1. 10 Jan, 2006 5 commits
    • 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
      more.
      
      Description:
      
      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
      transfer.
      
      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>
      33f0f88f
    • Paul Mundt's avatar
      Input: remove obsolete maple input drivers · 94f8d28c
      Paul Mundt authored
      These haven't worked in some time, and we've dropped support for the bus
      from the SH tree until someone shows some interest in maintaining it.
      Signed-off-by: default avatarPaul Mundt <lethal@linux-sh.org>
      Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
      94f8d28c
    • Arjan van de Ven's avatar
      Input: prepare for f_ops constness · e2bd470e
      Arjan van de Ven authored
      Avoid doing assignments to a live ->fops so it can be marked as 'const'.
      Signed-off-by: default avatarArjan van de Ven <arjan@infradead.org>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
      e2bd470e
    • Miloslav Trmac's avatar
      Input: wistron - do not crash if BIOS does not support interface · c28c3583
      Miloslav Trmac authored
      offset can never be < 0 because it has type size_t.  The driver
      currently oopses on insmod if BIOS does not support the interface,
      instead of refusing to load.
      Signed-off-by: default avatarMiloslav Trmac <mitr@volny.cz>
      Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
      c28c3583
    • Dmitry Torokhov's avatar
      Input: grip_mp - kill commented out code · ebbac7dd
      Dmitry Torokhov authored
      Kill leftovers of dynalloc conversion.
      Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
      ebbac7dd
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