leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
4c78513e45
linux/Documentation
History
Daniel Vetter 4c78513e45 dma-buf: mmap support 
Compared to Rob Clark's RFC I've ditched the prepare/finish hooks
and corresponding ioctls on the dma_buf file. The major reason for
that is that many people seem to be under the impression that this is
also for synchronization with outstanding asynchronous processsing.
I'm pretty massively opposed to this because:

- It boils down reinventing a new rather general-purpose userspace
  synchronization interface. If we look at things like futexes, this
  is hard to get right.
- Furthermore a lot of kernel code has to interact with this
  synchronization primitive. This smells a look like the dri1 hw_lock,
  a horror show I prefer not to reinvent.
- Even more fun is that multiple different subsystems would interact
  here, so we have plenty of opportunities to create funny deadlock
  scenarios.

I think synchronization is a wholesale different problem from data
sharing and should be tackled as an orthogonal problem.

Now we could demand that prepare/finish may only ensure cache
coherency (as Rob intended), but that runs up into the next problem:
We not only need mmap support to facilitate sw-only processing nodes
in a pipeline (without jumping through hoops by importing the dma_buf
into some sw-access only importer), which allows for a nicer
ION->dma-buf upgrade path for existing Android userspace. We also need
mmap support for existing importing subsystems to support existing
userspace libraries. And a loot of these subsystems are expected to
export coherent userspace mappings.

So prepare/finish can only ever be optional and the exporter /needs/
to support coherent mappings. Given that mmap access is always
somewhat fallback-y in nature I've decided to drop this optimization,
instead of just making it optional. If we demonstrate a clear need for
this, supported by benchmark results, we can always add it in again
later as an optional extension.

Other differences compared to Rob's RFC is the above mentioned support
for mapping a dma-buf through facilities provided by the importer.
Which results in mmap support no longer being optional.

Note that this dma-buf mmap patch does _not_ support every possible
insanity an existing subsystem could pull of with mmap: Because it
does not allow to intercept pagefaults and shoot down ptes importing
subsystems can't add some magic of their own at these points (e.g. to
automatically synchronize with outstanding rendering or set up some
special resources). I've done a cursory read through a few mmap
implementions of various subsytems and I'm hopeful that we can avoid
this (and the complexity it'd bring with it).

Additonally I've extended the documentation a bit to explain the hows
and whys of this mmap extension.

In case we ever want to add support for explicitly cache maneged
userspace mmap with a prepare/finish ioctl pair, we could specify that
userspace needs to mmap a different part of the dma_buf, e.g. the
range starting at dma_buf->size up to dma_buf->size*2. This works
because the size of a dma_buf is invariant over it's lifetime. The
exporter would obviously need to fall back to coherent mappings for
both ranges if a legacy clients maps the coherent range and the
architecture cannot suppor conflicting caching policies. Also, this
would obviously be optional and userspace needs to be able to fall
back to coherent mappings.

v2:
- Spelling fixes from Rob Clark.
- Compile fix for !DMA_BUF from Rob Clark.
- Extend commit message to explain how explicitly cache managed mmap
  support could be added later.
- Extend the documentation with implementations notes for exporters
  that need to manually fake coherency.

v3:
- dma_buf pointer initialization goof-up noticed by Rebecca Schultz
  Zavin.

Cc: Rob Clark <rob.clark@linaro.org>
Cc: Rebecca Schultz Zavin <rebecca@android.com>
Acked-by: Rob Clark <rob.clark@linaro.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
2012-05-25 12:35:24 +05:30
..
ABI HSI: Add HSI ABI documentation 2012-04-23 14:23:32 +03:00
accounting Documentation: update cgroupfs mount point 2011-06-15 21:52:50 -07:00
acpi Update documentation for parameter *notrigger* in einj.txt 2012-03-30 03:30:19 -04:00
aoe Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
arm Documentation: Fix multiple typo in Documentation 2012-03-07 16:08:24 +01:00
auxdisplay
backlight backlight: new backlight driver for LP855x devices 2012-03-23 16:58:33 -07:00
blackfin doc: fix broken references 2011-09-27 18:08:04 +02:00
block Documentation: drop as block elevator reference in switching-sched.txt 2011-11-04 12:01:48 -07:00
blockdev Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
cdrom doc: fix broken references 2011-09-27 18:08:04 +02:00
cgroups memcg: fix up documentation on global LRU 2012-04-12 13:12:11 -07:00
connector Documentation/: it's -> its where appropriate 2010-04-23 02:09:52 +02:00
console
cpu-freq Doc: cpufreq: Fix typo and outdated line 2011-11-08 10:23:29 +01:00
cpuidle cpuidle: add a sysfs entry to disable specific C state for debug purpose. 2012-03-30 01:52:58 -04:00
cris
crypto
development-process Documentation: Update stable address 2011-12-12 14:14:31 -08:00
device-mapper dm: add verity target 2012-03-28 18:43:38 +01:00
devicetree sound fixes for 3.4-rc6 2012-05-05 10:07:06 -07:00
DocBook Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media 2012-04-21 12:43:23 -07:00
driver-model Merge remote-tracking branches 'regulator/topic/devm' and 'regulator/topic/stub' into regulator-next 2012-03-18 21:38:28 +00:00
dvb [media] lmedm04 RS2000 Firmware details 2012-03-19 14:55:55 -03:00
early-userspace
EDID drm: allow loading an EDID as firmware to override broken monitor 2012-03-20 10:09:28 +00:00
fault-injection fault-injection: update documentation with the mmc module param 2011-10-26 16:32:13 -04:00
fb Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
filesystems typo fix in Documentation/filesystems/vfs.txt 2012-04-09 01:39:24 -04:00
firmware_class firmware: Update hotplug script 2010-08-05 13:53:34 -07:00
frv doc: fix broken references 2011-09-27 18:08:04 +02:00
hid HID: Move hiddev.txt to the new Documentation/hid directory 2011-03-22 11:43:51 +01:00
hwmon hwmon: (k10temp) Add support for AMD Trinity CPUs 2012-04-01 10:25:56 -07:00
i2c Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
i2o Documentation: Fix multiple typo in Documentation 2012-03-07 16:08:24 +01:00
ia64 Fix common misspellings 2011-03-31 11:26:23 -03:00
ide Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
infiniband Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
input Documentation: input.txt: clarify mousedev 'cat' command syntax 2012-03-30 16:03:15 -07:00
ioctl Merge branch 'for-next' of git://gitorious.org/kernel-hsi/kernel-hsi 2012-04-02 09:50:40 -07:00
isdn Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
ja_JP Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core-2.6 2011-07-25 23:06:24 -07:00
kbuild Documentation: mention scripts/diffconfig tool 2012-03-30 16:03:15 -07:00
kdump [S390] Add s390x description to Documentation/kdump/kdump.txt 2011-12-27 11:27:13 +01:00
ko_KR driver-core: documentation: fix up Greg's email address 2012-02-15 14:48:01 -08:00
laptops Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
leds drivers/leds/leds-lp5521.c: support led pattern data 2012-03-23 16:58:34 -07:00
m68k Documentation: add pointer to name_to_dev_t for root= values 2011-08-03 14:25:21 -10:00
make kbuild: introduce HDR_ARCH_LIST for headers_install_all 2010-12-14 22:16:19 +01:00
mips Fix common misspellings 2011-03-31 11:26:23 -03:00
misc-devices Fix common misspellings 2011-03-31 11:26:23 -03:00
mmc mmc: core: Fixup delayed work clock gating patch 2012-01-11 23:58:43 -05:00
mn10300
mtd Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
namespaces
netlabel Documentation/: it's -> its where appropriate 2010-04-23 02:09:52 +02:00
networking tcp: change tcp_adv_win_scale and tcp_rmem[2] 2012-05-02 21:08:58 -04:00
nfc NFC: Driver for NXP Semiconductors PN544 NFC chip. 2011-01-13 08:03:19 -08:00
parisc
PCI doc: fix broken references 2011-09-27 18:08:04 +02:00
pcmcia pcmcia: use autoconfiguration feature for ioports and iomem 2010-09-29 17:20:24 +02:00
power PM / Freezer / Docs: Update documentation about freezing of tasks 2012-04-29 22:29:30 +02:00
powerpc Documentation/powerpc/mpc52xx.txt: Checkpatch cleanup 2012-03-18 23:59:34 +01:00
pps pps: add parallel port PPS signal generator 2011-01-13 08:03:21 -08:00
prctl
pti Kernel documentation for the PTI feature. 2011-05-13 16:31:00 -07:00
ptp ptp: Added a brand new class driver for ptp clocks. 2011-05-23 13:01:00 -07:00
rapidio RapidIO: documentation update 2011-11-02 16:07:02 -07:00
RCU rcu: Call out dangers of expedited RCU primitives 2012-02-21 09:06:08 -08:00
s390 Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
scheduler sched: Remove sched_switch 2012-01-27 13:28:53 +01:00
scsi SCSI updates on 20120331 2012-03-31 13:31:23 -07:00
security keys: update the documentation with info about "logon" keys 2012-04-25 12:46:50 -04:00
serial Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
sh sh: clkfwk: Kill off unused clk_set_rate_ex(). 2010-11-15 18:25:12 +09:00
sound ALSA: hda/realtek - Add a few ALC882 model strings back 2012-04-11 14:10:57 +02:00
sparc
spi spi: create a message queueing infrastructure 2012-03-07 19:19:48 -07:00
sysctl Documentation: add missing tainted bits to Documentation/sysctl/kernel.txt 2012-02-06 16:29:19 -08:00
target Documentation: Fix typo in tcm_mod_builder.py 2012-02-10 09:52:18 +01:00
telephony Fix common misspellings 2011-03-31 11:26:23 -03:00
thermal thermal: Rename generate_netlink_event 2012-01-23 03:15:25 -05:00
timers doc: fix broken references 2011-09-27 18:08:04 +02:00
trace Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-03-20 21:12:50 -07:00
usb USB documentation: explain lifetime rules for unlinking URBs 2012-04-06 13:54:00 -07:00
vDSO Document the vDSO and add a reference parser 2011-07-14 17:57:09 -07:00
video4linux Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
virtual Merge branch 'kvm-updates/3.4' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2012-03-28 14:35:31 -07:00
vm mm: move hugepage test examples to tools/testing/selftests/vm 2012-03-28 17:14:37 -07:00
w1 Fix common misspellings 2011-03-31 11:26:23 -03:00
watchdog watchdog: Add support for WDIOC_GETTIMELEFT IOCTL in watchdog core 2012-03-27 20:15:37 +02:00
wimax
x86 x86-64, doc: Remove int 0xcc from entry_64.S documentation 2011-08-16 08:04:08 -07:00
zh_CN Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2012-03-20 21:04:47 -07:00
.gitignore add random binaries to .gitignore 2010-04-08 11:34:34 +02:00
00-INDEX crc32: move long comment about crc32 fundamentals to Documentation/ 2012-03-23 16:58:37 -07:00
applying-patches.txt
atomic_ops.txt doc: Add load/store guarantees to Documentation/atomic-ops.txt 2011-12-11 10:31:58 -08:00
bad_memory.txt
basic_profiling.txt
binfmt_misc.txt Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
braille-console.txt
bt8xxgpio.txt
btmrvl.txt
BUG-HUNTING
bus-virt-phys-mapping.txt doc: fix broken references 2011-09-27 18:08:04 +02:00
cachetlb.txt mm: convert mm->cpu_vm_cpumask into cpumask_var_t 2011-05-25 08:39:21 -07:00
Changes Documentation/Changes: remove some really obsolete text 2011-07-11 16:48:38 -07:00
circular-buffers.txt Document Linux's circular buffering capabilities 2010-03-24 16:31:22 -07:00
clk.txt Documentation: common clk API 2012-03-16 20:35:01 +00:00
coccinelle.txt coccinelle.txt: update documentation to include M= option 2012-01-14 22:25:56 +01:00
CodingStyle Documentation: CodingStyle: add inline assembly guidelines 2012-03-30 16:03:15 -07:00
cpu-hotplug.txt documentation: remove references to cpu_*_map. 2012-03-29 15:38:31 +10:30
cpu-load.txt
cputopology.txt topology/sysfs: Provide book id and siblings attributes 2010-09-09 20:41:25 +02:00
crc32.txt crc32: move long comment about crc32 fundamentals to Documentation/ 2012-03-23 16:58:37 -07:00
dcdbas.txt
debugging-modules.txt
debugging-via-ohci1394.txt
dell_rbu.txt Fix common misspellings 2011-03-31 11:26:23 -03:00
devices.txt vhost-net: add module alias (v2.1) 2012-01-13 10:12:23 -08:00
digsig.txt crypto: digital signature verification support 2011-11-09 12:10:37 +02:00
DMA-API-HOWTO.txt Documentation/DMA-API-HOWTO.txt: fix misleading example 2011-07-26 16:49:45 -07:00
DMA-API.txt include/linux/dma-mapping.h: add dma_zalloc_coherent() 2011-11-02 16:07:02 -07:00
DMA-attributes.txt common: DMA-mapping: add NON-CONSISTENT attribute 2012-03-28 16:36:44 +02:00
dma-buf-sharing.txt dma-buf: mmap support 2012-05-25 12:35:24 +05:30
DMA-ISA-LPC.txt
dmaengine.txt Documentation: Fix multiple typo in Documentation 2012-03-07 16:08:24 +01:00
dontdiff Documentation: remove 'mach' from dontdiff file 2012-03-30 16:03:15 -07:00
dynamic-debug-howto.txt dynamic_debug: process multiple debug-queries on a line 2012-01-24 12:50:36 -08:00
edac.txt EDAC: Correct scrub rate API 2012-03-19 12:03:58 +01:00
eisa.txt Fix common misspellings 2011-03-31 11:26:23 -03:00
email-clients.txt Documentation: email-clients: Add better Thunderbird information 2011-08-13 18:34:03 -07:00
feature-removal-schedule.txt Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media 2012-05-14 11:23:37 -07:00
flexible-arrays.txt flex_array: flex_array_prealloc takes a number of elements, not an end 2011-04-28 16:12:47 -04:00
futex-requeue-pi.txt
gcov.txt
gpio.txt Documentation/gpio.txt: Explain expected pinctrl interaction 2012-03-12 11:27:07 -06:00
highuid.txt
HOWTO Documentation: Update stable address 2011-12-12 14:14:31 -08:00
hw_random.txt
hwspinlock.txt hwspinlock/core: register a bank of hwspinlocks in a single API call 2011-09-21 19:45:34 +03:00
init.txt
initrd.txt
intel_txt.txt Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
Intel-IOMMU.txt
io_ordering.txt
io-mapping.txt
iostats.txt Documentation/iostats.txt: bit-size reference etc. 2011-03-23 20:44:18 +01:00
IPMI.txt IPMI: Add the document description of ipmi_get_smi_info 2010-12-14 00:22:00 -05:00
IRQ-affinity.txt bitmap, irq: add smp_affinity_list interface to /proc/irq 2011-05-25 08:39:45 -07:00
IRQ-domain.txt irq_domain: add documentation and MAINTAINERS entry. 2012-02-14 14:06:47 -07:00
IRQ.txt
irqflags-tracing.txt Fix common misspellings 2011-03-31 11:26:23 -03:00
isapnp.txt
java.txt
kernel-doc-nano-HOWTO.txt docbook: warn on unused doc entries 2010-09-11 16:49:21 -07:00
kernel-docs.txt doc: fix broken references 2011-09-27 18:08:04 +02:00
kernel-parameters.txt Merge branch 'for-3.4' of git://linux-nfs.org/~bfields/linux 2012-03-29 14:53:25 -07:00
kmemcheck.txt
kmemleak.txt kmemleak: Handle percpu memory allocation 2011-12-02 16:12:42 +00:00
kobject.txt driver-core: documentation: fix up Greg's email address 2012-02-15 14:48:01 -08:00
kprobes.txt tree-wide: fix comment/printk typos 2010-11-01 15:38:34 -04:00
kref.txt kref: Fix typo in kref documentation 2011-03-07 13:20:05 -08:00
ldm.txt Documentation: update broken web addresses. 2010-08-04 15:21:40 +02:00
local_ops.txt
lockdep-design.txt lockdep: Update documentation for lock-class leak detection 2011-12-11 10:31:23 -08:00
lockstat.txt Documentation: Add statistics about nested locks 2011-05-28 17:03:29 +02:00
lockup-watchdogs.txt watchdog: Update documentation 2012-02-11 15:11:28 +01:00
logo.gif
logo.txt
magic-number.txt drivers/net: fix up stale paths from driver reorg 2012-01-30 12:54:40 -05:00
Makefile mm: move hugepage test examples to tools/testing/selftests/vm 2012-03-28 17:14:37 -07:00
ManagementStyle
mca.txt doc: fix wrong arch/i386 references 2011-06-13 13:43:05 +02:00
md.txt md: create externally visible flags for supporting hot-replace. 2011-12-23 10:17:51 +11:00
media-framework.txt doc: fix broken references 2011-09-27 18:08:04 +02:00
memory-barriers.txt doc: fix broken references 2011-09-27 18:08:04 +02:00
memory-hotplug.txt memory hotplug: Allow memory blocks to span multiple memory sections 2011-02-03 16:08:57 -08:00
memory.txt
mono.txt Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
mutex-design.txt mutex: Fix annotations to include it in kernel-locking docbook 2010-09-03 08:19:51 +02:00
nommu-mmap.txt
numastat.txt Doc: Update numastat.txt 2012-02-28 16:05:06 +01:00
oops-tracing.txt module,bug: Add TAINT_OOT_MODULE flag for modules not built in-tree 2011-11-07 07:54:42 +10:30
padata.txt Documentation/padata.txt: fix typos etc. 2010-08-11 08:59:18 -07:00
parport-lowlevel.txt
parport.txt Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
pi-futex.txt
pinctrl.txt pinctrl: enhance mapping table to support pin config operations 2012-03-05 11:25:11 +01:00
pnp.txt
preempt-locking.txt
printk-formats.txt Documentation: update printk-formats.txt 2011-06-15 21:52:50 -07:00
prio_tree.txt
ramoops.txt Documentation: add Ramoops usage description 2011-08-13 18:34:03 -07:00
rbtree.txt Documentation: Update augmented rbtree documentation 2011-07-24 10:03:05 -07:00
remoteproc.txt remoteproc: remove the single rpmsg vdev limitation 2012-03-06 19:14:12 +02:00
rfkill.txt doc: fix broken references 2011-09-27 18:08:04 +02:00
robust-futex-ABI.txt
robust-futexes.txt
rpmsg.txt rpmsg: add virtio-based remote processor messaging bus 2012-02-08 22:53:58 +02:00
rt-mutex-design.txt variable name fix to Documentation/rt-mutex-design.txt 2010-06-05 17:39:09 +02:00
rt-mutex.txt
rtc.txt RTC: Fix up rtc.txt documentation to reflect changes to generic rtc layer 2011-03-09 11:25:10 -08:00
SAK.txt
SecurityBugs Fix common misspellings 2011-03-31 11:26:23 -03:00
serial-console.txt
sgi-ioc4.txt
sgi-visws.txt
SM501.txt
sparse.txt update email address 2010-07-19 10:56:54 +02:00
spinlocks.txt Documentation/spinlocks.txt: Remove reference to sti()/cli() 2011-07-11 12:45:04 -07:00
stable_api_nonsense.txt doc: stable_api_nonsense.txt: fix paragraph to make more sense. 2011-03-30 12:02:05 +02:00
stable_kernel_rules.txt stable: update documentation to ask for kernel version 2012-01-24 10:50:22 -08:00
static-keys.txt static keys: Add docs better explaining the whole 'struct static_key' mechanism 2012-02-24 09:12:19 +01:00
SubmitChecklist Documentation/SubmitChecklist: add RCU debug config options 2011-07-25 20:57:17 -07:00
SubmittingDrivers Documentation: SubmittingDrivers: fix Linus's git tree URL 2011-08-13 18:34:03 -07:00
SubmittingPatches Documentation: fix spelling error in SubmittingPatches 2011-08-13 18:34:02 -07:00
svga.txt
sysfs-rules.txt Fix typos in comments 2010-03-16 11:47:56 +01:00
sysrq.txt Documentation: sysrq: Crutcher Dunnavant is unavailable 2012-03-30 16:03:15 -07:00
unaligned-memory-access.txt
unicode.txt
unshare.txt
VGA-softcursor.txt
vgaarbiter.txt misc latin1 to utf8 conversions 2012-01-02 13:04:55 +01:00
video-output.txt
volatile-considered-harmful.txt Documentation/volatile-considered-harmful.txt: correct cpu_relax() documentation 2010-03-24 16:31:20 -07:00
workqueue.txt workqueue: Document debugging tricks 2011-03-31 13:40:42 +02:00
xz.txt decompressors: add XZ decompressor module 2011-01-13 08:03:24 -08:00
zorro.txt