fix: report Adreno 840v2 as the A840 the runtime's Turnip knows

tools/linuxfs/preload/kgslid.c

@@ -0,0 +1,58 @@
+/*
+ * Adreno revisions the runtime's Turnip does not know, reported as the revision it does.
+ *
+ * Retail SM8850 phones report their A840 as chip_id 0x44050A21 (KGSL gpu_model "Adreno840v2").
+ * Mesa only lists 0x44050A31, so the runtime's glibc Turnip refuses the device outright
+ * ("device (chip_id = 44050A21, gpu_id = 6860) is unsupported") and gamescope exits before Steam
+ * starts. Banners-Turnip fixes its own builds by registering the v2 id on the same A840 GPU info
+ * (patches/a840v2.py); answering KGSL's device-info query with the known id has the same effect
+ * on any Turnip in the session, including the one the runtime was built with. A driver that
+ * already knows the v2 id resolves the rewritten one to the same entry.
+ *
+ * Only the KGSL device-info property is touched. Its layout is the kernel's uapi (msm_kgsl.h).
+ */
+#define _GNU_SOURCE 1
+#include <stddef.h>
+#include <sys/ioctl.h>
+
+struct kgsl_devinfo {
+    unsigned int device_id;
+    unsigned int chip_id;
+    unsigned int mmu_enabled;
+    unsigned long gmem_gpubaseaddr;
+    unsigned int gpu_id;
+    size_t gmem_sizebytes;
+};
+
+struct kgsl_device_getproperty {
+    unsigned int type;
+    void *value;
+    size_t sizebytes;
+};
+
+#define KGSL_IOC_TYPE 0x09
+#define IOCTL_KGSL_DEVICE_GETPROPERTY _IOWR(KGSL_IOC_TYPE, 0x2, struct kgsl_device_getproperty)
+#define KGSL_PROP_DEVICE_INFO 0x1
+
+static const struct {
+    unsigned int reported;
+    unsigned int known;
+} CHIP_IDS[] = {
+    {0x44050A21, 0x44050A31}, /* Adreno 840v2 -> Adreno 840 */
+};
+
+void bl_kgsl_chip_id_fixup(unsigned long request, void *arg, int rc) {
+    if (rc != 0 || request != IOCTL_KGSL_DEVICE_GETPROPERTY || arg == NULL) return;
+    struct kgsl_device_getproperty *prop = arg;
+    if (prop->type != KGSL_PROP_DEVICE_INFO || prop->value == NULL
+        || prop->sizebytes < sizeof(struct kgsl_devinfo)) {
+        return;
+    }
+    struct kgsl_devinfo *info = prop->value;
+    for (size_t i = 0; i < sizeof(CHIP_IDS) / sizeof(CHIP_IDS[0]); i++) {
+        if (info->chip_id == CHIP_IDS[i].reported) {
+            info->chip_id = CHIP_IDS[i].known;
+            return;
+        }
+    }
+}

tools/linuxfs/preload/netif.c

@@ -349,6 +349,8 @@ static int is_link_query(unsigned long request) {
         || request == SIOCGIFBRDADDR;
 }
 
+void bl_kgsl_chip_id_fixup(unsigned long request, void *arg, int rc); /* kgslid.c */
+
 /* Every DRM and evdev call comes through here, so the lookup is done once. Two threads racing
  * to store it store the same pointer. */
 int ioctl(int fd, unsigned long request, ...) {
@@ -361,6 +363,7 @@ int ioctl(int fd, unsigned long request, ...) {
 
     if (real == NULL) real = (ioctl_fn) dlsym(RTLD_NEXT, "ioctl");
     int rc = real(fd, request, arg);
+    bl_kgsl_chip_id_fixup(request, arg, rc);
     if (arg == NULL || !is_link_query(request)) return rc;
     int saved = errno;
     if (answer_ifreq(request, (struct ifreq *) arg, rc)) return 0;