From 31f06ea7c899c7b016fb1d20d9fcede9def7b63f Mon Sep 17 00:00:00 2001
From: Martin Whitaker <memtest@martin-whitaker.me.uk>
Date: Wed, 13 Apr 2022 14:30:52 +0100
Subject: [PATCH] Add a framebuffer test when EFI debug is enabled.

---
 boot/efisetup.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/boot/efisetup.c b/boot/efisetup.c
index 3e52eef..6effe8a 100644
--- a/boot/efisetup.c
+++ b/boot/efisetup.c
@@ -124,6 +124,48 @@ static void wait_for_key(void)
 
     while (efi_call_proto(efi_table_attr(sys_table, con_in), read_key_stroke, &input_key) == EFI_NOT_READY) {}
 }
+
+static void test_frame_buffer(screen_info_t *si)
+{
+    uint32_t r_value = 0xffffffff >> (32 - si->red_size);
+    uint32_t g_value = 0;
+    uint32_t b_value = 0;
+
+    int pixel_size = (si->lfb_depth / 8);
+
+    union {
+        uint8_t     byte[4];
+        uint32_t    word;
+    } pixel_value;
+
+    pixel_value.word = (r_value << si->red_pos) | (g_value << si->green_pos) | (b_value << si->blue_pos);
+
+    uintptr_t lfb_base = si->lfb_base;
+#ifdef __x86_64__
+    if (LFB_CAPABILITY_64BIT_BASE & si->capabilities) {
+        lfb_base |= (uintptr_t)si->ext_lfb_base << 32;
+    }
+#endif
+
+    uint8_t *lfb_row = (uint8_t *)lfb_base;
+    for (int y = 0; y < 8; y++) {
+        for (int x = 0; x < si->lfb_width; x++) {
+            for (int b = 0; b < pixel_size; b++) {
+                lfb_row[x * pixel_size + b] = pixel_value.byte[b];
+            }
+        }
+        lfb_row += si->lfb_linelength;
+    }
+    lfb_row += (si->lfb_height - 16) * si->lfb_linelength;
+    for (int y = 0; y < 8; y++) {
+        for (int x = 0; x < si->lfb_width; x++) {
+            for (int b = 0; b < pixel_size; b++) {
+                lfb_row[x * pixel_size + b] = pixel_value.byte[b];
+            }
+        }
+        lfb_row += si->lfb_linelength;
+    }
+}
 #endif
 
 static efi_memory_desc_t *get_memory_desc(uintptr_t map_addr, size_t desc_size, size_t n)
@@ -449,6 +491,12 @@ static efi_status_t set_screen_info_from_gop(screen_info_t *si, efi_handle_t *ha
         return status;
     }
 
+#if DEBUG
+    test_frame_buffer(si);
+    print_string("Press any key to continue...\n");
+    wait_for_key();
+#endif
+
     return EFI_SUCCESS;
 }