MFC r344855 (by jhb):

Drop "All rights reserved" from my copyright statements.

Reviewed by: rgrimes
Differential Revision: https://reviews.freebsd.org/D19485

Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

sys/dev: minor spelling fixes.

Most affect comments, very few have user-visible effects.

sys/dev: use our nitems() macro when it is avaliable through param.h.

No functional change, only trivial cases are done in this sweep,
Drivers that can get further enhancements will be done independently.

Discussed in: freebsd-current

Migrate many bus_alloc_resource() calls to bus_alloc_resource_anywhere().

Most calls to bus_alloc_resource() use "anywhere" as the range, with a given
count. Migrate these to use the new bus_alloc_resource_anywhere() API.

Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D5370

o break newbus api: add a new argument of type driver_filter_t to
bus_setup_intr()

o add an int return code to all fast handlers

o retire INTR_FAST/IH_FAST

For more info: http://docs.freebsd.org/cgi/getmsg.cgi?fetch=465712+0+current/freebsd-current

Reviewed by: many
Approved by: re@

- Use swi_remove() to teardown swi handlers rather than
intr_event_remove_handler().
- Remove tty: prefix from a couple of swi handler names.

Catch up with new interrupt handling code.

Eliminate two unused arguments to ttycreate().

Start each of the license/copyright comments with /*-, minor shuffle of lines

Use generic ttycode instead of local copy.

Preparation commit for the tty cleanups that will follow in the near
future:

rename ttyopen() -> tty_open() and ttyclose() -> tty_close().

We need the ttyopen() and ttyclose() for the new generic cdevsw
functions for tty devices in order to have consistent naming.

Introduce ttygone() which indicates that the hardware is detached.

Move dtrwait logic to the generic TTY level.

Define the tty methods as typedefs.

Change the return type for t_break to void.

Add t_ioctl (more about this later).

Pick the hotchar out of the tty structure instead of caching private
copies.

No current line disciplines have a dynamically changing hotchar, and
expecting to receive anything sensible during a change in ldisc is
insane so no locking of the hotchar field is necessary.

Use generic support for BREAK and modem control ioctls

Do the dreaded s/dev_t/struct cdev */
Bump __FreeBSD_version accordingly.

Centralize the line discipline optimization determination in a function
called ttyldoptim().

Use this function from all the relevant drivers.

I belive no drivers finger linesw[] directly anymore, paving the way for
locking and refcounting.

Manual edits to change linesw[]-frobbing to ttyld_*() calls.

Machine generated patch which changes linedisc calls from accessing
linesw[] directly to using the ttyld...() functions

The ttyld...() functions ar inline so there is no performance hit.

Make the remaining serial drivers call ttyioctl() rather than calling
the linedisc directly.

There is no need to explicitly call the stop function. In all likelyhood
->l_close() did it and ttyclose certainly will.

Add missing <sys/module.h> includes

Convert callers to the new bus_alloc_resource_any(9) API.

Submitted by: Mark Santcroos <marks@ripe.net>
Reviewed by: imp, dfr, bde

Device megapatch 4/6:

Introduce d_version field in struct cdevsw, this must always be
initialized to D_VERSION.

Flip sense of D_NOGIANT flag to D_NEEDGIANT, this involves removing
four D_NOGIANT flags and adding 145 D_NEEDGIANT flags.

Device megapatch 3/6:

Add missing D_TTY flags to various drivers.

Complete asserts that dev_t's passed to ttyread(), ttywrite(),
ttypoll() and ttykqwrite() have (d_flags & D_TTY) and a struct tty
pointer.

Make ttyread(), ttywrite(), ttypoll() and ttykqwrite() the default
cdevsw methods for D_TTY drivers and remove the explicit initializations
in various drivers cdevsw structures.

Device megapatch 1/6:

Free approx 86 major numbers with a mostly automatically generated patch.

A number of strategic drivers have been left behind by caution, and a few
because they still (ab)use their major number.

Consistently use the BSD u_int and u_short instead of the SYSV uint and
ushort. In most of these files, there was a mixture of both styles and
this change just makes them self-consistent.

Requested by: bde (kern_ktrace.c)

Make TTYHOG tunable.

Reviewed by: mike (mentor)

Make nokqfilter() return the correct return value.

Ditch the D_KQFILTER flag which was used to prevent calling NULL pointers.

Gigacommit to improve device-driver source compatibility between
branches:

Initialize struct cdevsw using C99 sparse initializtion and remove
all initializations to default values.

This patch is automatically generated and has been tested by compiling
LINT with all the fields in struct cdevsw in reverse order on alpha,
sparc64 and i386.

Approved by: re(scottl)

More low-hanging fruit: kill caddr_t in calls to wakeup(9) / [mt]sleep(9).

Move an optimization check so that it breaks out of the correct loop.
Basically, as soon as we have run out of events to handle in the swi,
we stop looping through all the channels in a for loop.

Remove #include <sys/dkstat.h>

Use critical_enter/exit instead of disable/enable_intr to make this
driver more portable.

Cast si_drv2 to intptr_t instead of int to quiet warnings.

Tested on: alpha
Reported by: marcel (on an ia64)

- New-bussify the rc(4) device driver.
- Add detach support to the driver so that you can kldunload the module.
Note that currently rc_detach() fails to detach a unit if any of its
child devices are open, thus a kldunload will fail if any of the tty
devices are currently open.
- sys/i386/isa/ic/cd180.h was moved to sys/dev/ic/cd180.h as part of
this change.

Requested by: rwatson
Tested by: rwatson

Be consistent about funtions being static.

Spotte by: FlexeLint.

Off-by-128 error in the cuam* device node numbers.

Bump the rc driver a little bit closer to the 21st century: use
make_dev() to create device nodes for each of the serial port channels
(ttym%d and cuam%d respectively, as borrowed from MAKEDEV). This allows
the rc driver to work in 5.0. I've tested it with only one card, but
will try sticking in a second card tomorrow and see what happens.

Change the suser() API to take advantage of td_ucred as well as do a
general cleanup of the API. The entire API now consists of two functions
similar to the pre-KSE API. The suser() function takes a thread pointer
as its only argument. The td_ucred member of this thread must be valid
so the only valid thread pointers are curthread and a few kernel threads
such as thread0. The suser_cred() function takes a pointer to a struct
ucred as its first argument and an integer flag as its second argument.
The flag is currently only used for the PRISON_ROOT flag.

Discussed on: smp@

Fixed some style bugs in the removal of __P(()). The main ones were
not removing tabs before "__P((", and not outdenting continuation lines
to preserve non-KNF lining up of code with parentheses. Switch to KNF
formatting and/or rewrap the whole prototype in some cases.

Remove __P.

Change the preemption code for software interrupt thread schedules and
mutex releases to not require flags for the cases when preemption is
not allowed:

The purpose of the MTX_NOSWITCH and SWI_NOSWITCH flags is to prevent
switching to a higher priority thread on mutex releease and swi schedule,
respectively when that switch is not safe. Now that the critical section
API maintains a per-thread nesting count, the kernel can easily check
whether or not it should switch without relying on flags from the
programmer. This fixes a few bugs in that all current callers of
swi_sched() used SWI_NOSWITCH, when in fact, only the ones called from
fast interrupt handlers and the swi_sched of softclock needed this flag.
Note that to ensure that swi_sched()'s in clock and fast interrupt
handlers do not switch, these handlers have to be explicitly wrapped
in critical_enter/exit pairs. Presently, just wrapping the handlers is
sufficient, but in the future with the fully preemptive kernel, the
interrupt must be EOI'd before critical_exit() is called. (critical_exit()
can switch due to a deferred preemption in a fully preemptive kernel.)

I've tested the changes to the interrupt code on i386 and alpha. I have
not tested ia64, but the interrupt code is almost identical to the alpha
code, so I expect it will work fine. PowerPC and ARM do not yet have
interrupt code in the tree so they shouldn't be broken. Sparc64 is
broken, but that's been ok'd by jake and tmm who will be fixing the
interrupt code for sparc64 shortly.

Reviewed by: peter
Tested on: i386, alpha

KSE Milestone 2
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.

Sorry john! (your next MFC will be a doosie!)

Reviewed by: peter@freebsd.org, dillon@freebsd.org

X-MFC after: ha ha ha ha

Remove unneeded includes of sys/ipl.h and machine/ipl.h.

Send the remains (such as I have located) of "block major numbers" to
the bit-bucket.

Extend kqueue down to the device layer.

Backwards compatible approach suggested by: peter

Catch up to the new swi API.

Move suser() and suser_xxx() prototypes and a related #define from
<sys/proc.h> to <sys/systm.h>.

Correctly document the #includes needed in the manpage.

Add one now needed #include of <sys/systm.h>.
Remove the consequent 48 unused #includes of <sys/proc.h>.

Catch up to the new software interrupt code.

Noticed by: phk

- Overhaul the software interrupt code to use interrupt threads for each
type of software interrupt. Roughly, what used to be a bit in spending
now maps to a swi thread. Each thread can have multiple handlers, just
like a hardware interrupt thread.
- Instead of using a bitmask of pending interrupts, we schedule the specific
software interrupt thread to run, so spending, NSWI, and the shandlers
array are no longer needed. We can now have an arbitrary number of
software interrupt threads. When you register a software interrupt
thread via sinthand_add(), you get back a struct intrhand that you pass
to sched_swi() when you wish to schedule your swi thread to run.
- Convert the name of 'struct intrec' to 'struct intrhand' as it is a bit
more intuitive. Also, prefix all the members of struct intrhand with
'ih_'.
- Make swi_net() a MI function since there is now no point in it being
MD.

Submitted by: cp

Remove unneeded #include <machine/clock.h>

Made this file compile again after move of stuff from <machine.ipl.h>
to <sys/ipl.h>.

Mass update of isa drivers using compatability shims to use
COMPAT_ISA_DRIVER() so that we can get rid of the evil isa_compat.h table.

Remove #if NFOO > 0 (it's not required in most cases) and also where it
isn't used as a result, remove #include "foo.h". Many of these drivers
still use NFOO for softc struct sizing etc however.

Introduce ttyread() and ttywrite() which do the canonical thing.

Use them in many tty drivers.

Reviewed by: julian, bde

Remove five now unused fields from struct cdevsw. They should never
have been there in the first place. A GENERIC kernel shrinks almost 1k.

Add a slightly different safetybelt under nostop for tty drivers.

Add some missing FreeBSD tags

This patch clears the way for removing a number of tty related
fields in struct cdevsw:

d_stop moved to struct tty.
d_reset already unused.
d_devtotty linkage now provided by dev_t->si_tty.

These fields will be removed from struct cdevsw together with
d_params and d_maxio Real Soon Now.

The changes in this patch consist of:

initialize dev->si_tty in *_open()
initialize tty->t_stop
remove devtotty functions
rename ttpoll to ttypoll
a few adjustments to these changes in the generic code
a bump of __FreeBSD_version
add a couple of FreeBSD tags

Convert DEVFS hooks in (most) drivers to make_dev().

Diskslice/label code not yet handled.

Vinum, i4b, alpha, pc98 not dealt with (left to respective Maintainers)

Add the correct hook for devfs to kern_conf.c

The net result of this excercise is that a lot less files depends on DEVFS,
and devtoname() gets more sensible output in many cases.

A few drivers had minor additional cleanups performed relating to cdevsw
registration.

A few drivers don't register a cdevsw{} anymore, but only use make_dev().

Fixed null setting of `rc_started'. This was fixed for the
corresponding variable `rc_wakeup_started' in rev.1.36 but broken
again in rev.1.37. This bug only caused excessive polling (it gave
NRC activations for each of the SWI handler and the timeout handler
instead of 1 of each).

Moved cdevsw attachment from the driver probe routine to the driver
attach routine.

Simplify cdevsw registration.

The cdevsw_add() function now finds the major number(s) in the
struct cdevsw passed to it. cdevsw_add_generic() is no longer
needed, cdevsw_add() does the same thing.

cdevsw_add() will print an message if the d_maj field looks bogus.

Remove nblkdev and nchrdev variables. Most places they were used
bogusly. Instead check a dev_t for validity by seeing if devsw()
or bdevsw() returns NULL.

Move bdevsw() and devsw() functions to kern/kern_conf.c

Bump __FreeBSD_version to 400006

This commit removes:
72 bogus makedev() calls
26 bogus SYSINIT functions

if_xe.c bogusly accessed cdevsw[], author/maintainer please fix.

I4b and vinum not changed. Patches emailed to authors. LINT
probably broken until they catch up.

This commit should be a extensive NO-OP:

Reformat and initialize correctly all "struct cdevsw".

Initialize the d_maj and d_bmaj fields.

The d_reset field was not removed, although it is never used.

I used a program to do most of this, so all the files now use the
same consistent format. Please keep it that way.

Vinum and i4b not modified, patches emailed to respective authors.

Add brackets around && within || to quieten egcs. I've checked the code
and I'm reasonably sure it's right, but I don't have one of the beasties.

Fix up a few easy 'assignment used as truth value' and 'suggest parens
around && within ||' type warnings. I'm pretty sure I have not masked
any problems here, I've committed real problem fixes seperately.

s/static foo_devsw_installed = 0;/static int foo_devsw_installed;/.
(Edited automatically)

Suser() simplification:

1:
s/suser/suser_xxx/

2:
Add new function: suser(struct proc *), prototyped in <sys/proc.h>.

3:
s/suser_xxx(\([a-zA-Z0-9_]*\)->p_ucred, \&\1->p_acflag)/suser(\1)/

The remaining suser_xxx() calls will be scrutinized and dealt with
later.

There may be some unneeded #include <sys/cred.h>, but they are left
as an exercise for Bruce.

More changes to the suser() API will come along with the "jail" code.

Use suser() to check for super user rather than examining cr_uid directly.
Use TTYDEF_SPEED rather than 9600 a couple of places.

Reviewed by: bde, with a few grumbles.

Initialize isa_devtab entries for interrupt handlers in individual
device drivers, not in ioconf.c. Use a different hack in isa_device.h
so that a new config(8) is not required yet.

pc98 parts approved by: kato

fix handling more than one cards
Submitted by: "Sergey V.Dorokhov" <svd@kbtelecom.nalnet.ru>

Added D_TTY to the cdevswitch flags for all tty drivers. This is required
for the Lite2 fix for always returning EIO in dead_read().

Cleaned up the cdevswitch initializers for all tty drivers.

Removed explicit calls to ttsetwater() from all (tty) drivers. ttsetwater()
is now called centrally for opens, not just for parameter changes.

Register tty software interrupt handlers at run time using register_swi()
instead of at compile time using ifdefs.

Use _swi_null instead of dummycamisr. CAM and dpt should call
register_swi() instead of hacking on ihandlers[] directly.

Fixed null setting of multiple wakeup prevention variable.

Fixed printf format errors.

This commit fixes various 64bit portability problems required for
FreeBSD/alpha. The most significant item is to change the command
argument to ioctl functions from int to u_long. This change brings us
inline with various other BSD versions. Driver writers may like to
use (__FreeBSD_version == 300003) to detect this change.

The prototype FreeBSD/alpha machdep will follow in a couple of days
time.

Implement the spirit but not the letter of Terrys hot-char patch.

The differences Terrys patch and this patch are:
* Remove a lot of un-needed comments.
* Don't put l_hotchar at the front of stuct linesw, there is no need to.
* Use the #defines for the hotchar in the SLIP and PPP line disciplines

Make all file-system (MFS, FFS, NFS, LFS, DEVFS) related option new-style.

This introduce an xxxFS_BOOT for each of the rootable filesystems.
(Presently not required, but encouraged to allow a smooth move of option *FS
to opt_dontuse.h later.)

LFS is temporarily disabled, and will be re-enabled tomorrow.

Use ENOIOCTL instead of -1 (= ERESTART) for tty ioctls that are
not handled at a particular level. This fixes mainly restarting
of interrupted TIOCDRAINs and TIOCSETA{W,F}s.

Update select -> poll in drivers.

Removed unused #includes.

Don't depend on gcc's feature of permitting labels that aren't followed
by a statement.

Don't include <sys/ioctl.h> in the kernel. Stage 1: don't include
it when it is not used. In most cases, the reasons for including it
went away when the special ioctl headers became self-sufficient.

Don't #include <sys/fcntl.h> in <sys/file.h> if KERNEL is defined.
Fixed everything that depended on getting fcntl.h stuff from the wrong
place. Most things don't depend on file.h stuff at all.

Remove SC_KBD_PROBE_WORKS option and replace it with a simple run-time flag
bit (0x0008) in the sc driver configuration line. This way it's easy to
boink a generic kernel.

Also, document and place in an opt_ file the #define's for overriding which
serial port is the system console.
Approved by: sos

Remove devconf, it never grew up to be of any use.

Removed unused #includes of <i386/isa/icu.h> and <i386/isa/icu.h>. icu.h
is only used by the icu support modules and by a few drivers that know
too much about the icu (most only use it to convert `n' to `IRQn'). isa.h
is only used by ioconf.c and by a few drivers that know too much about
isa addresses (a few have to, because config is deficient).

Clean up -Wunused warnings.

Reviewed by: bde

Switched from using devfs_add_sw() to using devfs_add_swf()

Reviewed by: julian@freebsd.org

Convert a timeout loop from 100 iterations of 15uS to 50
iterations of 30uS so that really fast systems stop getting
timeout messages from the Riscom driver.

Reviewed by: ache, peter@nmti.com (Peter da Silva)

Add more disc_optim calls to track line disc changes

Replaced nxreset by noreset (if the reset function gets called, then the
device must be configured. It's hard to tell whether a reset function
should be noreset or nullreset since reset functions are never called.
Most drivers use nullreset but noreset has the advantage of complaining
if somehow gets called).

Removed new alias d_size_t for d_psize_t.

Removed old aliases d_rdwr_t and d_ttycv_t for d_read_t/d_write_t and
d_devtotty_t.

Sorted declarations of switch functions into switch order.

Removed duplicated comments and declarations of nonexistent switch
functions.

Staticize and cleanup.

Julian forgot to make the *devsw structures static.

Pass 3 of the great devsw changes
most devsw referenced functions are now static, as they are
in the same file as their devsw structure. I've also added DEVFS
support for nearly every device in the system, however
many of the devices have 'incorrect' names under DEVFS
because I couldn't quickly work out the correct naming conventions.
(but devfs won't be coming on line for a month or so anyhow so that doesn't
matter)

If you "OWN" a device which would normally have an entry in /dev
then search for the devfs_add_devsw() entries and munge to make them right..
check out similar devices to see what I might have done in them in you
can't see what's going on..
for a laugh compare conf.c conf.h defore and after... :)
I have not doen DEVFS entries for any DISKSLICE devices yet as that will be
a much more complicated job.. (pass 5 :)

pass 4 will be to make the devsw tables of type (cdevsw * )
rather than (cdevsw)
seems to work here..
complaints to the usual places.. :)

Removed unnecessary #includes of <sys/user.h>. Some of these were just
to get the definitions of TRUE and FALSE which happen to be defined in
a deeply nested include.

Added nearby #includes of <sys/conf.h> where appropriate.

If you're going to mechanically replicate something in 50 files
it's best to not have a (compiles cleanly) typo in it! (sigh)

OK, that's it..
That's EVERY SINGLE driver that has an entry in conf.c..
my next trick will be to define cdevsw[] and bdevsw[]
as empty arrays and remove all those DAMNED defines as well..

Each of these drivers has a SYSINIT linker set entry
that comes in very early.. and asks teh driver to add it's own
entry to the two devsw[] tables.

some slight reworking of the commits from yesterday (added the SYSINIT
stuff and some usually wrong but token DEVFS entries to all these
devices.

BTW does anyone know where the 'ata' entries in conf.c actually reside?
seems we don't actually have a 'ataopen() etc...

If you want to add a new device in conf.c
please make sure I know
so I can keep it up to date too..

as before, this is all dependent on #if defined(JREMOD)
(and #ifdef DEVFS in parts)

the second set of changes in a move towards getting devices to be
totally dynamic.

this is only the devices in i386/isa
I'll do more tomorrow.
they're completely masked by #ifdef JREMOD at this stage...
the eventual aim is that every driver will do a SYSINIT
at startup BEFORE the probes, which will effectively
link it into the devsw tables etc.

If I'd thought about it more I'd have put that in in this set (damn)
The ioconf lines generated by config will also end up in the
device's own scope as well, so ioconf.c will eventually be gutted
the SYSINIT call to the driver will include a phase where the
driver links it's ioconf line into a chain of such. when this phase is done
then the user can modify them with the boot: -c
config menu if he wants, just like now..
config will put the config lines out in the .h file
(e.g. in aha.h will be the addresses for the aha driver to look.)
as I said this is a very small first step..
the aim of THIS set of edits is to not have to edit conf.c at all when
adding a new device.. the tabe will be a simple skeleton..

when this is done, it will allow other changes to be made,
all teh time still having a fully working kernel tree,
but the logical outcome is the complete REMOVAL of the devsw tables.

By the end of this, linked in drivers will be exactly the same as
run-time loaded drivers, except they JUST HAPPEN to already be linked
and present at startup..
the SYSINIT calls will be the equivalent of the "init" call
made to a newly loaded driver in every respect.

For this edit,
each of the files has the following code inserted into it:

obviously, tailored to suit..
----------------------somewhere at the top:
#ifdef JREMOD
#include <sys/conf.h>
#define CDEV_MAJOR 13
#define BDEV_MAJOR 4
static void sd_devsw_install();
#endif /*JREMOD */
---------------------somewhere that's run during bootup: EVENTUALLY a SYSINIT
#ifdef JREMOD
sd_devsw_install();
#endif /*JREMOD*/
-----------------------at the bottom:
#ifdef JREMOD
struct bdevsw sd_bdevsw =
{ sdopen, sdclose, sdstrategy, sdioctl, /*4*/
sddump, sdsize, 0 };

struct cdevsw sd_cdevsw =
{ sdopen, sdclose, rawread, rawwrite, /*13*/
sdioctl, nostop, nullreset, nodevtotty,/* sd */
seltrue, nommap, sdstrategy };

static sd_devsw_installed = 0;

static void sd_devsw_install()
{
dev_t descript;
if( ! sd_devsw_installed ) {
descript = makedev(CDEV_MAJOR,0);
cdevsw_add(&descript,&sd_cdevsw,NULL);
#if defined(BDEV_MAJOR)
descript = makedev(BDEV_MAJOR,0);
bdevsw_add(&descript,&sd_bdevsw,NULL);
#endif /*BDEV_MAJOR*/
sd_devsw_installed = 1;
}
}
#endif /* JREMOD */

Added `#include "ioconf.h"' to <machine/conf.h> and cleaned up the
misplaced extern declarations (mostly prototypes of interrupt handlers)
that this exposed. The prototypes should be moved back to the driver
sources when the functions are staticalized.

Added idempotency guards to <machine/conf.h>. "ioconf.h" can't be
included when building LKMs so define a wart in bsd.kmod.mk to help
guard against including it.

Moved prototypes for devswitch functions from conf.c and driver sources
to <machine/conf.h>. conf.h was mechanically generated by
`grep ^d_ conf.c >conf.h'. This accounts for part of its ugliness. The
prototypes should be moved back to the driver sources when the functions
are staticalized.

Allow any speed from 0..76800
Reviewed by:
Submitted by:
Obtained from:

Improve input flow control.

Use input buffer watermarks of TTYHOG-512 (high) and (high)*7/8
(low) instead of TTYHOG/2 (high) and TTYHOG/5 (low) to agree with
some drivers. 512 is magic and some things depended on TTYHOG/2
>= TTYHOG-512 to work; now they depend on the 512 magic not changing
and TTYHOG-512 being significantly larger than 0. This should be
handled in ttsetwater().

Separate the decision about whether to do input flow control from
doing it. ttyblock() now just starts input flow control (hardware
and/or software) and there is a new function ttyunblock() to stop
it. The decisions are the same except for the watermark changes
and allowing for input expansion for PARMRK.

When flushing input, try harder at first to send a start character
if required, but give up if the first attempt fails.

cy.c, rc.c, sio.c:
Simplify: let ttyinput() handle input flow control if it is not
being bypassed. Use ttyblock() to start flow control otherwise.

rc.c:
Use same input flow control test as elsewhere: test in a more
efficient order and start flow control at >= highwater instead of
at > highwater.

Don't let IXOFF or ECHONL stop the setting of TS_CAN_BYPASS_L_RINT. IXOFF
is handled at a low level, and ECHONL only applies if ICANON is set,
although tty.c sometimes bogusly applies it when ICANON isn't set.

Always wake up writers after clearing TS_BUSY. This will soon be
essential when I fix excessive wakeups for output-below-low-water.
In cy.c and sio.c, wake up via the driver start routine to also
eliminate duplicated code involving the clearing of TS_TTSTOP.

Always (except in code to be replaced soon) call driver start
routine directly instead of going through ttstart().

Obtained from: partly from ancient patches of mine via 1.1.5

Give names to the magic tty i/o sleep addresses and use them. This makes
it easier to remember what the addresses are for and to keep them unique.

Move the inline code for waking up writers to a new function
ttwwakeup(). The conditions for doing the wakeup will soon become
more complicated and I don't want them duplicated in all drivers.

It's probably not worth making ttwwakeup() a macro or an inline
function. The cost of the function call is relatively small when
there is a process to wake up. There is usually a process to wake
up for large writes and the system call overhead dwarfs the function
call overhead for small writes.

Next version, many bugs fixed

RISCom/8 driver