From 388c245ce40e65a4f7a635f76a05518779b14c15 Mon Sep 17 00:00:00 2001
From: TuxSH <1922548+TuxSH@users.noreply.github.com>
Date: Sun, 12 Jan 2020 01:59:26 +0000
Subject: [PATCH] thermosphere: add TransportInterface abstraction layer

---
 thermosphere/src/debug_log.c           |  13 +-
 thermosphere/src/debug_log.h           |   1 +
 thermosphere/src/irq.c                 | 116 +++++++---
 thermosphere/src/irq.h                 |  26 +--
 thermosphere/src/main.c                |  11 +-
 thermosphere/src/platform/qemu/uart.c  |  19 +-
 thermosphere/src/platform/qemu/uart.h  |   2 +
 thermosphere/src/platform/tegra/uart.c |  18 ++
 thermosphere/src/platform/tegra/uart.h |   2 +
 thermosphere/src/transport_interface.c | 301 +++++++++++++++++++++++++
 thermosphere/src/transport_interface.h |  56 +++++
 11 files changed, 499 insertions(+), 66 deletions(-)
 create mode 100644 thermosphere/src/transport_interface.c
 create mode 100644 thermosphere/src/transport_interface.h

diff --git a/thermosphere/src/debug_log.c b/thermosphere/src/debug_log.c
index 34fbff61f..e8eb6e497 100644
--- a/thermosphere/src/debug_log.c
+++ b/thermosphere/src/debug_log.c
@@ -19,11 +19,22 @@
 #include "platform/uart.h"
 #include "semihosting.h"
 #include "utils.h"
+#include "transport_interface.h"
+#include "platform/uart.h"
 
 #ifndef DLOG_USE_SEMIHOSTING_WRITE0
 #define DLOG_USE_SEMIHOSTING_WRITE0 1
 #endif
 
+static TransportInterface *g_debugLogTransportInterface;
+
+void debugLogInit(void)
+{
+    if (!DLOG_USE_SEMIHOSTING_WRITE0) {
+        transportInterfaceCreate(TRANSPORT_INTERFACE_TYPE_UART, DEFAULT_UART, DEFAULT_UART_FLAGS, NULL, NULL, NULL);
+    }
+}
+
 // NOTE: UNSAFE!
 int debugLog(const char *fmt, ...)
 {
@@ -37,7 +48,7 @@ int debugLog(const char *fmt, ...)
     if (DLOG_USE_SEMIHOSTING_WRITE0 && semihosting_connection_supported()) {
         semihosting_write_string(buf);
     } else {
-        uartWriteData(DEFAULT_UART, buf, (size_t)res);
+        transportInterfaceWriteData(g_debugLogTransportInterface, buf, res);
     }
 
     return res;
diff --git a/thermosphere/src/debug_log.h b/thermosphere/src/debug_log.h
index d8c46df85..8076d4f16 100644
--- a/thermosphere/src/debug_log.h
+++ b/thermosphere/src/debug_log.h
@@ -23,4 +23,5 @@
 #define DEBUG(...)
 #endif
 
+void debugLogInit(void);
 int debugLog(const char *fmt, ...);
diff --git a/thermosphere/src/irq.c b/thermosphere/src/irq.c
index e8385ce7e..87ed2b9b0 100644
--- a/thermosphere/src/irq.c
+++ b/thermosphere/src/irq.c
@@ -19,6 +19,7 @@
 #include "debug_log.h"
 #include "vgic.h"
 #include "timer.h"
+#include "transport_interface.h"
 
 IrqManager g_irqManager = {0};
 
@@ -98,40 +99,6 @@ static void initGic(void)
     currentCoreCtx->gicInterfaceMask = gicd->itargetsr[0];
 }
 
-void configureInterrupt(u16 id, u8 prio, bool isLevelSensitive)
-{
-    volatile ArmGicV2Distributor *gicd = g_irqManager.gic.gicd;
-    gicd->icenabler[id / 32] = BIT(id % 32);
-
-    if (id >= 32) {
-        u32 cfgr = gicd->icfgr[id / 16];
-        cfgr &= ~(3 << IRQ_CFGR_SHIFT(id));
-        cfgr |= (!isLevelSensitive ? 3 : 1) << IRQ_CFGR_SHIFT(id);
-        gicd->icfgr[id / 16] = cfgr;
-        gicd->itargetsr[id]  |= currentCoreCtx->gicInterfaceMask;
-    }
-    gicd->icpendr[id / 32]      = BIT(id % 32);
-    gicd->ipriorityr[id]        = (prio << g_irqManager.priorityShift) & 0xFF;
-    gicd->isenabler[id / 32]    = BIT(id % 32);
-}
-
-void initIrq(void)
-{
-    u64 flags = recursiveSpinlockLockMaskIrq(&g_irqManager.lock);
-
-    initGic();
-    vgicInit();
-
-    // Configure the interrupts we use here
-    for (u32 i = 0; i < ThermosphereSgi_Max; i++) {
-        configureInterrupt(i, IRQ_PRIORITY_HOST, false);
-    }
-
-    configureInterrupt(GIC_IRQID_MAINTENANCE, IRQ_PRIORITY_HOST, true);
-
-    recursiveSpinlockUnlockRestoreIrq(&g_irqManager.lock, flags);
-}
-
 static inline bool checkRescheduleEmulatedPtimer(ExceptionStackFrame *frame)
 {
     // Evaluate if the timer really has expired in the PoV of the guest kernel. If not, reschedule (add missed time delta) it & exit early
@@ -148,6 +115,75 @@ static inline bool checkRescheduleEmulatedPtimer(ExceptionStackFrame *frame)
     return true;
 }
 
+static void doConfigureInterrupt(u16 id, u8 prio, bool isLevelSensitive)
+{
+    volatile ArmGicV2Distributor *gicd = g_irqManager.gic.gicd;
+    gicd->icenabler[id / 32] = BIT(id % 32);
+
+    if (id >= 32) {
+        u32 cfgr = gicd->icfgr[id / 16];
+        cfgr &= ~(3 << IRQ_CFGR_SHIFT(id));
+        cfgr |= (!isLevelSensitive ? 3 : 1) << IRQ_CFGR_SHIFT(id);
+        gicd->icfgr[id / 16] = cfgr;
+        gicd->itargetsr[id]  = 0xFF; // all cpu interfaces
+    }
+    gicd->icpendr[id / 32]      = BIT(id % 32);
+    gicd->ipriorityr[id]        = (prio << g_irqManager.priorityShift) & 0xFF;
+    gicd->isenabler[id / 32]    = BIT(id % 32);
+}
+
+void initIrq(void)
+{
+    u64 flags = recursiveSpinlockLockMaskIrq(&g_irqManager.lock);
+
+    initGic();
+    vgicInit();
+
+    // Configure the interrupts we use here
+    for (u32 i = 0; i < ThermosphereSgi_Max; i++) {
+        doConfigureInterrupt(i, IRQ_PRIORITY_HOST, false);
+    }
+
+    doConfigureInterrupt(GIC_IRQID_MAINTENANCE, IRQ_PRIORITY_HOST, true);
+
+    recursiveSpinlockUnlockRestoreIrq(&g_irqManager.lock, flags);
+}
+
+void configureInterrupt(u16 id, u8 prio, bool isLevelSensitive)
+{
+    u64 flags = recursiveSpinlockLockMaskIrq(&g_irqManager.lock);
+    doConfigureInterrupt(id, prio, isLevelSensitive);
+    recursiveSpinlockUnlockRestoreIrq(&g_irqManager.lock, flags);
+}
+
+void irqSetAffinity(u16 id, u8 affinity)
+{
+    u64 flags = recursiveSpinlockLockMaskIrq(&g_irqManager.lock);
+    g_irqManager.gic.gicd->itargetsr[id] = affinity;
+    recursiveSpinlockUnlockRestoreIrq(&g_irqManager.lock, flags);
+}
+
+bool irqIsGuest(u16 id)
+{
+    if (id >= 32 + g_irqManager.numSharedInterrupts) {
+        DEBUG("vgic: %u not supported by physical distributor\n", (u32)id);
+        return false;
+    }
+
+    bool ret = true;
+    ret = ret && id != GIC_IRQID_MAINTENANCE;
+    ret = ret && id != GIC_IRQID_NS_PHYS_HYP_TIMER;
+
+    // If the following interrupts don't exist, that's fine, they're defined as GIC_IRQID_SPURIOUS in that case
+    // (for which the function isn't called, anyway)
+    ret = ret && id != GIC_IRQID_NS_VIRT_HYP_TIMER;
+    ret = ret && id != GIC_IRQID_SEC_PHYS_HYP_TIMER;
+    ret = ret && id != GIC_IRQID_SEC_VIRT_HYP_TIMER;
+
+    ret = ret && transportInterfaceFindByIrqId(id) == NULL;
+    return ret;
+}
+
 void handleIrqException(ExceptionStackFrame *frame, bool isLowerEl, bool isA32)
 {
     (void)isLowerEl;
@@ -159,7 +195,7 @@ void handleIrqException(ExceptionStackFrame *frame, bool isLowerEl, bool isA32)
     u32 irqId = iar & 0x3FF;
     u32 srcCore = (iar >> 10) & 7;
 
-    DEBUG("EL2 [core %d]: Received irq %x\n", (int)currentCoreCtx->coreId, irqId);
+    //DEBUG("EL2 [core %d]: Received irq %x\n", (int)currentCoreCtx->coreId, irqId);
 
     if (irqId == GIC_IRQID_SPURIOUS) {
         // Spurious interrupt received
@@ -192,10 +228,12 @@ void handleIrqException(ExceptionStackFrame *frame, bool isLowerEl, bool isA32)
             break;
     }
 
+    TransportInterface *transportIface = irqId >= 32 ? transportInterfaceIrqHandlerTopHalf(irqId) : NULL;
+
     // Priority drop
     gicc->eoir = iar;
 
-    isGuestInterrupt = isGuestInterrupt && irqIsGuest(irqId);
+    isGuestInterrupt = isGuestInterrupt && transportIface == NULL && irqIsGuest(irqId);
 
     recursiveSpinlockLock(&g_irqManager.lock);
 
@@ -213,4 +251,10 @@ void handleIrqException(ExceptionStackFrame *frame, bool isLowerEl, bool isA32)
     vgicUpdateState();
 
     recursiveSpinlockUnlock(&g_irqManager.lock);
+
+    // Bottom half part
+    if (transportIface != NULL) {
+        unmaskIrq();
+        transportInterfaceIrqHandlerBottomHalf(transportIface);
+    }
 }
diff --git a/thermosphere/src/irq.h b/thermosphere/src/irq.h
index 4f91fdf2a..6ca212a9e 100644
--- a/thermosphere/src/irq.h
+++ b/thermosphere/src/irq.h
@@ -21,7 +21,6 @@
 #include "exceptions.h"
 #include "utils.h"
 #include "platform/interrupt_config.h"
-#include "platform/uart.h"
 
 #define IRQ_PRIORITY_HOST       0
 #define IRQ_PRIORITY_GUEST      1
@@ -49,8 +48,10 @@ typedef enum ThermosphereSgi {
 extern IrqManager g_irqManager;
 
 void initIrq(void);
-void handleIrqException(ExceptionStackFrame *frame, bool isLowerEl, bool isA32);
 void configureInterrupt(u16 id, u8 prio, bool isLevelSensitive);
+bool irqIsGuest(u16 id);
+void irqSetAffinity(u16 id, u8 affinityMask);
+void handleIrqException(ExceptionStackFrame *frame, bool isLowerEl, bool isA32);
 
 static inline void generateSgiForAllOthers(ThermosphereSgi id)
 {
@@ -71,24 +72,3 @@ static inline void generateSgiForAll(ThermosphereSgi id)
 {
     generateSgiForList(id, MASK(g_irqManager.numCpuInterfaces));
 }
-
-static inline bool irqIsGuest(u16 id)
-{
-    if (id >= 32 + g_irqManager.numSharedInterrupts) {
-        DEBUG("vgic: %u not supported by physical distributor\n", (u32)id);
-        return false;
-    }
-
-    bool ret = id != GIC_IRQID_MAINTENANCE && id != GIC_IRQID_NS_PHYS_HYP_TIMER;
-    ret = ret && id != uartGetIrqId(DEFAULT_UART); // FIXME
-#if GIC_IRQID_NS_VIRT_HYP_TIMER != GIC_IRQID_SPURIOUS
-    ret = ret && id != GIC_IRQID_NS_VIRT_HYP_TIMER;
-#endif
-#if GIC_IRQID_SEC_PHYS_HYP_TIMER != GIC_IRQID_SPURIOUS
-    ret = ret && id != GIC_IRQID_SEC_PHYS_HYP_TIMER;
-#endif
-#if GIC_IRQID_SEC_VIRT_HYP_TIMER != GIC_IRQID_SPURIOUS
-    ret = ret && id != GIC_IRQID_SEC_VIRT_HYP_TIMER;
-#endif
-    return ret;
-}
diff --git a/thermosphere/src/main.c b/thermosphere/src/main.c
index 00375154e..dd957a04a 100644
--- a/thermosphere/src/main.c
+++ b/thermosphere/src/main.c
@@ -13,6 +13,7 @@
 #include "watchpoints.h"
 #include "timer.h"
 #include "irq.h"
+#include "transport_interface.h"
 
 extern const u8 __start__[];
 
@@ -39,18 +40,18 @@ static void loadKernelViaSemihosting(void)
 
 void thermosphereMain(ExceptionStackFrame *frame)
 {
-    enableTraps();
-    enableBreakpointsAndWatchpoints();
-    timerInit();
     initIrq();
 
     if (currentCoreCtx->isBootCore) {
-        uartInit(DEFAULT_UART, BAUD_115200, 0);
-        uartSetInterruptStatus(DEFAULT_UART, DIRECTION_READ, true);
+        transportInterfaceInitLayer();
+        debugLogInit();
 
         DEBUG("EL2: core %u reached main first!\n", currentCoreCtx->coreId);
     }
 
+    enableTraps();
+    enableBreakpointsAndWatchpoints();
+    timerInit();
     initBreakpoints();
     initWatchpoints();
 
diff --git a/thermosphere/src/platform/qemu/uart.c b/thermosphere/src/platform/qemu/uart.c
index 66fa09021..7734ca7b7 100644
--- a/thermosphere/src/platform/qemu/uart.c
+++ b/thermosphere/src/platform/qemu/uart.c
@@ -87,7 +87,6 @@ void uartInit(UartDevice dev, u32 baudRate, u32 flags)
 
     // Enable tx, rx, and uart overall
     uart->cr = PL011_UARTCR_RXE | PL011_UARTCR_TXE | PL011_UARTCR_UARTEN;
-    //uart->imsc = PL011_RTI | PL011_RXI | PL011_RXI;
 }
 
 void uartWriteData(UartDevice dev, const void *buffer, size_t size)
@@ -129,6 +128,24 @@ size_t uartReadDataMax(UartDevice dev, void *buffer, size_t maxSize)
     return count;
 }
 
+size_t uartReadDataUntil(UartDevice dev, char *buffer, size_t maxSize, char delimiter)
+{
+    volatile PL011UartRegisters *uart = uartGetRegisters(dev);
+
+    size_t count = 0;
+
+    for (size_t i = 0; i < maxSize; i++) {
+        while (uart->fr & PL011_UARTFR_RXFE);
+        buffer[i] = uart->dr;
+        ++count;
+        if (buffer[i] == delimiter) {
+            break;
+        }
+    }
+
+    return count;
+}
+
 ReadWriteDirection uartGetInterruptDirection(UartDevice dev)
 {
     volatile PL011UartRegisters *uart = uartGetRegisters(dev);
diff --git a/thermosphere/src/platform/qemu/uart.h b/thermosphere/src/platform/qemu/uart.h
index 523dea480..d266ff6ce 100644
--- a/thermosphere/src/platform/qemu/uart.h
+++ b/thermosphere/src/platform/qemu/uart.h
@@ -132,6 +132,8 @@ void uartInit(UartDevice dev, u32 baudRate, u32 flags);
 void uartWriteData(UartDevice dev, const void *buffer, size_t size);
 void uartReadData(UartDevice dev, void *buffer, size_t size);
 size_t uartReadDataMax(UartDevice dev, void *buffer, size_t maxSize);
+size_t uartReadDataUntil(UartDevice dev, char *buffer, size_t maxSize, char delimiter);
+
 ReadWriteDirection uartGetInterruptDirection(UartDevice dev);
 void uartSetInterruptStatus(UartDevice dev, ReadWriteDirection direction, bool enable);
 
diff --git a/thermosphere/src/platform/tegra/uart.c b/thermosphere/src/platform/tegra/uart.c
index 7664b2069..c6274f046 100644
--- a/thermosphere/src/platform/tegra/uart.c
+++ b/thermosphere/src/platform/tegra/uart.c
@@ -192,6 +192,24 @@ size_t uartReadDataMax(UartDevice dev, void *buffer, size_t maxSize)
     return count;
 }
 
+size_t uartReadDataUntil(UartDevice dev, char *buffer, size_t maxSize, char delimiter)
+{
+    volatile tegra_uart_t *uart = uartGetRegisters(dev);
+    size_t count = 0;
+
+    for (size_t i = 0; i < maxSize && (uart->lsr & UART_LSR_RDR); i++) {
+        while (!(uart->lsr & UART_LSR_RDR)) // Wait until it's possible to receive data.
+
+        buffer[i] = uart->rbr;
+        ++count;
+        if (buffer[i] == delimiter) {
+            break;
+        }
+    }
+
+    return count;
+}
+
 ReadWriteDirection uartGetInterruptDirection(UartDevice dev)
 {
     volatile tegra_uart_t *uart = uartGetRegisters(dev);
diff --git a/thermosphere/src/platform/tegra/uart.h b/thermosphere/src/platform/tegra/uart.h
index 70782224e..b2aeffc48 100644
--- a/thermosphere/src/platform/tegra/uart.h
+++ b/thermosphere/src/platform/tegra/uart.h
@@ -195,6 +195,8 @@ void uartInit(UartDevice dev, u32 baud, u32 flags);
 void uartWriteData(UartDevice dev, const void *buffer, size_t size);
 void uartReadData(UartDevice dev, void *buffer, size_t size);
 size_t uartReadDataMax(UartDevice dev, void *buffer, size_t maxSize);
+size_t uartReadDataUntil(UartDevice dev, char *buffer, size_t maxSize, char delimiter);
+
 ReadWriteDirection uartGetInterruptDirection(UartDevice dev);
 void uartSetInterruptStatus(UartDevice dev, ReadWriteDirection direction, bool enable);
 
diff --git a/thermosphere/src/transport_interface.c b/thermosphere/src/transport_interface.c
new file mode 100644
index 000000000..755949679
--- /dev/null
+++ b/thermosphere/src/transport_interface.c
@@ -0,0 +1,301 @@
+/*
+ * Copyright (c) 2019 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "transport_interface.h"
+#include "platform/uart.h"
+#include "core_ctx.h"
+#include "irq.h"
+
+#define FOREACH_LINK(link, list)\
+    for (TransportInterfaceLink *link = transportInterfaceListGetFirstLink(list); link != transportInterfaceListGetEndLink(list); link = link->next)
+
+typedef struct TransportInterfaceLink {
+    struct TransportInterfaceLink *prev, *next;
+} TransportInterfaceLink;
+
+struct TransportInterface {
+    TransportInterfaceLink link;
+    TransportInterfaceReceiveDataCallback receiveDataCallback;
+    TransportInterfaceProcessDataCallback processDataCallback;
+    void *ctx;
+    RecursiveSpinlock lock;
+    u32 id;
+    u32 flags;
+    TransportInterfaceType type;
+    // ignored ReadWriteDirection interruptDirection;
+};
+
+typedef struct TransportInterfaceList {
+    TransportInterfaceLink link;
+} TransportInterfaceList;
+
+static RecursiveSpinlock g_transportInterfaceLayerLock;
+static TransportInterface g_transportInterfaceStorage[MAX_TRANSPORT_INTERFACES];
+
+static TransportInterfaceList g_transportInterfaceList, g_transportInterfaceFreeList;
+
+static inline TransportInterfaceLink *transportInterfaceListGetLastLink(TransportInterfaceList *list)
+{
+    return list->link.prev;
+}
+
+static inline TransportInterfaceLink *transportInterfaceListGetFirstLink(TransportInterfaceList *list)
+{
+    return list->link.next;
+}
+
+static inline TransportInterfaceLink *transportInterfaceListGetEndLink(TransportInterfaceList *list)
+{
+    return &list->link;
+}
+
+static inline bool transportInterfaceListIsEmpty(TransportInterfaceList *list)
+{
+    return transportInterfaceListGetFirstLink(list) == transportInterfaceListGetEndLink(list);
+}
+
+static inline TransportInterface *transportInterfaceGetLinkParent(TransportInterfaceLink *link)
+{
+    // Static aliasing rules say the first member of a struct has the same address as the struct itself
+    return (TransportInterface *)link;
+}
+
+static inline void transportInterfaceListInit(TransportInterfaceList *list)
+{
+    list->link.prev = transportInterfaceListGetEndLink(list);
+    list->link.next = transportInterfaceListGetEndLink(list);
+}
+
+static inline void transportInterfaceListInsertAfter(TransportInterfaceLink *pos, TransportInterfaceLink *nd)
+{
+    // if pos is last & list is empty, ->next writes to first, etc.
+    pos->next->prev = nd;
+    nd->prev = pos;
+    nd->next = pos->next;
+    pos->next = nd;
+}
+
+static inline void transportInterfaceListInsertBefore(TransportInterfaceLink *pos, TransportInterfaceLink *nd)
+{
+    pos->prev->next = nd;
+    nd->prev = pos->prev;
+    nd->next = pos;
+    pos->prev = nd;
+}
+
+static inline void transportInterfaceListRemove(const TransportInterfaceLink *nd)
+{
+    nd->prev->next = nd->next;
+    nd->next->prev = nd->prev;
+}
+
+void transportInterfaceInitLayer(void)
+{
+    transportInterfaceListInit(&g_transportInterfaceList);
+    transportInterfaceListInit(&g_transportInterfaceFreeList);
+
+    for (u32 i = 0; i < MAX_TRANSPORT_INTERFACES; i++) {
+        transportInterfaceListInsertAfter(transportInterfaceListGetLastLink(&g_transportInterfaceFreeList), &g_transportInterfaceStorage[i].link);
+    }
+}
+
+TransportInterface *transportInterfaceCreate(
+    TransportInterfaceType type,
+    u32 id,
+    u32 flags,
+    TransportInterfaceReceiveDataCallback receiveDataCallback,
+    TransportInterfaceProcessDataCallback processDataCallback,
+    void *ctx
+)
+{
+    u64 irqFlags = recursiveSpinlockLockMaskIrq(&g_transportInterfaceLayerLock);
+    if (transportInterfaceListIsEmpty(&g_transportInterfaceFreeList)) {
+        PANIC("transportInterfaceCreateAndInit: resource exhaustion\n");
+    }
+
+    TransportInterface *iface;
+
+    FOREACH_LINK (link, &g_transportInterfaceList) {
+        iface = transportInterfaceGetLinkParent(link);
+        if (iface->type == type && iface->id == id) {
+            PANIC("transportInterfaceCreateAndInit: device already registered\n");
+        }
+    }
+
+    iface = transportInterfaceGetLinkParent(transportInterfaceListGetFirstLink(&g_transportInterfaceFreeList));
+
+    iface->type = type;
+    iface->id = id;
+    iface->receiveDataCallback = receiveDataCallback;
+    iface->processDataCallback = processDataCallback;
+    iface->ctx = ctx;
+
+    switch (type) {
+        case TRANSPORT_INTERFACE_TYPE_UART: {
+            UartDevice dev = (UartDevice)id;
+            uartInit(dev, BAUD_115200, flags);
+            uartSetInterruptStatus(id, DIRECTION_READ, iface->receiveDataCallback != NULL);
+            break;
+        }
+        default:
+            break;
+    }
+
+    transportInterfaceListRemove(&iface->link);
+    transportInterfaceListInsertAfter(transportInterfaceListGetLastLink(&g_transportInterfaceList), &iface->link);
+    recursiveSpinlockUnlockRestoreIrq(&g_transportInterfaceLayerLock, irqFlags);
+
+    return iface;
+}
+
+void transportInterfaceAcquire(TransportInterface *iface)
+{
+    // Get the lock, prevent the interrupt from being pending if there's incoming data
+    recursiveSpinlockLock(&iface->lock);
+
+    switch (iface->type) {
+        case TRANSPORT_INTERFACE_TYPE_UART: {
+            UartDevice dev = (UartDevice)iface->id;
+            uartSetInterruptStatus(dev, DIRECTION_READ, false);
+            break;
+        }
+        default:
+            break;
+    }
+}
+
+void transportInterfaceRelease(TransportInterface *iface)
+{
+    // See transportInterfaceAcquire
+    switch (iface->type) {
+        case TRANSPORT_INTERFACE_TYPE_UART: {
+            UartDevice dev = (UartDevice)iface->id;
+            uartSetInterruptStatus(dev, DIRECTION_READ, true);
+            break;
+        }
+        default:
+            break;
+    }
+
+    recursiveSpinlockUnlock(&iface->lock);
+}
+
+TransportInterface *transportInterfaceFindByIrqId(u16 irqId)
+{
+    u64 irqFlags = recursiveSpinlockLockMaskIrq(&g_transportInterfaceLayerLock);
+
+    TransportInterface *ret = NULL;
+    FOREACH_LINK (link, &g_transportInterfaceList) {
+        TransportInterface *iface = transportInterfaceGetLinkParent(link);
+        if (iface->type == TRANSPORT_INTERFACE_TYPE_UART && uartGetIrqId((UartDevice)iface->id) == irqId) {
+            ret = iface;
+            break;
+        }
+    }
+
+    recursiveSpinlockUnlockRestoreIrq(&g_transportInterfaceLayerLock, irqFlags);
+    return ret;
+}
+
+void transportInterfaceSetInterruptAffinity(TransportInterface *iface, u8 affinity)
+{
+    u64 irqFlags = recursiveSpinlockLockMaskIrq(&iface->lock);
+    switch (iface->type) {
+        case TRANSPORT_INTERFACE_TYPE_UART: {
+            UartDevice dev = (UartDevice)iface->id;
+            irqSetAffinity(uartGetIrqId(dev), affinity);
+            break;
+        }
+        default:
+            break;
+    }
+    recursiveSpinlockUnlockRestoreIrq(&iface->lock, irqFlags);
+}
+
+TransportInterface *transportInterfaceIrqHandlerTopHalf(u16 irqId)
+{
+    TransportInterface *iface = transportInterfaceFindByIrqId(irqId);
+    if (iface == NULL) {
+        PANIC("transportInterfaceLayerIrqHandlerTop: irq id %x not found!\n", irqId);
+    }
+
+    transportInterfaceAcquire(iface);
+
+    // Interrupt should have gone from active-and-pending to only active (on the GIC)
+    return iface;
+}
+
+void transportInterfaceIrqHandlerBottomHalf(TransportInterface *iface)
+{
+    size_t sz = iface->receiveDataCallback(iface, iface->ctx);
+    if (sz > 0 && iface->processDataCallback != NULL) {
+        iface->processDataCallback(iface, iface->ctx, sz);
+    }
+
+    transportInterfaceRelease(iface);
+}
+
+void transportInterfaceWriteData(TransportInterface *iface, const void *buffer, size_t size)
+{
+    switch (iface->type) {
+        case TRANSPORT_INTERFACE_TYPE_UART: {
+            UartDevice dev = (UartDevice)iface->id;
+            uartWriteData(dev, buffer, size);
+            break;
+        }
+        default:
+            break;
+    }
+}
+
+void transportInterfaceReadData(TransportInterface *iface, void *buffer, size_t size)
+{
+    switch (iface->type) {
+        case TRANSPORT_INTERFACE_TYPE_UART: {
+            UartDevice dev = (UartDevice)iface->id;
+            uartReadData(dev, buffer, size);
+            break;
+        }
+        default:
+            break;
+    }
+}
+
+size_t transportInterfaceReadDataMax(TransportInterface *iface, void *buffer, size_t maxSize)
+{
+    switch (iface->type) {
+        case TRANSPORT_INTERFACE_TYPE_UART: {
+            UartDevice dev = (UartDevice)iface->id;
+            return uartReadDataMax(dev, buffer, maxSize);
+        }
+        default:
+            return 0;
+            break;
+    }
+}
+
+size_t transportInterfaceReadDataUntil(TransportInterface *iface, char *buffer, size_t maxSize, char delimiter)
+{
+    switch (iface->type) {
+        case TRANSPORT_INTERFACE_TYPE_UART: {
+            UartDevice dev = (UartDevice)iface->id;
+            return uartReadDataUntil(dev, buffer, maxSize, delimiter);
+        }
+        default:
+            return 0;
+            break;
+    }
+}
diff --git a/thermosphere/src/transport_interface.h b/thermosphere/src/transport_interface.h
new file mode 100644
index 000000000..b9f6d1e25
--- /dev/null
+++ b/thermosphere/src/transport_interface.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2019 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "utils.h"
+#include "spinlock.h"
+
+#define MAX_TRANSPORT_INTERFACES    4
+
+typedef enum TransportInterfaceType {
+    TRANSPORT_INTERFACE_TYPE_UART = 0,
+
+    TRANSPORT_INTERFACE_TYPE_MAX,
+} TransportInterfaceType;
+
+struct TransportInterface;
+typedef struct TransportInterface TransportInterface;
+typedef size_t (*TransportInterfaceReceiveDataCallback)(TransportInterface *iface, void *ctx);
+typedef void (*TransportInterfaceProcessDataCallback)(TransportInterface *iface, void *ctx, size_t dataSize);
+
+void transportInterfaceInitLayer(void);
+TransportInterface *transportInterfaceCreate(
+    TransportInterfaceType type,
+    u32 id,
+    u32 flags,
+    TransportInterfaceReceiveDataCallback receiveDataCallback,
+    TransportInterfaceProcessDataCallback processDataCallback,
+    void *ctx
+);
+void transportInterfaceAcquire(TransportInterface *iface);
+void transportInterfaceRelease(TransportInterface *iface);
+
+TransportInterface *transportInterfaceFindByIrqId(u16 irqId);
+void transportInterfaceSetInterruptAffinity(TransportInterface *iface, u8 affinity);
+
+TransportInterface *transportInterfaceIrqHandlerTopHalf(u16 irqId);
+void transportInterfaceIrqHandlerBottomHalf(TransportInterface *iface);
+
+void transportInterfaceWriteData(TransportInterface *iface, const void *buffer, size_t size);
+void transportInterfaceReadData(TransportInterface *iface, void *buffer, size_t size);
+size_t transportInterfaceReadDataMax(TransportInterface *iface, void *buffer, size_t maxSize);
+size_t transportInterfaceReadDataUntil(TransportInterface *iface, char *buffer, size_t maxSize, char delimiter);