PPS events must be recorded according to PPS's mode settings.
If a process asks for (i.e.) capture-assert events only, when the PPS
client calls the pps_event() function to save the current PPS event, we
should verify the event type and then discard unwanted ones.
Also, without this patch userland processes waiting for a specific PPS
event (assert or clear but not both) may be awakened at wrong time.
Signed-off-by: Rodolfo Giometti <giometti@linux.it>
Tested-by: William S. Brasher <billb958@door.net>
Tested-by: Reg Clemens <clemens@dwf.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Userland programs may read/write PPS parameters at same time and these
operations may corrupt PPS data.
Signed-off-by: Rodolfo Giometti <giometti@linux.it>
Tested-by: Reg Clemens <clemens@dwf.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
TASK_INTERRUPTIBLE and friends are now only available after including
<linux/sched.h>, so include it when needed.
bus_id is no longer available/necessary, so remove that.
Android pmem driver is not available in mainline, so remove its hooks
from drivers/video.
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In case of failure, device_create() returns not NULL but the error code.
The current code checks for non-NULL though which causes kernel oops in
sysfs_create_group() when device_create() fails. Check for error using
IS_ERR() and propagate the error value using PTR_ERR() instead of fixed
-ENODEV code returned now...
Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
v3020_mmio_read_bit() always returns 0 when left_shift > 7.
v3020_mmio_read_bit()'s return type is (unsigned char). The code returns
a value masked by (1 << left_shift) that is casted to the return type. If
left_shift is larger than 7, the cast will always result in a 0 return
value. The problem was discovered with left_shift = 16, and the included
patch corrects the problem.
The bug was introduced in the last (Apr 3 2009) commit of the file, kernel
versions 2.6.30 and later.
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Raphael Assenat <raph@8d.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/rtc/rtc-vr41xx.c: In function 'vr41xx_rtc_irq_set_freq':
drivers/rtc/rtc-vr41xx.c:217: warning: comparison of distinct pointer types lacks a cast
drivers/rtc/rtc-vr41xx.c:217: warning: right shift count >= width of type
drivers/rtc/rtc-vr41xx.c:217: warning: passing argument 1 of '__div64_32' from incompatible pointer type
include/asm-generic/div64.h:35: note: expected 'uint64_t *' but argument is of type 'long unsigned int *'
Signed-off-by: Yoichi Yuasa <yuasa@linux-mips.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The config FB_PRE_INIT_FB entry in drivers/video/Kconfig pushes all entries
below it out of the menuconfig selection. Fix this.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This seems to be a different model (with a different PCI ID) than the
"Quatro" card that is also in the list.
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
struct uart_port::iobase is unsigned long, so use %lx as printk format
specifier.
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
According to Documentation/rtc.txt, RTC_WKALM_SET sets the alarm time and
enables/disables the alarm. We implement RTC_WKALM_SET through
pcf50633_rtc_set_alarm. The enabling/disabling part was missing.
Signed-off-by: Werner Almesberger <werner@openmoko.org>
Reported-by: Michael 'Mickey' Lauer <mickey@openmoko.org>
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Balaji Rao <balajirrao@openmoko.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The PCF50633 stores a month value of 1-12, but the kernel wants 0-11.
Signed-off-by: Rask Ingemann Lambertsen <rask@sygehus.dk>
Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Balaji Rao <balajirrao@openmoko.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
at91sam9g45 non ES lots have an alternate pixel clock calculation formula.
Introduce this one with condition on the cpu_is_xxxxx() macros.
Newer 9g45 SOC will not have good pixel clock calculation without this
fix.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Krzysztof Helt <krzysztof.h1@wp.pl>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix wrong bit mask for blanking register. Due to the error a CRT monitor
blanks off due to wrong frequency (out of range) instead of PM signal
(vertical and horizontal frequencies cut off).
Just compare the mask with bits set in the switch(blank) clause below the
changed line.
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Remove fb_save_state() and fb_restore_state operations from frame buffer layer.
They are used only in two drivers:
1. savagefb - and cause bug #11248
2. uvesafb
Usage of these operations is misunderstood in both drivers so kill these
operations, fix the bug #11248 and avoid confusion in the future.
Tested on Savage 3D/MV card and the patch fixes the bug #11248.
The frame buffer layer uses these funtions during switch between graphics
and text mode of the console, but these drivers saves state before
switching of the frame buffer (in the fb_open) and after releasing it (in
the fb_release). This defeats the purpose of these operations.
Addresses http://bugzilla.kernel.org/show_bug.cgi?id=11248
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Reported-by: Jochen Hein <jochen@jochen.org>
Tested-by: Jochen Hein <jochen@jochen.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michal Januszewski <spock@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Rafael debugged a resume-time hang (with oopses in workqueue handling)
on his laptop that was due to the 'waker' workqueue entry being
disconnected and then released without the workqueue entry having been
synchronized.
Several people were involved, with Oleg Nesterov doing a debugging patch
showing what workqueue entry was corrupt etc.
This was a regression introduced by commit 7bee549e19 ("Bluetooth: Add
USB autosuspend support to btusb driver") as Rafael points out (not
actually bisected, but it became clear once the bug was found).
Tested-and-reported-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Oliver Neukum <oliver@neukum.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6:
x86/PCI: Adjust GFP mask handling for coherent allocations
PCI ASPM: fix oops on root port removal
* 'drm-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6: (52 commits)
drm/kms: Init the CRTC info fields for modes forced from the command line.
drm/radeon/r600: CS parser updates
drm/radeon/kms: add debugfs for power management for AtomBIOS devices
drm/radeon/kms: initial mode validation support
drm/radeon/kms/atom/dce3: call transmitter init on mode set
drm/radeon/kms: store detailed connector info
drm/radeon/kms/atom/dce3: fix up usPixelClock calculation for Transmitter tables
drm/radeon/kms/r600: fix rs880 support v2
drm/radeon/kms/r700: fix some typos in chip init
drm/radeon/kms: remove some misleading debugging output
drm/radeon/kms: stop putting VRAM at 0 in MC space on r600s.
drm/radeon/kms: disable D1VGA and D2VGA if enabled
drm/radeon/kms: Don't RMW CP_RB_CNTL
drm/radeon/kms: fix coherency issues on AGP cards.
drm/radeon/kms: fix rc410 suspend/resume.
drm/radeon/kms: add quirk for hp dc5750
drm/radeon/kms/atom: fix potential oops in spread spectrum code
drm/kms: typo fix
drm/radeon/kms/atom: Make card_info per device
drm/radeon/kms/atom: Fix DVO support
...
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6: (27 commits)
V4L/DVB (13314): saa7134: set ts_force_val for the Hauppauge WinTV HVR-1150
V4L/DVB (13313): saa7134: add support for FORCE_TS_VALID mode for mpeg ts input
V4L/DVB (13311): uvcvideo: Fix compilation warning with 2.6.32 due to type mismatch with abs()
V4L/DVB (13309): uvcvideo: Ignore the FIX_BANDWIDTH for compressed video
V4L/DVB (13287): ce6230 - saa7164-cmd: Fix wrong sizeof
V4L/DVB (13286): pxa-camera: Fix missing sched.h
V4L/DVB (13264): gspca_mr97310a: Change vstart for CIF sensor type 1 cams
V4L/DVB (13257): gspca - m5602-s5k4aa: Add vflip for Fujitsu Amilo Xi 2528
V4L/DVB (13256): gspca - m5602-s5k4aa: Add another MSI GX700 vflip quirk
V4L/DVB (13255): gspca - m5602-s5k4aa: Add vflip quirk for the Bruneinit laptop
V4L/DVB (13240): firedtv: fix regression: tuning fails due to bogus error return
V4L/DVB (13237): firedtv: length field corrupt in ca2host if length>127
V4L/DVB (13230): s2255drv: Don't conditionalize video buffer completion on waiting processes
V4L/DVB (13202): smsusb: add autodetection support for three additional Hauppauge USB IDs
V4L/DVB (13190): em28xx: fix panic that can occur when starting audio streaming
V4L/DVB (13170): bttv: Fix reversed polarity error when switching video standard
V4L/DVB (13169): bttv: Fix potential out-of-order field processing
V4L/DVB (13167): pt1: Fix a compile error on arm
V4L/DVB (13132): fix use-after-free Oops, resulting from a driver-core API change
V4L/DVB (13131): pxa_camera: fix camera pixel format configuration
...
The commit d79c326 ("gpio-addr-flash: new driver for GPIO assisted
flash addressing") removed two lines from the Makefile by accident.
Though I'm not sure how this accident happened, this patch reverts the
removal.
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'i2c-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging:
i2c: Add an interface to lock/unlock an I2C bus segment
i2c-piix4: Modify code name SB900 to Hudson-2
* 'for-linus' of git://neil.brown.name/md:
md/raid5: make sure curr_sync_completes is uptodate when reshape starts
md: don't clear endpoint for resync when resync is interrupted.
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6: (34 commits)
net/fsl_pq_mdio: add module license GPL
can: fix WARN_ON dump in net/core/rtnetlink.c:rtmsg_ifinfo()
can: should not use __dev_get_by_index() without locks
hisax: remove bad udelay call to fix build error on ARM
ipip: Fix handling of DF packets when pmtudisc is OFF
qlge: Set PCIe reset type for EEH to fundamental.
qlge: Fix early exit from mbox cmd complete wait.
ixgbe: fix traffic hangs on Tx with ioatdma loaded
ixgbe: Fix checking TFCS register for TXOFF status when DCB is enabled
ixgbe: Fix gso_max_size for 82599 when DCB is enabled
macsonic: fix crash on PowerBook 520
NET: cassini, fix lock imbalance
ems_usb: Fix byte order issues on big endian machines
be2net: Bug fix to send config commands to hardware after netdev_register
be2net: fix to set proper flow control on resume
netfilter: xt_connlimit: fix regression caused by zero family value
rt2x00: Don't queue ieee80211 work after USB removal
Revert "ipw2200: fix oops on missing firmware"
decnet: netdevice refcount leak
netfilter: nf_nat: fix NAT issue in 2.6.30.4+
...
* 'sh/for-2.6.32' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6:
sh: Replace old style lock initializer
sh: Account for cache aliases in flush_icache_range()
sh: unwinder: Fix up invalid PC refetch in dwarf unwinder.
serial: sh-sci: disable callback typo fix
* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6:
ACPI: sleep: another HP/Compaq DMI entries for init_set_sci_en_on_resume
ACPI: add DMI entry for SCI_EN resume quirk on HP dv4
thermal: sysfs-api.txt - document passive attribute for thermal zones
thermal: sysfs-api.txt - reformat for improved readability
acpi: thermal: Add EOL to the trip_point_N_type strings
ACPI: Move dereference after NULL test
ACPICA: avoid "Info: mapping multiple BARs. Your kernel is fine."
ACPI: add __cpuinit to acpi_processor_add()
acpi-power-meter: Don't leak ACPI error codes to userspace
eeepc-laptop: don't enable camera at startup if it's already on.
Revert "eeepc-laptop: Prevent a panic when disabling RT2860 wireless when associated"
ACPI: clean up video.c boundary checks and types
or it will taint the kernel and fail to load becuase
of_address_to_resource() is GPL only.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
On older kernels, e.g. 2.6.27, a WARN_ON dump in rtmsg_ifinfo()
is thrown when the CAN device is registered due to insufficient
skb space, as reported by various users. This patch adds the
rtnl_link_ops "get_size" to fix the problem. I think this patch
is required for more recent kernels as well, even if no WARN_ON
dumps are triggered. Maybe we also need "get_xstats_size" for
the CAN xstats.
Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The Hauppauge WinTV HVR-1150 retail boards require the FORCE_TS_VALID bit
to be set in order to function properly. This change will work on the early
revisions on the board as well, but the final revision will not function
without this change.
Signed-off-by: Michael Krufky <mkrufky@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
When FORCE_TS_VALID mode is enabled, the saa713x will accept MPEG TS input
without requiring TS_VALID set high. This is required for some new boards
to function properly, due to the hardware design implementation.
The configuration is toggled within the board setup configuration. Boards
that do not have this bit set will function as before with no change.
Signed-off-by: Michael Krufky <mkrufky@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
The abs() macro has changed in 2.6.32 and returns a long instead of an
int. Fix the driver to avoid compilation warnings.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
The FIX_BANDWIDTH quirk tries to work around cameras requesting the
maximum bandwidth regardless of the image size by computing a bandwidth
estimate. This works only for uncompressed frames.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Which is why I have always preferred sizeof(struct foo) over
sizeof(var).
Cc: Antti Palosaari <crope@iki.fi>
Acked-by: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
gspca_mr97310a: Change vstart for CIF sensor type 1 cams
This fixes the distortion at the end of the frame, and avoids the bad frame
dropping done because of this distortion, trippling the framerate!
Signed-off-by: Theodore Kilgore <kilgota@banach.math.auburn.edu>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Adds a vflip quirk for the Fujitsu Amilo Xi 2528. Thanks to Evgeny for the report.
Signed-off-by: Erik Andrén <erik.andren@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Adds another vflip quirk for the MSI GX700.
Thanks to John Katzmaier for reporting.
Signed-off-by: Erik Andrén <erik.andren@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Adds a vflip quirk for the Bruneinit laptop. Thanks to Jörg for the report
Signed-off-by: Erik Andrén <erik.andren@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Since 2.6.32(-rc1), DVB core checks the return value of
dvb_frontend_ops.set_frontend. Now it becomes apparent that firedtv
always returned a bogus value from its set_frontend method.
CC: stable@kernel.org
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This solves a problem in firedtv that has become major for Swedish DVB-T
users the last month or so. It will most likely solve issues seen by
other users as well.
If the length of an AVC message is greater than 127, the length field
should be encoded in LV mode instead of V mode. V mode can only be used
if the length is 127 or less. This patch ensures that the CA_PMT
message is always encoded in LV mode so PMT message of greater lengths
can be supported.
Signed-off-by: Henrik Kurelid <henrik@kurelid.se>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
The s2255 driver had logic which aborted processing of a video frame
if there was no process waiting on the video buffer in question. That
simply doesn't work when the application is doing things in an
asynchronous manner. If the application went to the trouble to queue
the buffer in the first place, then the driver should always attempt
to complete it - even if the application at that moment has its
attention turned elsewhere. Applications which always blocked waiting
for I/O on the capture device would not have been affected by this.
Applications which *mostly* blocked waiting for I/O on the capture
device probably only would have been somewhat affected (frame lossage,
at a rate which goes up as the application blocks less). Applications
which never blocked on the capture device (e.g. polling only) however
would never have been able to receive any video frames, since in that
case this "is anyone waiting on this?" check on the buffer never would
have evalutated true. This patch just deletes that harmful check
against the buffer's wait queue.
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
CC: stable@kernel.org
Add support for three new Hauppauge Device USB IDs:
2040:b900
2040:b910
2040:c000
Signed-off-by: Michael Krufky <mkrufky@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Because the counters were not reset when starting up streaming, they would
be reused from the previous run. This can result in cases such that when the
second instance of streaming starts up, the "cnt" variable in
em28xx_audio_isocirq() can end up being negative, resulting in attempting to
write to memory before the start of runtime->dma_area (as well as having a
negative number of bytes to copy).
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
CC: stable@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
The bttv driver function which handles switching of the video standard
(set_tvnorm() in bttv-driver.c) includes a check which can optionally
also reset the cropping configuration to a default value. It is
"optional" based on a comparison of the cropcap parameters of the
previous vs the newly requested video standard. The comparison is
being done with a memcmp(), a function which only returns a true value
if the comparison actually fails.
This if-statement appears to have been written to assume wrong
memcmp() semantics. That is, it was re-initializing the cropping
configuration only if the new video standard did NOT have different
cropcap values. That doesn't make any sense. One definitely should
reset things if the cropcap parameters are different - if there's any
comparison to made at all.
The effect of this problem was that a transition from, say, PAL to
NTSC would leave in place old cropping setup that made sense for the
PAL geometry but not for NTSC. If the application doesn't care about
cropping it also won't try to reset the cropping configuration,
resulting in an improperly cropped video frame. In the case I was
testing this actually caused black video frames to be displayed.
Another interesting effect of this bug is that if one does something
which does NOT change the video standard and this function is run,
then the cropping setup gets reset anyway - again because of the
backwards comparison. It turns out that just running anything which
merely opens and closes the video device node (e.g. v4l-info) will
cause this to happen. One can argue that simply opening the device
node and not doing anything to it should not mess with any of its
state - but because of this behavior, any TV app which does such
things (e.g. xawtv) probably therefore doesn't see the problem.
The solution is to fix the sense of the if-statement. It's easy to
see how this mistake could have been made given how memcmp() works.
The patch is therefore removal of a single "!" character from the
if-statement in set_tvnorm in bttv-driver.c.
Signed-off-by: Mike Isely <isely@pobox.com>
CC: stable@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
There is a subtle interaction in the bttv driver which can result in
fields being repeatedly processed out of order. This is a problem
specifically when running in V4L2_FIELD_ALTERNATE mode (probably the
most common case).
1. The determination of which fields are associated with which buffers
happens in videobuf, before the bttv driver gets a chance to queue the
corresponding DMA. Thus by the point when the DMA is queued for a
given buffer, the algorithm has to do the queuing based on the
buffer's already assigned field type - not based on which field is
"next" in the video stream.
2. The driver normally tries to queue both the top and bottom fields
at the same time (see bttv_irq_next_video()). It tries to sort out
top vs bottom by looking at the field type for the next 2 available
buffers and assigning them appropriately.
3. However the bttv driver *always* actually processes the top field
first. There's even an interrupt set aside for specifically
recognizing when the top field has been processed so that it can be
marked done even while the bottom field is still being DMAed.
Given all of the above, if one gets into a situation where
bttv_irq_next_video() gets entered when the first available buffer has
been pre-associated as a bottom field, then the function is going to
process the buffers out of order. That first available buffer will be
put into the bottom field slot and the buffer after that will be put
into the top field slot. Problem is, since the top field is always
processed first by the driver, then that second buffer (the one after
the first available buffer) will be the first one to be finished.
Because of the strict fifo handling of all video buffers, then that
top field won't be seen by the app until after the bottom field is
also processed. Worse still, the app will get back the
chronologically later bottom field first, *before* the top field is
received. The buffer's timestamps will even be backwards.
While not fatal to most TV apps, this behavior can subtlely degrade
userspace deinterlacing (probably will cause jitter). That's probably
why it has gone unnoticed. But it will also cause serious problems if
the app in question discards all but the latest received buffer (a
latency minimizing tactic) - causing one field to only ever be
displayed since the other is now always late. Unfortunately once you
get into this state, you're stuck this way - because having consumed
two buffers, now the next time around the "first" available buffer
will again be a bottom field and the same thing happens.
How can we get into this state? In a perfect world, where there's
always a few free buffers queued to the driver, it should be
impossible. However if something disrupts streaming, e.g. if the
userspace app can't queue free buffers fast enough for a moment due
perhaps to a CPU scheduling glitch, then the driver can get
momentarily starved and some number of fields will be dropped. That's
OK. But if an odd number of fields get dropped, then that "first"
available buffer might be the bottom field and now we're stuck...
This patch fixes that problem by deliberately only setting up a single
field for one frame if we don't get a top field as the first available
buffer. By purposely skipping the other field, then we only handle a
single buffer thus bringing things back into proper sync (i.e. top
field first) for the next frame. To do this we just drop the few
lines in bttv_irq_next_video() that attempt to set up the second
buffer when that second buffer isn't for the bottom field.
This is definitely a problem in when in V4L2_FIELD_ALTERNATE mode. In
the other modes this change either has no effect or doesn't harm
things any further anyway.
Signed-off-by: Mike Isely <isely@pobox.com>
CC: stable@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Ingo Molnar