[[PageOutline]]
== Migrate old os_''youros''.cpp to new class interface ==

Christian Franke wrote this quick outline how a migration works, which he already tested with os_linux.cpp.

=== Step 1: Move adapter classes into os_''youros''.cpp ===

 * Append adapter classes to old module:
{{{
#!sh
$ cat dev_legacy.cpp >> os_youros.cpp
}}}
 * Re-configure, this should now detect new interface:
{{{
#!sh
$ ./configure
...
checking whether os_youros.cpp uses new interface... yes
}}}
 * This should compile and work!
 * Move #includes to top, remove duplicates.
 * Remove all dummy functions for controllers not supported on your os (marvell_command_interface, ...).
 * Remove corresponding classes (e.g legacy_marvell_device, ...).
 * Remove corresponding section from legacy_smart_interface::get_custom_smart_device(). If nothing left, remove this function.
 * Rename remaining classes 'legacy_*' to 'youros_*'. Rename namespace 'os' to 'os_youros'.
 * This should compile and work!

=== Step 2: Merge old functions into class member functions ===

'''Old:'''
{{{
#!c
int deviceopen(const char *pathname, char *type)
{
  ...
  int fd = open(pathname, ...);
  ...
  return fd;
}

bool youros_smart_device::open()
{
  m_fd = ::deviceopen(get_dev_name(), (char*)m_mode);
  if (m_fd < 0) {
    set_err(errno);
    return false;
  }
  return true;
}
}}}

'''New:'''
{{{
#!cpp
bool youros_smart_device::open()
{
  ...
  m_fd = ::open(get_dev_name(), ...);
  if (m_fd < 0) {
    set_err(errno);
    return false;
  }
  return true;
}
}}}

'''Old:'''
{{{
#!c
int ata_command_interface(int fd, smart_command_set command, int select, char *data)
{
  ...
  if (ioctl(fd, ...))
    return -1;
  ...
  return 0;
}

int youros_ata_device::ata_command_interface(smart_command_set command, int select, char * data)
{
  return ::ata_command_interface(get_fd(), command, select, data);
}
}}}

'''New:'''
{{{
#!cpp
int youros_ata_device::ata_command_interface(smart_command_set command, int select, char * data)
{
  ...
  if (ioctl(get_fd(), ...))
    return -1;
  ...
  return 0;
}
}}}


=== Step 3: Convert SMART-only to full fledged ATA pass through ===

 * Change base class of 'youros_ata_device' from 'ata_device_with_command_set' to 'ata_device'.
 * Change 'youros_ata_device::ata_command_interface()' to 'youros_ata_device::ata_pass_through()'.
 * Add parameter check using ata_cmd_is_ok(in, 'supported features')
 * Remove 'switch (command) {....}', set ioctl input struct directly from input registers e.g. 'in.in_regs.*'.
 * Remove special handling for SMART STATUS, return result registers in 'out.out_regs' if requested by 'in.out_needed.is_set()'.
 * Adjust returns:
   * Replace 'return 0;' by 'return true;'.
   * Replace 'errno = ERR; return -1;' by 'return set_err(ERR, "optional message", ...)'.
 * Optional add 48bit ATA pass through support:
   * If 'in.in_regs.is_48bit_cmd()' is set, pass low (in.in_regs.lba_mid) and high (in.in_regs.prev.lba_mid) byte of each register to ioctl.

=== Later ===
 * Rework device scanning.
 * Add/Rework auto-detection (function autodetect_open()).
 * remove os_youros.h, each module does only export smart_interface::init().

=== Example for Steps 1+2: ===
See changeset r2623

=== Example for Step 3 (3ware only): ===
See changeset r2624