kernel+init: Create a device node in /dev to access the CDROM from userspace!

Still using PIO, though.

kernel/src/arch/x86_64/disk/ATA.cpp

@@ -4,6 +4,7 @@
 #include "arch/Timer.h"
 #include "arch/x86_64/IO.h"
 #include "memory/MemoryManager.h"
+#include <luna/Alignment.h>
 #include <luna/CType.h>
 #include <luna/SafeArithmetic.h>
 #include <luna/Vector.h>
@@ -329,6 +330,12 @@ namespace ATA
                     m_drives[drive] = {};
                     return false;
                 }
+
+                if (ATADevice::create(m_drives[drive]).has_error())
+                {
+                    kwarnln("ata: Failed to register ATA drive %d:%d in DeviceRegistry", m_channel_index, drive);
+                    continue;
+                }
             }
         }
 
@@ -675,6 +682,25 @@ namespace ATA
         return send_packet_atapi_pio(&read_packet, out, (u16)size);
     }
 
+    Result<void> Drive::read_lba(u64 lba, void* out, usize nblocks)
+    {
+        const usize blocks_per_page = ARCH_PAGE_SIZE / m_block_size;
+        if (m_is_atapi)
+        {
+            kdbgln("ata: Reading %zu blocks from ATAPI drive using PIO, at LBA %ld", nblocks, lba);
+            while (nblocks > blocks_per_page)
+            {
+                TRY(atapi_read_pio(lba, out, ARCH_PAGE_SIZE));
+                lba += blocks_per_page;
+                nblocks -= blocks_per_page;
+                out = offset_ptr(out, ARCH_PAGE_SIZE);
+            }
+            return atapi_read_pio(lba, out, nblocks * m_block_size);
+        }
+        else
+            todo();
+    }
+
     void Drive::irq_handler()
     {
         // Clear the IRQ flag.
@@ -694,3 +720,61 @@ namespace ATA
         }
     }
 }
+
+static u32 next_minor = 0;
+
+Result<void> ATADevice::create(SharedPtr<ATA::Drive> drive)
+{
+    auto device = TRY(adopt_shared_if_nonnull(new (std::nothrow) ATADevice()));
+    device->m_drive = drive;
+    return DeviceRegistry::register_special_device(DeviceRegistry::Disk, next_minor++, device);
+}
+
+Result<u64> ATADevice::read(u8* buf, usize offset, usize size) const
+{
+    if (size == 0) return 0;
+
+    if (offset > m_drive->capacity()) return 0;
+    if (offset + size > m_drive->capacity()) size = m_drive->capacity() - offset;
+
+    usize length = size;
+
+    auto block_size = m_drive->block_size();
+
+    auto* temp = TRY(make_array<u8>(block_size));
+    auto guard = make_scope_guard([temp] { delete[] temp; });
+
+    if (offset % block_size)
+    {
+        usize extra_size = block_size - (offset % block_size);
+        TRY(m_drive->read_lba(offset / block_size, temp, 1));
+        memcpy(buf, temp + (offset % block_size), extra_size);
+        offset += extra_size;
+        size -= extra_size;
+        buf += extra_size;
+    }
+
+    while (size >= ARCH_PAGE_SIZE)
+    {
+        TRY(m_drive->read_lba(offset / block_size, buf, ARCH_PAGE_SIZE / block_size));
+        offset += ARCH_PAGE_SIZE;
+        size -= ARCH_PAGE_SIZE;
+        buf += ARCH_PAGE_SIZE;
+    }
+
+    while (size >= block_size)
+    {
+        TRY(m_drive->read_lba(offset / block_size, buf, 1));
+        offset += block_size;
+        size -= block_size;
+        buf += block_size;
+    }
+
+    if (size)
+    {
+        TRY(m_drive->read_lba(offset / block_size, temp, 1));
+        memcpy(buf, temp, size);
+    }
+
+    return length;
+}

kernel/src/arch/x86_64/disk/ATA.h

@@ -142,6 +142,23 @@ namespace ATA
 
         void irq_handler();
 
+        usize block_size() const
+        {
+            return m_block_size;
+        }
+
+        usize block_count() const
+        {
+            return m_block_count;
+        }
+
+        usize capacity() const
+        {
+            return m_block_count * m_block_size;
+        }
+
+        Result<void> read_lba(u64 lba, void* out, usize nblocks);
+
       private:
         bool identify_ata();
 
@@ -265,23 +282,28 @@ class ATADevice : public Device
 {
   public:
     // Initializer for DeviceRegistry.
-    static Result<void> create(SharedPtr<ATA::Controller> controller, int channel, int drive);
+    static Result<void> create(SharedPtr<ATA::Drive> drive);
 
     Result<usize> read(u8*, usize, usize) const override;
 
-    Result<usize> write(const u8*, usize, usize) override;
+    Result<usize> write(const u8*, usize, usize) override
+    {
+        return err(ENOTSUP);
+    }
 
-    bool blocking() const override;
+    bool blocking() const override
+    {
+        return false;
+    }
 
-    Result<u64> ioctl(int request, void* arg) override;
+    usize size() const override
-
+    {
-    usize size() const override;
+        return m_drive->capacity();
+    }
 
     virtual ~ATADevice() = default;
 
   private:
-    ATADevice(SharedPtr<ATA::Controller> controller);
+    ATADevice() = default;
-    SharedPtr<ATA::Controller> m_controller;
+    SharedPtr<ATA::Drive> m_drive;
-    int m_channel;
-    int m_drive;
 };

kernel/src/fs/devices/DeviceRegistry.h

@@ -12,6 +12,7 @@ namespace DeviceRegistry
         Console = 1,
         Memory = 2,
         Framebuffer = 3,
+        Disk = 4,
     };
 
     Result<SharedPtr<Device>> fetch_special_device(u32 major, u32 minor);