update_engine/mtd_file_descriptor.h

// Copyright 2014 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UPDATE_ENGINE_MTD_FILE_DESCRIPTOR_H_
#define UPDATE_ENGINE_MTD_FILE_DESCRIPTOR_H_

// This module defines file descriptors that deal with NAND media. We are
// concerned with raw NAND access (as MTD device), and through UBI layer.

#include <mtdutils.h>

#include "update_engine/file_descriptor.h"

namespace chromeos_update_engine {

// A class defining the file descriptor API for raw MTD device. This file
// descriptor supports either random read, or sequential write but not both at
// once.
class MtdFileDescriptor : public EintrSafeFileDescriptor {
 public:
  MtdFileDescriptor();

  static bool IsMtd(const char* path);

  bool Open(const char* path, int flags, mode_t mode) override;
  bool Open(const char* path, int flags) override;
  ssize_t Read(void* buf, size_t count) override;
  ssize_t Write(const void* buf, size_t count) override;
  off64_t Seek(off64_t offset, int whence) override;
  void Reset() override;

 private:
  std::unique_ptr<MtdReadContext, decltype(&mtd_read_close)> read_ctx_;
  std::unique_ptr<MtdWriteContext, decltype(&mtd_write_close)> write_ctx_;
};

// TODO(namnguyen) This is a placeholder struct. This struct, and the
// UbiFileDescriptor class below will need finalized later.
struct UbiVolumeInfo {
  uint64_t size;
};

// A file descriptor to update a UBI volume, similar to MtdFileDescriptor.
// Once the file descriptor is opened for write, the volume is marked as being
// updated. The volume will not be usable until an update is completed. See
// UBI_IOCVOLUP ioctl operation.
// TODO(namnguyen) Again, this needs fleshed out when we have better library to
// interact with UBI volumes. I would expect this class to be very similar to
// MtdFileDescriptor, with two different contexts to bridge C-C++ divide.
class UbiFileDescriptor : public EintrSafeFileDescriptor {
 public:
  static bool IsUbi(const char* path);

  bool Open(const char* path, int flags, mode_t mode) override;
  bool Open(const char* path, int flags) override;
  ssize_t Read(void* buf, size_t count) override;
  ssize_t Write(const void* buf, size_t count) override;
  off64_t Seek(off64_t offset, int whence) override;
  void Reset() override;

 private:
  std::unique_ptr<UbiVolumeInfo> CreateWriteContext(const char* path);

  std::unique_ptr<UbiVolumeInfo> read_ctx_;
  std::unique_ptr<UbiVolumeInfo> write_ctx_;
};

}  // namespace chromeos_update_engine

#endif  // UPDATE_ENGINE_MTD_FILE_DESCRIPTOR_H_