From 363eea1f6ea7fc0859be8c0bb5c3925e69ca31eb Mon Sep 17 00:00:00 2001
From: Malo Lecomte <malo.lecomte@epita.fr>
Date: Mon, 26 Jul 2021 14:55:13 +0200
Subject: [PATCH] feat(atapi): add drive discover functions

---
 k/atapi.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 k/atapi.h | 14 +++++++++++
 2 files changed, 89 insertions(+)
 create mode 100644 k/atapi.c
 create mode 100644 k/atapi.h

diff --git a/k/atapi.c b/k/atapi.c
new file mode 100644
index 0000000..3d03630
--- /dev/null
+++ b/k/atapi.c
@@ -0,0 +1,75 @@
+#include <k/atapi.h>
+#include <string.h>
+
+#include "atapi.h"
+#include "io.h"
+
+static struct atapi_drive drives[4] = { 0 };
+
+static void select_drive(uint16_t bus, uint8_t slave)
+{
+    outb(ATA_REG_DRIVE(bus), slave);
+}
+
+static void busy_wait(uint16_t drive)
+{
+    int res = 0;
+    while (res & BSY)
+        res = inb(ATA_REG_STATUS(drive));
+}
+
+static void wait_device_selection(uint16_t drive)
+{
+    for (int i = 0; i < 4; ++i)
+        inb(drive);
+}
+
+static uint8_t is_atapi_driver(uint16_t bus, uint8_t slave)
+{
+    static uint8_t atapi_sig[] = { ATAPI_SIG_SC, ATAPI_SIG_LBA_LO,
+                                   ATAPI_SIG_LBA_MI, ATAPI_SIG_LBA_HI };
+    uint8_t sig[4];
+
+    sig[0] = inb(ATA_REG_SECTOR_COUNT(bus));
+    sig[1] = inb(ATA_REG_LBA_LO(bus));
+    sig[2] = inb(ATA_REG_LBA_MI(bus));
+    sig[3] = inb(ATA_REG_LBA_HI(bus));
+
+    if (!memcmp(sig, atapi_sig, 4))
+    {
+        struct atapi_drive d = { bus, slave };
+        if (bus == PRIMARY_REG)
+        {
+            if (slave)
+                drives[1] = d;
+            else
+                drives[0] = d;
+        }
+        else
+        {
+            if (slave)
+                drives[3] = d;
+            else
+                drives[2] = d;
+        }
+
+        return 1;
+    }
+
+    return 0;
+}
+
+void discover_atapi_drive(void)
+{
+    // primary_reg
+    outb(PRIMARY_DCR, SRST);
+    outb(PRIMARY_DCR, INTERRUPT_DISABLE);
+
+    select_drive(PRIMARY_REG, ATA_PORT_MASTER);
+    wait_device_selection(PRIMARY_REG);
+    is_atapi_driver(PRIMARY_REG, ATA_PORT_MASTER);
+
+    // secondary_reg
+    outb(SECONDARY_DCR, SRST);
+    outb(SECONDARY_DCR, INTERRUPT_DISABLE);
+}
diff --git a/k/atapi.h b/k/atapi.h
new file mode 100644
index 0000000..dc4ec58
--- /dev/null
+++ b/k/atapi.h
@@ -0,0 +1,14 @@
+#ifndef ATAPI_H
+#define ATAPI_H
+
+#include <stdint.h>
+
+struct atapi_drive
+{
+    uint8_t reg;
+    uint8_t drive;
+};
+
+void discover_atapi_drive(void);
+
+#endif /* !ATAPI_H */