[plasma/kwin] src: utils/edid: fix hexadecimal strings in output names

Git commit 495d442585e255e7bb7f3e2d570ff2a881d53ce5 by Nate Graham, on behalf of David Wild.
Committed on 05/08/2026 at 15:09.
Pushed by ngraham into branch 'master'.

utils/edid: fix hexadecimal strings in output names

KWin uses libdisplay-info to decode EDID data. di_info_get_model() and
di_info_get_serial() fall back to hexadecimal values when no Display
Product Name or Serial Number descriptor is found.

This patch stops using those helpers and instead implements a direct
descriptor parser, similar to libkscreen's decoder: we still fall back
to a decimal value for the serial number,  but not for the model, so
m_monitorName is left empty if no name descriptor exists.

To avoid showing "unknown" when m_monitorName is empty,
DrmConnector::modelName() now skips empty values instead of
concatenating them (similar to libkscreen).

Note: if necessary a decimal fallback for the model (m_monitorName)
could be added later in the same way. Currently, the model falls back
to a hexadecimal representation,  but libkscreen has none either, so
this patch leaves it out for now.

BUG: 523181
FIXED-IN: 6.6.7

M  +3    -0    src/backends/drm/drm_connector.cpp
M  +19   -4    src/utils/edid.cpp

https://invent.kde.org/plasma/kwin/-/commit/495d442585e255e7bb7f3e2d570ff2a881d53ce5

diff --git a/src/backends/drm/drm_connector.cpp b/src/backends/drm/drm_connector.cpp
index 59d7ee52ca9..5c7122e135b 100644
--- a/src/backends/drm/drm_connector.cpp
+++ b/src/backends/drm/drm_connector.cpp
@@ -211,6 +211,9 @@ QString DrmConnector::connectorName() const
 
 QString DrmConnector::modelName() const
 {
+    if (m_edid.monitorName().isEmpty() && m_edid.serialNumber().isEmpty()) {
+        return connectorName(); // just use the connector name
+    }
     if (m_edid.serialNumber().isEmpty()) {
         return connectorName() + QLatin1Char('-') + m_edid.nameString();
     } else {
diff --git a/src/utils/edid.cpp b/src/utils/edid.cpp
index a2a0d11f362..8204a24ea99 100644
--- a/src/utils/edid.cpp
+++ b/src/utils/edid.cpp
@@ -77,6 +77,20 @@ static QByteArray parseEisaId(const uint8_t *data)
     return parsePnpId(data);
 }
 
+static QByteArray parseDescriptorString(const di_edid *edid, di_edid_display_descriptor_tag wantedTag)
+{
+    const di_edid_display_descriptor *const *descriptors = di_edid_get_display_descriptors(edid);
+    for (; *descriptors != nullptr; descriptors++) {
+        if (di_edid_display_descriptor_get_tag(*descriptors) != wantedTag) {
+            continue;
+        }
+        if (const char *str = di_edid_display_descriptor_get_string(*descriptors); str && str[0] != '\0') {
+            return QByteArray(str).trimmed();
+        }
+    }
+    return {};
+}
+
 static QByteArray parseVendor(const uint8_t *data)
 {
     const auto pnpId = parsePnpId(data);
@@ -167,10 +181,11 @@ Edid::Edid(QByteArrayView data)
     m_physicalSize = determineScreenPhysicalSizeMm(edid);
     m_eisaId = parseEisaId(bytes);
     m_pnpId = parsePnpId(bytes);
-    UniqueCPtr<char> monitorName{di_info_get_model(info)};
-    m_monitorName = QByteArray(monitorName.get());
-    UniqueCPtr<char> serial{di_info_get_serial(info)};
-    m_serialNumber = QByteArray(serial.get());
+    m_monitorName = parseDescriptorString(edid, DI_EDID_DISPLAY_DESCRIPTOR_PRODUCT_NAME);
+    m_serialNumber = parseDescriptorString(edid, DI_EDID_DISPLAY_DESCRIPTOR_PRODUCT_SERIAL);
+    if (m_serialNumber.isEmpty() && productInfo->serial != 0) {
+        m_serialNumber = QByteArray::number(productInfo->serial); // fallback to decimal value
+    }
     m_vendor = parseVendor(bytes);
 
     m_identifier = QByteArray(productInfo->manufacturer, 3) + " " + QByteArray::number(productInfo->product) + " " + QByteArray::number(productInfo->serial) + " "