Kernel: Make UserOrKernelBuffer R/W helpers return KResultOr<size_t>

This makes error propagation less cumbersome (and also exposed some
places where we were not doing it.)

4 files changed, 13 insertions, 23 deletions

diff --git a/Kernel/Devices/AsyncDeviceRequest.h b/Kernel/Devices/AsyncDeviceRequest.h
index ab8ed3c626..b5c0035627 100644
--- a/Kernel/Devices/AsyncDeviceRequest.h
+++ b/Kernel/Devices/AsyncDeviceRequest.h
@@ -90,7 +90,7 @@ public:
     }
 
     template<size_t BUFFER_BYTES, typename... Args>
-    [[nodiscard]] bool write_to_buffer_buffered(UserOrKernelBuffer& buffer, Args... args)
+    [[nodiscard]] KResultOr<size_t> write_to_buffer_buffered(UserOrKernelBuffer& buffer, Args... args)
     {
         if (in_target_context(buffer))
             return buffer.write_buffered<BUFFER_BYTES>(forward<Args>(args)...);
@@ -108,7 +108,7 @@ public:
     }
 
     template<size_t BUFFER_BYTES, typename... Args>
-    [[nodiscard]] bool read_from_buffer_buffered(const UserOrKernelBuffer& buffer, Args... args)
+    [[nodiscard]] KResultOr<size_t> read_from_buffer_buffered(const UserOrKernelBuffer& buffer, Args... args)
     {
         if (in_target_context(buffer))
             return buffer.read_buffered<BUFFER_BYTES>(forward<Args>(args)...);
diff --git a/Kernel/Devices/HID/KeyboardDevice.cpp b/Kernel/Devices/HID/KeyboardDevice.cpp
index f9e87e4ea7..b49603cbf9 100644
--- a/Kernel/Devices/HID/KeyboardDevice.cpp
+++ b/Kernel/Devices/HID/KeyboardDevice.cpp
@@ -298,13 +298,13 @@ KResultOr<size_t> KeyboardDevice::read(FileDescription&, u64, UserOrKernelBuffer
 
         lock.unlock();
 
-        ssize_t n = buffer.write_buffered<sizeof(Event)>(sizeof(Event), [&](u8* data, size_t data_bytes) {
+        auto result = buffer.write_buffered<sizeof(Event)>(sizeof(Event), [&](u8* data, size_t data_bytes) {
             memcpy(data, &event, sizeof(Event));
-            return (ssize_t)data_bytes;
+            return data_bytes;
         });
-        if (n < 0)
-            return KResult((ErrnoCode)-n);
-        VERIFY((size_t)n == sizeof(Event));
+        if (result.is_error())
+            return result.error();
+        VERIFY(result.value() == sizeof(Event));
         nread += sizeof(Event);
 
         lock.lock();
diff --git a/Kernel/Devices/RandomDevice.cpp b/Kernel/Devices/RandomDevice.cpp
index 589ed1eeb3..6ada0a36d4 100644
--- a/Kernel/Devices/RandomDevice.cpp
+++ b/Kernel/Devices/RandomDevice.cpp
@@ -25,13 +25,10 @@ bool RandomDevice::can_read(const FileDescription&, size_t) const
 
 KResultOr<size_t> RandomDevice::read(FileDescription&, u64, UserOrKernelBuffer& buffer, size_t size)
 {
-    bool success = buffer.write_buffered<256>(size, [&](u8* data, size_t data_size) {
+    return buffer.write_buffered<256>(size, [&](u8* data, size_t data_size) {
         get_good_random_bytes(data, data_size);
-        return (ssize_t)data_size;
+        return data_size;
     });
-    if (!success)
-        return EFAULT;
-    return size;
 }
 
 KResultOr<size_t> RandomDevice::write(FileDescription&, u64, const UserOrKernelBuffer&, size_t size)
diff --git a/Kernel/Devices/SerialDevice.cpp b/Kernel/Devices/SerialDevice.cpp
index 263c684ffd..3be348172a 100644
--- a/Kernel/Devices/SerialDevice.cpp
+++ b/Kernel/Devices/SerialDevice.cpp
@@ -33,15 +33,11 @@ KResultOr<size_t> SerialDevice::read(FileDescription&, u64, UserOrKernelBuffer&
     if (!(get_line_status() & DataReady))
         return 0;
 
-    ssize_t nwritten = buffer.write_buffered<128>(size, [&](u8* data, size_t data_size) {
+    return buffer.write_buffered<128>(size, [&](u8* data, size_t data_size) {
         for (size_t i = 0; i < data_size; i++)
             data[i] = IO::in8(m_base_addr);
-        return (ssize_t)data_size;
+        return data_size;
     });
-    if (nwritten < 0)
-        return KResult((ErrnoCode)-nwritten);
-
-    return size;
 }
 
 bool SerialDevice::can_write(const FileDescription&, size_t) const
@@ -57,14 +53,11 @@ KResultOr<size_t> SerialDevice::write(FileDescription&, u64, const UserOrKernelB
     if (!(get_line_status() & EmptyTransmitterHoldingRegister))
         return 0;
 
-    ssize_t nread = buffer.read_buffered<128>(size, [&](const u8* data, size_t data_size) {
+    return buffer.read_buffered<128>(size, [&](u8 const* data, size_t data_size) {
         for (size_t i = 0; i < data_size; i++)
             IO::out8(m_base_addr, data[i]);
-        return (ssize_t)data_size;
+        return data_size;
     });
-    if (nread < 0)
-        return KResult((ErrnoCode)-nread);
-    return (size_t)nread;
 }
 
 String SerialDevice::device_name() const