- Enable keyboard autodetection by default for ISA syscons attachments.
- If there are no syscons hints at all, assume there is a single sc0 device
anyway. The console probe will still fail unless a VGA adapter is found.
MFC after: 2 weeks
- An "at" hint now reserves a device name.
- A new BUS_HINT_DEVICE_UNIT method is added to the bus interface. When
determining the unit number of a device, this method is invoked to
let the bus driver specify the unit of a device given a specific
devclass. This is the only way a device can be given a name reserved
via an "at" hint.
- Implement BUS_HINT_DEVICE_UNIT() for the acpi(4) and isa(4) bus drivers.
Both of these busses implement this by comparing the resources for a
given hint device with the resources enumerated by ACPI/PnPBIOS and
wire a unit if the hint resources are a subset of the "real" resources.
- Use bus_hinted_children() for adding hinted devices on isa(4) busses
now instead of doing it by hand.
- Remove the unit kludging from sio(4) as it is no longer necessary.
Prodding from: peter, imp
OK'd by: marcel
MFC after: 1 month
Make the ISA bus keep track of more PNP details. Plus a minor style
fix while I'm here. More could be done here, but except for some SBCs
that don't have ACPI, there's limited value to anybody in doing so.
Make clock_if.m and subr_rtc.c standard on i386
Add hints for "atrtc" driver, for non-PnP, non-ACPI systems.
NB: Make sure to install GENERIC.hints into /boot/device.hints in these!
Nuke MD inittodr(), resettodr() functions.
Don't attach to PHP0B00 in the "attimer" dummy driver any more, and remove
comments that no longer apply for that reason.
Add new "atrtc" device driver, which handles IBM PC AT Real Time
Clock compatible devices using subr_rtc and clock_if.
This driver is not entirely clean: other code still fondles the
hardware to get a statclock interrupt on non-ACPI timer systems.
Wrap some overly long lines.
After it has settled in -current, this will be ported to amd64.
Technically this is MFC'able, but I fail to see a good reason.
frequency generation and what frequency the generated was anyones
guess.
In general the 32.768kHz RTC clock x-tal was the best, because that
was a regular wrist-watch Xtal, whereas the X-tal generating the
ISA bus frequency was much lower quality, often costing as much as
several cents a piece, so it made good sense to check the ISA bus
frequency against the RTC clock.
The other relevant property of those machines, is that they
typically had no more than 16MB RAM.
These days, CPU chips croak if their clocks are not tightly within
specs and all necessary frequencies are derived from the master
crystal by means if PLL's.
Considering that it takes on average 1.5 second to calibrate the
frequency of the i8254 counter, that more likely than not, we will
not actually use the result of the calibration, and as the final
clincher, we seldom use the i8254 for anything besides BEL in
syscons anyway, it has become time to drop the calibration code.
If you need to tell the system what frequency your i8254 runs,
you can do so from the loader using hw.i8254.freq or using the
sysctl kern.timecounter.tc.i8254.frequency.
The timer_spkr_*() functions take care of the enabling/disabling
of the speaker.
Test on the existence of timer_spkr_*() functions, rather than
architectures.
these days, so de-generalize the acquire_timer/release_timer api
to just deal with speakers.
The new (optional) MD functions are:
timer_spkr_acquire()
timer_spkr_release()
and
timer_spkr_setfreq()
the last of which configures the timer to generate a tone of a given
frequency, in Hz instead of 1/1193182th of seconds.
Drop entirely timer2 on pc98, it is not used anywhere at all.
Move sysbeep() to kern/tty_cons.c and use the timer_spkr*() if
they exist, and do nothing otherwise.
Remove prototypes and empty acquire-/release-timer() and sysbeep()
functions from the non-beeping archs.
This eliminate the need for the speaker driver to know about
i8254frequency at all. In theory this makes the speaker driver MI,
contingent on the timer_spkr_*() functions existing but the driver
does not know this yet and still attaches to the ISA bus.
Syscons is more tricky, in one function, sc_tone(), it knows the hz
and things are just fine.
In the other function, sc_bell() it seems to get the period from
the KDMKTONE ioctl in terms if 1/1193182th second, so we hardcode
the 1193182 and leave it at that. It's probably not important.
Change a few other sysbeep() uses which obviously knew that the
argument was in terms of i8254 frequency, and leave alone those
that look like people thought sysbeep() took frequency in hertz.
This eliminates the knowledge of i8254_freq from all but the actual
clock.c code and the prof_machdep.c on amd64 and i386, where I think
it would be smart to ask for help from the timecounters anyway [TBD].
implemented with macros. This patch improves code readability. Reasoning
behind vidd_* is a sort of "video discipline".
List of macros is supposed to be complete--all methods of video_switch
ought to have their respective macros from now on.
Functionally, this code should be no-op. My intention is to leave current
behaviour of touched code as is.
No objections: rwatson
Silence on: freebsd-current@
Approved by: cognet
refactored it to be a generic device.
Instead of being part of the standard kernel, there is now a 'nvram' device
for i386/amd64. It is in DEFAULTS like io and mem, and can be turned off
with 'nodevice nvram'. This matches the previous behavior when it was
first committed.
day of week field correctly, or they remember bad values that are
written into the day of week field. For this reason, ignore the day
of week field when reading the clock on i386 rather than bailing if
it is set incorrectly.
Problems were seen on a number of platforms, including VMWare, qemu,
EPIA ME6000, Epox-3PTA and ABIT-SL30T.
This is a slightly different fix to that proposed by Ted in his PR,
but the same basic idea.
PR: 111117
Submitted by: Ted Faber <faber@lunabase.org>
Approved by: re (rwatson)
MFC after: 3 weeks
print a one line error message. Add some comments on not being able to
trust the day of week field (I'll act on these comments in a follow up
commit).
Approved by: re
MFC after: 3 weeks
114 bytes of cmos ram in the PC clock chip. The big difference between
this and the Linux version is that we do not recalculate the checksums
for bytes 16..31.
We use this at work when cloning identical machines - we can copy the
bios settings as well. Reading /dev/nvram gives 114 bytes of data but
you can seek/read/write whichever bytes you like.
Yes, this is a "foot, gun, fire!" type of device.
sysctl_handle_int is not sizeof the int type you want to export.
The type must always be an int or an unsigned int.
Remove the instances where a sizeof(variable) is passed to stop
people accidently cut and pasting these examples.
In a few places this was sysctl_handle_int was being used on 64 bit
types, which would truncate the value to be exported. In these
cases use sysctl_handle_quad to export them and change the format
to Q so that sysctl(1) can still print them.
to move up the start address until the allocation succeeds. If the
alignment of the resource was 0, then the code would keep trying the same
request in an infinite loop and hang. Force the request to always move
start up by at least 1 byte each time through the loop.
RTC state, then it may clobber the RTC index register, so the index
register must be restored before using it to restore control registers
in rtc_restore().
The following problems remain:
- rtc_restore() is only called if pmtimer is configured. Buggy
suspend/resumes are more likely to clobber the index register than
a control register, so pmtimer is more needed than it used to be.
- pmtimer doesn't exist for amd64.
- Restoring of the RTC state may race with rtcintr(). If an RTC
interrupt is handled before the state is restored, then rtcin(RTC_INTR)
in rtcintr() may read from the wrong register, so rtcintr() may spin
forever. This may be mitigated by the most common state clobbering
being to turn off RTC interrupts.
used by clock code, so don't export it to the world for machdep.c to
initialize. There is a minor problem initializing it before it is
used, since although clock initialization is split up so that parts
of it can be done early, the first part was never done early enough
to actually work. Split it up a bit more and do the first part as
late as possible to document the necessary order. The functions that
implement the split are still bogusly exported.
Cleaned up initialization of the i8254 clock hardware using the new
split. Actually initialize it early enough, and don't work around it
not being initialized in DELAY() when DELAY() is called early for
initialization of some console drivers.
This unfortunately moves a little more code before the early debugger
breakpoint so that it is harder to debug. The ordering of console and
related initialization is delicate because we want to do as little as
possible before the breakpoint, but must initialize a console.
and by only delaying when an RTC register is written to. The delay
after writing to the data register is now not just a workaround.
This reduces the number of ISA accesses in the usual case from 4 to
1. The usual case is 2 rtcin()'s for each RTC interrupt. The index
register is almost always RTC_INTR for this. The 3 extra ISA accesses
were 1 for writing the index and 2 for delays. Some delays are needed
in theory, but in practice they now just slow down slow accesses some
more since almost eveyone including us does them wrong so modern systems
enforce sufficient delays in hardware. I used to have the delays ifdefed
out, but with the index register optimization the delays are rarely
executed so the old magic ones can be kept or even implemented non-
magically without significant cost.
Optimizing RTC interrupt handling is more interesting than it used to
be because RTC interrupts are currently needed to fix the more efficient
apic timer interrupts on some systems. apic_timer_hz is normally 2000
so the RTC interrupt rate needs to be 2048 to keep the apic timer
firing on such systems. Without these changes, each RTC interrupt
normally took 10 ISA accesses (2 PIC accesses and 2 sets of 4 RTC
accesses). Each ISA access takes 1-1.5uS so 10 of then at 2048 Hz
takes 2-3% of a CPU. Now 4 of them take 0.8-1.2% of a CPU.
Split subr_clock.c in two parts (by repo-copy):
subr_clock.c contains generic RTC and calendaric stuff. etc.
subr_rtc.c contains the newbus'ified RTC interface.
Centralize the machdep.{adjkerntz,disable_rtc_set,wall_cmos_clock}
sysctls and associated variables into subr_clock.c. They are
not machine dependent and we have generic code that relies on being
present so they are not even optional.
atkbd. Version 1.162 of GENERIC fixed this problem in April of 1999.
Subsequent to that, the hints data was removed from GENERIC and move
to hints files. All the hints file ever created have atkbd at the
right location. This should have been removed just after RELENG_4 was
branched (and likely around 4.5 in RELENG_4).
MFC After: 3 days
for CBUS-PNP cards there) by default, as there are no amd64 and sparc64
machines with ISA slots and which therefore could make use of this code
known to exist. For sparc64 this additionally allows to get rid of the
compat shims for in{b,w,l}()/out{b,w,l}() etc and the associated hacks.
OK'ed by: imp, peter
passing a pointer to an opaque clockframe structure and requiring the
MD code to supply CLKF_FOO() macros to extract needed values out of the
opaque structure, just pass the needed values directly. In practice this
means passing the pair (usermode, pc) to hardclock() and profclock() and
passing the boolean (usermode) to hardclock_cpu() and hardclock_process().
Other details:
- Axe clockframe and CLKF_FOO() macros on all architectures. Basically,
all the archs were taking a trapframe and converting it into a clockframe
one way or another. Now they can just extract the PC and usermode values
directly out of the trapframe and pass it to fooclock().
- Renamed hardclock_process() to hardclock_cpu() as the latter is more
accurate.
- On Alpha, we now run profclock() at hz (profhz == hz) rather than at
the slower stathz.
- On Alpha, for the TurboLaser machines that don't have an 8254
timecounter, call hardclock() directly. This removes an extra
conditional check from every clock interrupt on Alpha on the BSP.
There is probably room for even further pruning here by changing Alpha
to use the simplified timecounter we use on x86 with the lapic timer
since we don't get interrupts from the 8254 on Alpha anyway.
- On x86, clkintr() shouldn't ever be called now unless using_lapic_timer
is false, so add a KASSERT() to that affect and remove a condition
to slightly optimize the non-lapic case.
- Change prototypeof arm_handler_execute() so that it's first arg is a
trapframe pointer rather than a void pointer for clarity.
- Use KCOUNT macro in profclock() to lookup the kernel profiling bucket.
Tested on: alpha, amd64, arm, i386, ia64, sparc64
Reviewed by: bde (mostly)
nearly identical to wintel/ia32, with a couple of tweaks. Since it is
so similar to ia32, it is optionally added to a i386 kernel. This
port is preliminary, but seems to work well. Further improvements
will improve the interaction with syscons(4), port Linux nforce driver
and future versions of the xbox.
This supports the 64MB and 128MB boxes. You'll need the most recent
CVS version of Cromwell (the Linux BIOS for the XBOX) to boot.
Rink will be maintaining this port, and is interested in feedback.
He's setup a website http://xbox-bsd.nl to report the latest
developments.
Any silly mistakes are my fault.
Submitted by: Rink P.W. Springer rink at stack dot nl and
Ed Schouten ed at fxq dot nl
on big-endian archs like sparc64, e.g.:
uart0: <16550 or compatible> at port 0x3f8-0x3ff irq 43 pnpid @HEd041 on isa0
is now correctly printed as:
uart0: <16550 or compatible> at port 0x3f8-0x3ff irq 43 pnpid PNP0501 on isa0
There are probably other endianness issues lurking in the PnP code which
however aren't exhibited on sparc64 as the PnP devices there are sort of
PnP BIOS devices rather than ISA PnP devices.
Tested on: i386, sparc64
MFC after: 1 week
primary vendor id for this device. The location is empty because ISA
doesn't give one a way to generally locate a card. PNP BIOS entries
do provide a way to locate cards, as do isa pnp cards. These
locations will be added as soon as the code to remember them is
written.
- Make sure timer0_max_count is set to a correct value in the lapic case.
- Revert i8254_restore() to explicitly reprogram timer 0 rather than
calling set_timer_freq() to do it. set_timer_freq() only reprograms
the counter if the max count changes which it never does on resume. This
unbreaks suspend/resume for several people.
Tested by: marks, others
Reviewed by: bde
MFC after: 3 days
copied and pasted. I had actually tested without this change in my
trees as had the other testers.
Reported by: bde, Rostislav Krasny rosti dot bsd at gmail dot com
Approved by: re (scottl)
Pointy hat to: jhb
timer since irq0 isn't being driven at hz in that case and we don't need to
try to handle edge cases with rollover, etc. that require irq0 to be firing
for the timecounter to actually work.
Submitted by: phk
Tested by: schweikh
Approved by: re (scottl)
files after they were repo-copied to sys/dev/atkbdc. The sources of
atkbdc(4) and its children were moved to the new location in preparation
for adding an EBus front-end to atkbdc(4) for use on sparc64; i.e. in
order to not further scatter them over the whole tree which would have
been the result of adding atkbdc_ebus.c in e.g. sys/sparc64/ebus. Another
reason for the repo-copies was that some of the sources were misfiled,
e.g. sys/isa/atkbd_isa.c wasn't ISA-specific at all but for hanging
atkbd(4) off of atkbdc(4) and was renamed to atkbd_atkbdc.c accordingly.
Most of sys/isa/psm.c, i.e. expect for its PSMC PNP part, also isn't
ISA-specific.
- Separate the parts of atkbdc_isa.c which aren't actually ISA-specific
but are shareable between different atkbdc(4) bus front-ends into
atkbdc_subr.c (repo-copied from atkbdc_isa.c). While here use
bus_generic_rl_alloc_resource() and bus_generic_rl_release_resource()
respectively in atkbdc_isa.c instead of rolling own versions.
- Add sparc64 MD bits to atkbdc(4) and atkbd(4) and an EBus front-end for
atkbdc(4). PS/2 controllers and input devices are used on a couple of
Sun OEM boards and occur on either the EBus or the ISA bus. Depending on
the board it's either the only on-board mean to connect a keyboard and
mouse or an alternative to either RS232 or USB devices.
- Wrap the PSMC PNP part of psm.c in #ifdef DEV_ISA so it can be compiled
without isa(4) (e.g. for EBus-only machines). This ISA-specific part
isn't separated into its own source file, yet, as it requires more work
than was feasible for 6.0 in order to do it in a clean way. Actually
philip@ is working on a rewrite of psm(4) so a more comprehensive
clean-up and separation of hardware dependent and independent parts is
expected to happen after 6.0.
Tested on: i386, sparc64 (AX1105, AXe and AXi boards)
Reviewed by: philip
i8253reg.h, and add some defines to control a speaker.
- Move PPI related defines from i386/isa/spkr.c into ppireg.h and use them.
- Move IO_{PPI,TIMER} defines into ppireg.h and timerreg.h respectively.
- Use isa/isareg.h rather than <arch>/isa/isa.h.
Tested on: i386, pc98
Instead, explicitly enable them when we setup the interrupt handler.
Also, move the setting of stathz and profhz down to the same place so
that the code flow is simpler and easier to follow.
- Don't setup an interrupt handler for IRQ0 if we are using the lapic timer
as it doesn't do anything productive in that case.
last in the list rather than first.
This makes the resouces print in the 4.x order rather than the 5.x order
(eg fdc0 at 0x3f0-0x3f5,0x3f7 is 4.x, but 0x3f7,0x3f0-0x3f5 is 5.x). This
also means that the pci code will once again print the resources in BAR
ascending order.
is particularly useful when VESA is available (either `options VESA'
or load the vesa module), as BIOSes in some notebooks may correctly
save and restore LCD panel settings using VESA in cases where calling
the video BIOS POST is not effective. On some systems it may also
be necessary to set the hw.acpi.reset_video sysctl to 0.
rather than forwarding interrupts from the clock devices around using IPIs:
- Add an IDT vector that pushes a clock frame and calls
lapic_handle_timer().
- Add functions to program the local APIC timer including setting the
divisor, and setting up the timer to either down a periodic countdown
or one-shot countdown.
- Add a lapic_setup_clock() function that the BSP calls from
cpu_init_clocks() to setup the local APIC timer if it is going to be
used. The setup uses a one-shot countdown to calibrate the timer. We
then program the timer on each CPU to fire at a frequency of hz * 3.
stathz is defined as freq / 23 (hz * 3 / 23), and profhz is defined as
freq / 2 (hz * 3 / 2). This gives the clocks relatively prime divisors
while keeping a low LCM for the frequency of the clock interrupts.
Thanks to Peter Jeremy for suggesting this approach.
- Remove the hardclock and statclock forwarding code including the two
associated IPIs. The bitmap IPI handler has now effectively degenerated
to just IPI_AST.
- When the local APIC timer is used we don't turn the RTC on at all, but
we still enable interrupts on the ISA timer 0 (i8254) for timecounting
purposes.
uses the i8237 without trying to emulate the PC architecture move
the register definitions for the i8237 chip into the central include
file for the chip, except for the PC98 case which is magic.
Add new isa_dmatc() function which tells us as cheaply as possible
if the terminal count has been reached for a given channel.
interrupts, read from the interrupt status register to clear any pending
interrupts. Otherwise in some rare cases the RTC would never fire any
interrupts as it constantly thinks it has an interrupt pending.
PR: i386/17800
PR: kern/76776
Submitted by: Jose M. Alcaide jose at we dot lc dot ehu dot es
MFC after: 2 weeks
have seen in the isa pnp case where a resource buts up against
0xffffffff. This would only impact when the board was booted without
ACPI.
Submitted by: Ed Maste (freebsd-stable <20050103145720.GA90754@sandvine.com>)
MFC After: 5 days
o Implement a shiny new algorithm to keep track of finger movement at
slow speeds. This dramatically reduces the level of questionable
language from users trying to resize windows.
o Properly catch the many extra buttons and dials which manufacturers
are known to screw onto Synaptics touchpad controllers. Currently,
up to seven buttons are known to work, more should work too.
o Add a number of sysctls allowing one to tune the driver to taste in
a simple way:
# Should the extra buttons act as axes or as middle button
hw.psm.synaptics.directional_scrolls
# These control the 'stickiness' at low speeds
hw.psm.synaptics.low_speed_threshold
hw.psm.synaptics.min_movement
hw.psm.synaptics.squelch_level
PR: kern/75725
Submitted by: Jason Kuri <jay@oneway.com>
MFC after: 1 month
o Move the sysctls under debug.psm.* and hw.psm.* making them a bit
clearer and more consistent with other drivers.
o Remove the debug.psm_soft_timeout sysctl. It was introduced many
moons ago in r1.64 but never referenced anywhere.
o Introduce hw.psm.tap_threshold and hw.psm.tap_timeout to control
the behaviour of taps on touchpads. People might like to fiddle
with these if tapping seems to slow or too fast for them.
o Add debug.psm.loglevel as a tunable so that verbosity can be set
easily at boot-time (to watch probes and such) without having to
compile a kernel with options PSM_DEBUG=N.
These devices should be probed first because they are at fixed
locations and cannot be turned off. ISA PNP devices, on the other
hand, can be turned off and often can be flexible in the resources
they use. Probe them last, as always.
people have reported problems (stickyness, aiming difficulty) which is proving
difficult to fix, so this will default to disable until sometime after 5.3R.
To enable Synaptics support, set the 'hw.psm.synaptics_support=1' tunable.
MT5 candidate.
Approved by: njl
because it was mostly irrelevant - except for the silly BIOS_PADDRTOVADDR
etc macros. Along the way of working around this, I missed a few things.
* Make syscons properly inherit the bios capslock/shiftlock/etc state like
i386 does. Note that we cannot inherit the bios key repeat rate because
that requires a bios call (which is impossible for us).
* Give syscons the ability to beep on amd64. Oops.
While here, make bios.c compile and add it to files.amd64.
and which takes a M_WAITOK/M_NOWAIT flag argument.
Add compatibility isa_dmainit() macro which whines loudly if
isa_dma_init() fails.
Problem uncovered by: tegge
o Remove PSM_SYNCERR_THRESHOLD1. This value specified how many sync
errors were required before the mouse is re-initialised.
Re-initialisation is now done after (packetsize * 2) sync errors as
things aren't likely to improve after that.
o Reset lastinputerror when re-initialisation occurs. We don't want
to continue to drop data after re-initialisation.
o Count the number of failed packets independently of the syncerrors
statistic. syncerrors is useful for recovering sync within a single
packet. pkterrors allows us to detect when the mouse changes its
packet mode due to some external event (e.g. KVM switch).
o Reinitialize the mouse if we see more than psmpkterrthresh errors
during the validation period. The validation period begins as soon
as a sync error is detected and continues until psmerrsecs/msecs
time has elapsed. The defaults for these two values force a reset
if we see two packet errors in a 2 second period. This allows rapid
detection of packet framing errors caused by the mouse changing packet
modes.
o Export psmpkterrthresh as a sysctl
o Export psmloglevel as a sysctl.
o Enable more debugging code to be enabled at runtime via psmloglevel.
o Simplify verbose conditioned loging by using a VLOG macro.
o Add several comments describing the sync recovery algorithm of
this driver.
Large Portions by: Brian Somers <brian@Awfulhak.org>
Inspired and Frustrated by: Belkin KVMs
Reviewed by: njl, philip
data packet is received from the mouse. In the case of many KVM's,
this avoids a bug in their mouse emulation that sends back incorrect
sync when you explicitly request a data packet from the mouse. Without
this change, you must force the driver into stock PS/2 mode or be flooded
with a never ending stream of "out of sync" messages on these KVMs.
Approved by: re
o Change the motion calculation to result in
a more reasonable speed of motion
This should fix the 'aiming' problems people have reported. It also
mitigates (but doesn't completely solve) the 'stalling' problems at
very low speeds.
Tested by: many subscribers to -current
Approved by: njl
o Catch 'taps' as button presses
o One finger sends button1, two fingers send button3,
three fingers send button2 (double-click)
Tested by: many subscribers to -current
Approved by: njl
o Handle the 'up/down' buttons some touchpads have as
a z-axis (scrollwheel) as recommended by the specs
o Report the buttons as button4 and button5 instead
of button2 and button4, button2 can be emulated by
pressing button1 and button3 simultaneously. This
allows one to use the two extra buttons for other
purposes if one so desires.
Tested by: many subscribers to -current
Approved by: njl
o Clean up whitespace and comments in the
enable_synaptics() probing function
o Only use (and rely on) the extended capability
bits when we are told they actually exist
o Partly ignore the (possibly dated?) part of the
specification about the mode byte so that we
can support 'guest devices' too.
Tested by: many subscribers to -current
Approved by: njl
submitted version with style cleanups and changes to comments. I also
modified the ioctl interface. This version only has one ioctl (to get
the Synaptics-specific config parameters) since this is the only
information a user might want.
Submitted by: Arne Schwabe <arne -at- rfc2549.org>
a problem that could also be fixed differently without reverting previous
attempts to fix DELAY while the debugger is active (rev 1.204). The bug
was that the i8254 implements a countdown timer, while for (k)db_active
a countup timer was implemented. This resulted in premature termination
and consequently the breakage of DELAY. The fix (relative to rev 1.211)
is to implement a countdown timer for the kdb_active case. As such the
ability to step clock initialization is preserved and DELAY does what is
expected of it.
Blushed: bde :-)
Submitted by: bde
debugger is not active. The fixes breakages of DELAY() when
running in the debugger, because not calling getit() when the
debugger is active yields a DELAY that doesn't.
repocopied. Soon there will be additional bus attachments and
specialization for isa, acpi and pccard (and maybe pc98's cbus).
This was approved by nate, joerg and myself. bde dissented on the new
location, but appeared to be OK after some discussion.
correct interrupt source.
- Cache a pointer to the i8254_intsrc's pending method to avoid several
pointer indirections in i8254_get_timecount().
Reported by: bde
