1. 12 Jan, 2006 1 commit
  2. 10 Jan, 2006 1 commit
    • Alan Cox's avatar
      [PATCH] TTY layer buffering revamp · 33f0f88f
      Alan Cox authored
      The API and code have been through various bits of initial review by
      serial driver people but they definitely need to live somewhere for a
      while so the unconverted drivers can get knocked into shape, existing
      drivers that have been updated can be better tuned and bugs whacked out.
      This replaces the tty flip buffers with kmalloc objects in rings. In the
      normal situation for an IRQ driven serial port at typical speeds the
      behaviour is pretty much the same, two buffers end up allocated and the
      kernel cycles between them as before.
      When there are delays or at high speed we now behave far better as the
      buffer pool can grow a bit rather than lose characters. This also means
      that we can operate at higher speeds reliably.
      For drivers that receive characters in blocks (DMA based, USB and
      especially virtualisation) the layer allows a lot of driver specific
      code that works around the tty layer with private secondary queues to be
      removed. The IBM folks need this sort of layer, the smart serial port
      people do, the virtualisers do (because a virtualised tty typically
      operates at infinite speed rather than emulating 9600 baud).
      Finally many drivers had invalid and unsafe attempts to avoid buffer
      overflows by directly invoking tty methods extracted out of the innards
      of work queue structs. These are no longer needed and all go away. That
      fixes various random hangs with serial ports on overflow.
      The other change in here is to optimise the receive_room path that is
      used by some callers. It turns out that only one ldisc uses receive room
      except asa constant and it updates it far far less than the value is
      read. We thus make it a variable not a function call.
      I expect the code to contain bugs due to the size alone but I'll be
      watching and squashing them and feeding out new patches as it goes.
      Because the buffers now dynamically expand you should only run out of
      buffering when the kernel runs out of memory for real.  That means a lot of
      the horrible hacks high performance drivers used to do just aren't needed any
      tty_insert_flip_char is an old API and continues to work as before, as does
      tty_flip_buffer_push() [this is why many drivers dont need modification].  It
      does now also return the number of chars inserted
      There are also
      tty_buffer_request_room(tty, len)
      which asks for a buffer block of the length requested and returns the space
      found.  This improves efficiency with hardware that knows how much to
      and tty_insert_flip_string_flags(tty, str, flags, len)
      to insert a string of characters and flags
      For a smart interface the usual code is
          len = tty_request_buffer_room(tty, amount_hardware_says);
          tty_insert_flip_string(tty, buffer_from_card, len);
      More description!
      At the moment tty buffers are attached directly to the tty.  This is causing a
      lot of the problems related to tty layer locking, also problems at high speed
      and also with bursty data (such as occurs in virtualised environments)
      I'm working on ripping out the flip buffers and replacing them with a pool of
      dynamically allocated buffers.  This allows both for old style "byte I/O"
      devices and also helps virtualisation and smart devices where large blocks of
      data suddenely materialise and need storing.
      So far so good.  Lots of drivers reference tty->flip.*.  Several of them also
      call directly and unsafely into function pointers it provides.  This will all
      break.  Most drivers can use tty_insert_flip_char which can be kept as an API
      but others need more.
      At the moment I've added the following interfaces, if people think more will
      be needed now is a good time to say
       int tty_buffer_request_room(tty, size)
      Try and ensure at least size bytes are available, returns actual room (may be
      zero).  At the moment it just uses the flipbuf space but that will change.
      Repeated calls without characters being added are not cumulative.  (ie if you
      call it with 1, 1, 1, and then 4 you'll have four characters of space.  The
      other functions will also try and grow buffers in future but this will be a
      more efficient way when you know block sizes.
       int tty_insert_flip_char(tty, ch, flag)
      As before insert a character if there is room.  Now returns 1 for success, 0
      for failure.
       int tty_insert_flip_string(tty, str, len)
      Insert a block of non error characters.  Returns the number inserted.
       int tty_prepare_flip_string(tty, strptr, len)
      Adjust the buffer to allow len characters to be added.  Returns a buffer
      pointer in strptr and the length available.  This allows for hardware that
      needs to use functions like insl or mencpy_fromio.
      Signed-off-by: default avatarAlan Cox <alan@redhat.com>
      Cc: Paul Fulghum <paulkf@microgate.com>
      Signed-off-by: default avatarHirokazu Takata <takata@linux-m32r.org>
      Signed-off-by: default avatarSerge Hallyn <serue@us.ibm.com>
      Signed-off-by: default avatarJeff Dike <jdike@addtoit.com>
      Signed-off-by: default avatarJohn Hawkes <hawkes@sgi.com>
      Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
      Signed-off-by: default avatarAdrian Bunk <bunk@stusta.de>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
  3. 07 Jan, 2006 1 commit
    • Dave Jones's avatar
      [SERIAL] Make the number of UARTs registered configurable. · a61c2d78
      Dave Jones authored
      Also add a nr_uarts module option to the 8250 code to override
      this, up to a maximum of CONFIG_SERIAL_8250_NR_UARTS
      This should appease people who complain about a proliferation
      of /dev/ttyS & /sysfs nodes whilst at the same time allowing
      a single kernel image to support the rarer occasions of
      lots of devices.
      Signed-off-by: default avatarDave Jones <davej@redhat.com>
  4. 04 Jan, 2006 4 commits
  5. 28 Nov, 2005 1 commit
  6. 12 Nov, 2005 1 commit
    • Lennert Buytenhek's avatar
      [SERIAL] don't disable xscale serial ports after autoconfig · 5c8c755c
      Lennert Buytenhek authored
      xscale-type UARTs have an extra bit (UUE) in the IER register that has
      to be written as 1 to enable the UART.  At the end of autoconfig() in
      drivers/serial/8250.c, the IER register is unconditionally written as
      zero, which turns off the UART, and makes any subsequent printch() hang
      the box.
      Since other 8250-type UARTs don't have this enable bit and are thus
      always 'enabled' in this sense, it can't hurt to enable xscale-type
      serial ports all the time as well.  The attached patch changes the
      autoconfig() exit path to see if the port has an UUE enable bit, and if
      yes, to write UUE=1 instead of just putting a zero into IER, using the
      same test as is used at the beginning of serial8250_console_write().
      Signed-off-by: default avatarLennert Buytenhek <buytenh@wantstofly.org>
      Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
  7. 09 Nov, 2005 1 commit
  8. 07 Nov, 2005 1 commit
  9. 06 Nov, 2005 1 commit
  10. 29 Oct, 2005 1 commit
  11. 28 Oct, 2005 1 commit
  12. 09 Sep, 2005 1 commit
  13. 08 Sep, 2005 1 commit
  14. 31 Aug, 2005 1 commit
  15. 30 Jun, 2005 1 commit
  16. 29 Jun, 2005 3 commits
  17. 27 Jun, 2005 1 commit
    • Russell King's avatar
      [PATCH] Serial: Split 8250 port table · ec9f47cd
      Russell King authored
      Add separate files for the different 8250 ISA-based serial boards.
      Looking across all the various architectures, it seems reasonable that
      we can key the availability of the configuration options for these
      beasts to the bus-related symbols (iow, CONFIG_ISA).  We also standardise
      the base baud/uart clock rate for these boards - I'm sure that isn't
      architecture specific, but is solely dependent on the crystal fitted
      on the board (which should be the same no matter what type of machine
      its fitted into.)
      Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
  18. 24 Jun, 2005 1 commit
  19. 23 Jun, 2005 3 commits
  20. 21 May, 2005 1 commit
  21. 09 May, 2005 1 commit
  22. 01 May, 2005 1 commit
  23. 16 Apr, 2005 2 commits
    • Russell King's avatar
      [PATCH] serial: fix comments in 8250.c · 23907eb8
      Russell King authored
      Fix the formatting of some comments in 8250.c, and add a note that the
      register_serial / unregister_serial shouldn't be used in new code.
      We do this here in preference to adding to linux/serial.h, since that is used
      by a number of non-8250 drivers which pretend to be 8250.  It is not known
      whether it would be appropriate to do so.
      Signed-off-by: default avatarRussell King <rmk@arm.linux.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    • Linus Torvalds's avatar
      Linux-2.6.12-rc2 · 1da177e4
      Linus Torvalds authored
      Initial git repository build. I'm not bothering with the full history,
      even though we have it. We can create a separate "historical" git
      archive of that later if we want to, and in the meantime it's about
      3.2GB when imported into git - space that would just make the early
      git days unnecessarily complicated, when we don't have a lot of good
      infrastructure for it.
      Let it rip!