Kernel: Move TTY-related code to a new subdirectory under Devices

The TTY subsystem is represented with unix devices, so it should be
under the Devices directory like the Audio, Storage, GPU and HID
subsystems.

Kernel/Devices/TTY/SlavePTY.cpp

@@ -0,0 +1,114 @@
+/*
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Singleton.h>
+#include <Kernel/Debug.h>
+#include <Kernel/Devices/TTY/MasterPTY.h>
+#include <Kernel/Devices/TTY/SlavePTY.h>
+#include <Kernel/Tasks/Process.h>
+
+namespace Kernel {
+
+static Singleton<SpinlockProtected<SlavePTY::List, LockRank::None>> s_all_instances;
+
+SpinlockProtected<SlavePTY::List, LockRank::None>& SlavePTY::all_instances()
+{
+    return s_all_instances;
+}
+
+bool SlavePTY::unref() const
+{
+    bool did_hit_zero = SlavePTY::all_instances().with([&](auto&) {
+        if (deref_base())
+            return false;
+        m_list_node.remove();
+        const_cast<SlavePTY&>(*this).revoke_weak_ptrs();
+        return true;
+    });
+    if (did_hit_zero) {
+        const_cast<SlavePTY&>(*this).will_be_destroyed();
+        delete this;
+    }
+    return did_hit_zero;
+}
+
+SlavePTY::SlavePTY(NonnullRefPtr<MasterPTY> master, UserID uid, GroupID gid, unsigned index)
+    : TTY(201, index)
+    , m_master(move(master))
+    , m_index(index)
+    , m_uid(uid)
+    , m_gid(gid)
+{
+    set_size(80, 25);
+    SlavePTY::all_instances().with([&](auto& list) { list.append(*this); });
+}
+
+SlavePTY::~SlavePTY()
+{
+    dbgln_if(SLAVEPTY_DEBUG, "~SlavePTY({})", m_index);
+}
+
+ErrorOr<NonnullOwnPtr<KString>> SlavePTY::pseudo_name() const
+{
+    return KString::formatted("pts:{}", m_index);
+}
+
+void SlavePTY::echo(u8 ch)
+{
+    if (should_echo_input()) {
+        auto buffer = UserOrKernelBuffer::for_kernel_buffer(&ch);
+        [[maybe_unused]] auto result = m_master->on_slave_write(buffer, 1);
+    }
+}
+
+void SlavePTY::on_master_write(UserOrKernelBuffer const& buffer, size_t size)
+{
+    auto result = buffer.read_buffered<128>(size, [&](ReadonlyBytes data) {
+        for (const auto& byte : data)
+            emit(byte, false);
+        return data.size();
+    });
+    if (!result.is_error())
+        evaluate_block_conditions();
+}
+
+ErrorOr<size_t> SlavePTY::on_tty_write(UserOrKernelBuffer const& data, size_t size)
+{
+    m_time_of_last_write = kgettimeofday();
+    return m_master->on_slave_write(data, size);
+}
+
+bool SlavePTY::can_write(OpenFileDescription const&, u64) const
+{
+    return m_master->can_write_from_slave();
+}
+
+bool SlavePTY::can_read(OpenFileDescription const& description, u64 offset) const
+{
+    if (m_master->is_closed())
+        return true;
+    return TTY::can_read(description, offset);
+}
+
+ErrorOr<size_t> SlavePTY::read(OpenFileDescription& description, u64 offset, UserOrKernelBuffer& buffer, size_t size)
+{
+    if (m_master->is_closed())
+        return 0;
+    return TTY::read(description, offset, buffer, size);
+}
+
+ErrorOr<void> SlavePTY::close()
+{
+    m_master->notify_slave_closed({});
+    return {};
+}
+
+FileBlockerSet& SlavePTY::blocker_set()
+{
+    return m_master->blocker_set();
+}
+
+}