuming %u\n",
-				 expected_size, bdb->version);
-	}
-
-	if (expected_size > sizeof(*p_child)) {
-		DRM_ERROR("child_device_config cannot fit in p_child\n");
-		return;
-	}
-
-	if (p_defs->child_dev_size != expected_size) {
-		DRM_ERROR("Size mismatch; child_device_config size=%u (expected %u); bdb->version: %u\n",
-			  p_defs->child_dev_size, expected_size, bdb->version);
+	if (p_defs->child_dev_size < sizeof(*p_child)) {
+		DRM_ERROR("General definiton block child device size is too small.\n");
 		return;
 	}
 	/* get the block size of general definitions */
@@ -1149,7 +1130,7 @@ parse_device_mapping(struct drm_i915_private *dev_priv,
 
 		child_dev_ptr = dev_priv->vbt.child_dev + count;
 		count++;
-		memcpy(child_dev_ptr, p_child, p_defs->child_dev_size);
+		memcpy(child_dev_ptr, p_child, sizeof(*p_child));
 	}
 	return;
 }
-- 
2.1.4