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authorAlan Cox <alan@lxorguk.ukuu.org.uk>2006-01-09 23:54:13 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-01-10 11:01:59 -0500
commit33f0f88f1c51ae5c2d593d26960c760ea154c2e2 (patch)
treef53a38cf49406863f079d74d0e8f91b276f7c1a9 /drivers/s390/char
parent6ed80991a2dce4afc113be35089c564d62fa1f11 (diff)
[PATCH] TTY layer buffering revamp
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 <alan@redhat.com> Cc: Paul Fulghum <paulkf@microgate.com> Signed-off-by: Hirokazu Takata <takata@linux-m32r.org> Signed-off-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: Jeff Dike <jdike@addtoit.com> Signed-off-by: John Hawkes <hawkes@sgi.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/s390/char')
-rw-r--r--drivers/s390/char/con3215.c25
-rw-r--r--drivers/s390/char/sclp_tty.c21
-rw-r--r--drivers/s390/char/sclp_vt220.c12
3 files changed, 18 insertions, 40 deletions
diff --git a/drivers/s390/char/con3215.c b/drivers/s390/char/con3215.c
index 75419cf9d353..1f060914cfa4 100644
--- a/drivers/s390/char/con3215.c
+++ b/drivers/s390/char/con3215.c
@@ -16,6 +16,7 @@
16#include <linux/types.h> 16#include <linux/types.h>
17#include <linux/kdev_t.h> 17#include <linux/kdev_t.h>
18#include <linux/tty.h> 18#include <linux/tty.h>
19#include <linux/tty_flip.h>
19#include <linux/vt_kern.h> 20#include <linux/vt_kern.h>
20#include <linux/init.h> 21#include <linux/init.h>
21#include <linux/console.h> 22#include <linux/console.h>
@@ -432,8 +433,6 @@ raw3215_irq(struct ccw_device *cdev, unsigned long intparm, struct irb *irb)
432 if (count > slen) 433 if (count > slen)
433 count = slen; 434 count = slen;
434 } else 435 } else
435 if (count >= TTY_FLIPBUF_SIZE - tty->flip.count)
436 count = TTY_FLIPBUF_SIZE - tty->flip.count - 1;
437 EBCASC(raw->inbuf, count); 436 EBCASC(raw->inbuf, count);
438 cchar = ctrlchar_handle(raw->inbuf, count, tty); 437 cchar = ctrlchar_handle(raw->inbuf, count, tty);
439 switch (cchar & CTRLCHAR_MASK) { 438 switch (cchar & CTRLCHAR_MASK) {
@@ -441,28 +440,20 @@ raw3215_irq(struct ccw_device *cdev, unsigned long intparm, struct irb *irb)
441 break; 440 break;
442 441
443 case CTRLCHAR_CTRL: 442 case CTRLCHAR_CTRL:
444 tty->flip.count++; 443 tty_insert_flip_char(tty, cchar, TTY_NORMAL);
445 *tty->flip.flag_buf_ptr++ = TTY_NORMAL;
446 *tty->flip.char_buf_ptr++ = cchar;
447 tty_flip_buffer_push(raw->tty); 444 tty_flip_buffer_push(raw->tty);
448 break; 445 break;
449 446
450 case CTRLCHAR_NONE: 447 case CTRLCHAR_NONE:
451 memcpy(tty->flip.char_buf_ptr,
452 raw->inbuf, count);
453 if (count < 2 || 448 if (count < 2 ||
454 (strncmp(raw->inbuf+count-2, "^n", 2) && 449 (strncmp(raw->inbuf+count-2, "\252n", 2) &&
455 strncmp(raw->inbuf+count-2, "\252n", 2)) ) { 450 strncmp(raw->inbuf+count-2, "^n", 2)) ) {
456 /* don't add the auto \n */ 451 /* add the auto \n */
457 tty->flip.char_buf_ptr[count] = '\n'; 452 raw->inbuf[count] = '\n';
458 memset(tty->flip.flag_buf_ptr,
459 TTY_NORMAL, count + 1);
460 count++; 453 count++;
461 } else 454 } else
462 count-=2; 455 count -= 2;
463 tty->flip.char_buf_ptr += count; 456 tty_insert_flip_string(tty, raw->inbuf, count);
464 tty->flip.flag_buf_ptr += count;
465 tty->flip.count += count;
466 tty_flip_buffer_push(raw->tty); 457 tty_flip_buffer_push(raw->tty);
467 break; 458 break;
468 } 459 }
diff --git a/drivers/s390/char/sclp_tty.c b/drivers/s390/char/sclp_tty.c
index a20d7c89341d..6cbf067f1a8f 100644
--- a/drivers/s390/char/sclp_tty.c
+++ b/drivers/s390/char/sclp_tty.c
@@ -13,6 +13,7 @@
13#include <linux/kmod.h> 13#include <linux/kmod.h>
14#include <linux/tty.h> 14#include <linux/tty.h>
15#include <linux/tty_driver.h> 15#include <linux/tty_driver.h>
16#include <linux/tty_flip.h>
16#include <linux/sched.h> 17#include <linux/sched.h>
17#include <linux/wait.h> 18#include <linux/wait.h>
18#include <linux/slab.h> 19#include <linux/slab.h>
@@ -496,25 +497,19 @@ sclp_tty_input(unsigned char* buf, unsigned int count)
496 case CTRLCHAR_SYSRQ: 497 case CTRLCHAR_SYSRQ:
497 break; 498 break;
498 case CTRLCHAR_CTRL: 499 case CTRLCHAR_CTRL:
499 sclp_tty->flip.count++; 500 tty_insert_flip_char(sclp_tty, cchar, TTY_NORMAL);
500 *sclp_tty->flip.flag_buf_ptr++ = TTY_NORMAL;
501 *sclp_tty->flip.char_buf_ptr++ = cchar;
502 tty_flip_buffer_push(sclp_tty); 501 tty_flip_buffer_push(sclp_tty);
503 break; 502 break;
504 case CTRLCHAR_NONE: 503 case CTRLCHAR_NONE:
505 /* send (normal) input to line discipline */ 504 /* send (normal) input to line discipline */
506 memcpy(sclp_tty->flip.char_buf_ptr, buf, count);
507 if (count < 2 || 505 if (count < 2 ||
508 (strncmp ((const char *) buf + count - 2, "^n", 2) && 506 (strncmp((const char *) buf + count - 2, "^n", 2) &&
509 strncmp ((const char *) buf + count - 2, "\0252n", 2))) { 507 strncmp((const char *) buf + count - 2, "\252n", 2))) {
510 sclp_tty->flip.char_buf_ptr[count] = '\n'; 508 /* add the auto \n */
511 count++; 509 tty_insert_flip_string(sclp_tty, buf, count);
510 tty_insert_flip_char(sclp_tty, '\n', TTY_NORMAL);
512 } else 511 } else
513 count -= 2; 512 tty_insert_flip_string(sclp_tty, buf, count - 2);
514 memset(sclp_tty->flip.flag_buf_ptr, TTY_NORMAL, count);
515 sclp_tty->flip.char_buf_ptr += count;
516 sclp_tty->flip.flag_buf_ptr += count;
517 sclp_tty->flip.count += count;
518 tty_flip_buffer_push(sclp_tty); 513 tty_flip_buffer_push(sclp_tty);
519 break; 514 break;
520 } 515 }
diff --git a/drivers/s390/char/sclp_vt220.c b/drivers/s390/char/sclp_vt220.c
index 06bd85824d7b..9e02625c82cf 100644
--- a/drivers/s390/char/sclp_vt220.c
+++ b/drivers/s390/char/sclp_vt220.c
@@ -16,6 +16,7 @@
16#include <linux/kernel.h> 16#include <linux/kernel.h>
17#include <linux/tty.h> 17#include <linux/tty.h>
18#include <linux/tty_driver.h> 18#include <linux/tty_driver.h>
19#include <linux/tty_flip.h>
19#include <linux/sched.h> 20#include <linux/sched.h>
20#include <linux/errno.h> 21#include <linux/errno.h>
21#include <linux/mm.h> 22#include <linux/mm.h>
@@ -482,16 +483,7 @@ sclp_vt220_receiver_fn(struct evbuf_header *evbuf)
482 /* Send input to line discipline */ 483 /* Send input to line discipline */
483 buffer++; 484 buffer++;
484 count--; 485 count--;
485 /* Prevent buffer overrun by discarding input. Note that 486 tty_insert_flip_string(sclp_vt220_tty, buffer, count);
486 * because buffer_push works asynchronously, we cannot wait
487 * for the buffer to be emptied. */
488 if (count + sclp_vt220_tty->flip.count > TTY_FLIPBUF_SIZE)
489 count = TTY_FLIPBUF_SIZE - sclp_vt220_tty->flip.count;
490 memcpy(sclp_vt220_tty->flip.char_buf_ptr, buffer, count);
491 memset(sclp_vt220_tty->flip.flag_buf_ptr, TTY_NORMAL, count);
492 sclp_vt220_tty->flip.char_buf_ptr += count;
493 sclp_vt220_tty->flip.flag_buf_ptr += count;
494 sclp_vt220_tty->flip.count += count;
495 tty_flip_buffer_push(sclp_vt220_tty); 487 tty_flip_buffer_push(sclp_vt220_tty);
496 break; 488 break;
497 } 489 }