From 604c2a843d95921e0429ebbdd5849174e47a9547 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Thu, 16 Jul 2026 17:30:17 +0200
Subject: kernel: begin block device re-architecture work

---
 kapi/kapi/devices.hpp              |  1 +
 kapi/kapi/devices/block_device.hpp | 51 ++++++++++++++++++++++++++++++++++++++
 kapi/kapi/devices/device.hpp       |  6 -----
 kapi/kapi/filesystem.hpp           |  6 +++--
 4 files changed, 56 insertions(+), 8 deletions(-)
 create mode 100644 kapi/kapi/devices/block_device.hpp

(limited to 'kapi')

diff --git a/kapi/kapi/devices.hpp b/kapi/kapi/devices.hpp
index 64820f7c..989ca0fa 100644
--- a/kapi/kapi/devices.hpp
+++ b/kapi/kapi/devices.hpp
@@ -1,6 +1,7 @@
 #ifndef TEACHOS_KAPI_DEVICES_HPP
 #define TEACHOS_KAPI_DEVICES_HPP
 
+#include <kapi/devices/block_device.hpp>        // IWYU pragma: export
 #include <kapi/devices/bus.hpp>                 // IWYU pragma: export
 #include <kapi/devices/cpu.hpp>                 // IWYU pragma: export
 #include <kapi/devices/device.hpp>              // IWYU pragma: export
diff --git a/kapi/kapi/devices/block_device.hpp b/kapi/kapi/devices/block_device.hpp
new file mode 100644
index 00000000..4b3eab61
--- /dev/null
+++ b/kapi/kapi/devices/block_device.hpp
@@ -0,0 +1,51 @@
+#ifndef TEACHOS_KAPI_DEVICES_BLOCK_INTERFACE_HPP
+#define TEACHOS_KAPI_DEVICES_BLOCK_INTERFACE_HPP
+
+// IWYU pragma: private, include <kapi/devices.hpp>
+
+#include <kapi/devices/interface.hpp>
+
+#include <kstd/result.hpp>
+#include <kstd/units.hpp>
+
+#include <cstddef>
+
+namespace kapi::devices
+{
+
+  struct block_device
+  {
+    constexpr auto static id = interface{"block"};
+
+    //! Virtual destructor to enable clean deletes through base pointers.
+    virtual ~block_device() = default;
+
+    //! Read data from a block into a given buffer.
+    //!
+    //! If the selected block is smaller than the buffer, a partial read will occur.
+    //!
+    //! @param block_index The number of the block to read from.
+    //! @param buffer The buffer to read into.
+    //! @return The number of bytes read on success, an error otherwise.
+    [[nodiscard]] auto virtual read_block(size_t block_index, void * buffer) const
+        -> kstd::result<kstd::units::bytes> = 0;
+
+    //! Write data from a buffer into a block.
+    //!
+    //! If the buffer is larger than the selected block, a partial write will occur.
+    //!
+    //! @param block_index The number of the block to write to.
+    //! @param buffer The buffer to write from.
+    //! @return The number of bytes written on success, an error otherwise.
+    auto virtual write_block(std::size_t block_index, void const * buffer) -> kstd::result<kstd::units::bytes> = 0;
+
+    //! Get the block size in bytes.
+    [[nodiscard]] auto virtual block_size() const -> kstd::units::bytes = 0;
+
+    //! Get the capacity of the associated device.
+    [[nodiscard]] auto virtual capacity() const -> kstd::units::bytes = 0;
+  };
+
+}  // namespace kapi::devices
+
+#endif
\ No newline at end of file
diff --git a/kapi/kapi/devices/device.hpp b/kapi/kapi/devices/device.hpp
index e99dd5f8..bf91dfcf 100644
--- a/kapi/kapi/devices/device.hpp
+++ b/kapi/kapi/devices/device.hpp
@@ -76,12 +76,6 @@ namespace kapi::devices
      */
     [[nodiscard]] auto name() const -> kstd::string const &;
 
-    /**
-     * @brief Check if the device is a block device.
-     * @return true if this device is a block device, false otherwise.
-     */
-    [[nodiscard]] virtual auto is_block_device() const -> bool;
-
   protected:
     auto virtual query_interface(interface interface) -> void *;
 
diff --git a/kapi/kapi/filesystem.hpp b/kapi/kapi/filesystem.hpp
index 0f092d29..f293692d 100644
--- a/kapi/kapi/filesystem.hpp
+++ b/kapi/kapi/filesystem.hpp
@@ -3,6 +3,7 @@
 
 #include <kstd/result.hpp>
 #include <kstd/system_error.hpp>
+#include <kstd/units.hpp>
 
 #include <cstddef>
 #include <expected>
@@ -50,14 +51,15 @@ namespace kapi::filesystem
   //! @param file_descriptor The file descriptor to read from.
   //! @param buffer The buffer to store the read data.
   //! @return The number of bytes read on success, an error code otherwise.
-  auto read(size_t file_descriptor, std::span<std::byte> buffer) -> std::expected<std::size_t, kstd::error_code>;
+  auto read(size_t file_descriptor, std::span<std::byte> buffer) -> std::expected<kstd::units::bytes, kstd::error_code>;
 
   //! Write bytes from a given buffer to a file descriptor.
   //!
   //! @param file_descriptor The file descriptor to write to.
   //! @param buffer The buffer containing the data to write.
   //! @return The number of bytes written on success, an error code otherwise.
-  auto write(size_t file_descriptor, std::span<std::byte const> buffer) -> std::expected<std::size_t, kstd::error_code>;
+  auto write(size_t file_descriptor, std::span<std::byte const> buffer)
+      -> std::expected<kstd::units::bytes, kstd::error_code>;
 
   //! Create a new directory at the specified path.
   //!
-- 
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