From 55bcdf37342d782c723166de54ff031d09b1281f Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Wed, 15 Oct 2025 19:32:21 -0700
Subject: Clear framebuffer to pink

---
 src/mailbox.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

(limited to 'src/mailbox.c')

diff --git a/src/mailbox.c b/src/mailbox.c
index 310b2b1..fcad179 100644
--- a/src/mailbox.c
+++ b/src/mailbox.c
@@ -7,7 +7,9 @@
 
 enum
 {
-  MAILBOX = 0xB880 // Mailbox address relative to MMIO base address.
+  MAILBOX      = 0xB880,     // Mailbox address relative to MMIO base address.
+  STATUS_EMPTY = 0x40000000, // Empty bit.
+  STATUS_FULL  = 0x80000000, // Full bit.
 };
 
 typedef uint32_t Message;
@@ -21,7 +23,7 @@ static inline Message msg_make(uint8_t channel, volatile const void* data) {
 }
 
 typedef struct Mailbox {
-  Message inbox;     // 0x00
+  Message  inbox;    // 0x00
   uint32_t unused_1; // 0x04
   uint32_t unused_2; // 0x08
   uint32_t unused_3; // 0x0C
@@ -29,15 +31,15 @@ typedef struct Mailbox {
   uint32_t unused_5; // 0x14
   uint32_t status;   // 0x18
   uint32_t unused_6; // 0x1C
-  Message outbox;    // 0x20
+  Message  outbox;   // 0x20
 } Mailbox;
 
 static inline bool inbox_empty(const volatile Mailbox* pMailbox) {
-  return (pMailbox->status & 0x40000000) != 0;
+  return (pMailbox->status & STATUS_EMPTY) != 0;
 }
 
 static inline bool outbox_full(const volatile Mailbox* pMailbox) {
-  return (pMailbox->status & 0x80000000) != 0;
+  return (pMailbox->status & STATUS_FULL) != 0;
 }
 
 static volatile Mailbox* pMailbox;
@@ -59,10 +61,15 @@ const Mail* mbox_read(uint8_t channel) {
   return (const Mail*)((uintptr_t)msg & ~0xf);
 }
 
-void mbox_write(uint8_t channel, volatile const void* mail) {
+uint32_t mbox_write(uint8_t channel, volatile const void* mail) {
   // Wait until the outbox is clear.
   while (outbox_full(pMailbox));
   // Send the mail.
   pMailbox->outbox = msg_make(channel, mail);
+  // Wait for the response.
+  // Mailbox messages cannot be streamed anyway, so wait here so that the API
+  // does not allow the caller to write two messages in a row without waiting.
+  const Mail* response = mbox_read(channel);
+  return response->code;
 }
 
-- 
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