user/sven/linux.git/drivers/char/selection.c, branch v2.6.16.20

[PATCH] TTY layer buffering revamp

2006-01-10T16:01:59Z

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: Alan Cox Cc: Paul Fulghum Signed-off-by: Hirokazu Takata Signed-off-by: Serge Hallyn Signed-off-by: Jeff Dike Signed-off-by: John Hawkes Signed-off-by: Martin Schwidefsky Signed-off-by: Adrian Bunk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] kfree cleanup: drivers/char

2005-11-07T15:54:02Z

This is the drivers/char/ part of the big kfree cleanup patch. Remove pointless checks for NULL prior to calling kfree() in drivers/char/. Signed-off-by: Jesper Juhl Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] verify_area cleanup : drivers part 1

2005-03-13T08:28:06Z

This patch converts the first half of drivers from verify_area to access_ok. Signed-off-by: Jesper Juhl Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] merge vt_struct into vc_data

2005-03-08T01:45:57Z

The vt_struct and vc_data are always allocated together, so there is no need for a separate vt_struct structure. Signed-off-by: Roman Zippel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] cleanup vc array access

2005-03-08T01:45:28Z

This removes as far as possible unneccessary vc_cons lookups by using a pointer to the vc_data structure instead of the index. The hidden currcons argument in console_macros.h is temporarily replaced with a hidden vc pointer. Signed-off-by: Roman Zippel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] cleanup virtual console <-> selection.c interface

2005-01-11T01:20:37Z

Pass around pointers instead of indices into a global array between various files of the virtual console implementation and stop using obsfucting macros that expect certain variables to be in scope. This is a first step to get rid of the various global arrays in the VC code. Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] unexport set_selection and paste_selection

2004-10-28T01:30:36Z

Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] tty locking cleanup and fixes

2004-09-29T07:05:39Z

No problems reported other than Linus typo in an unbuildable driver from the last one. This one adds tty_ldisc_flush and also makes tty_wakeup do the queue wake as discussed with Paul. I've then propagated these functions through all the drivers. This means most drivers don't know about the ldisc locking and instead call generic functions that look after it. The result is the removal of a lot of duplicate code both for ldisc referencing and historical code for handling tty ldisc wakeup semantics. A nice side effect is that by adding versions of the two helpers we can switch most of the drivers over before changing the core tty code if preferred. Signed-off-by: Linus Torvalds

[PATCH] drivers/char/selection.c MIN/MAX removal

2004-09-03T03:32:58Z

Signed-off-by: Maximilian Attems Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] sparse: NULL vs 0 - drivers/char/*

2004-06-30T08:50:54Z