Hans Verkuil b3379c6201 [media] vb2: only call start_streaming if sufficient buffers are queued ... In commit 02f142ecd2 support was added to start_streaming to return -ENOBUFS if insufficient buffers were queued for the DMA engine to start. The vb2 core would attempt calling start_streaming again if another buffer would be queued up. Later analysis uncovered problems with the queue management if start_streaming would return an error: the buffers are enqueued to the driver before the start_streaming op is called, so after an error they are never returned to the vb2 core. The solution for this is to let the driver return them to the vb2 core in case of an error while starting the DMA engine. However, in the case of -ENOBUFS that would be weird: it is not a real error, it just says that more buffers are needed. Requiring start_streaming to give them back only to have them requeued again the next time the application calls QBUF is inefficient. This patch changes this mechanism: it adds a 'min_buffers_needed' field to vb2_queue that drivers can set with the minimum number of buffers required to start the DMA engine. The start_streaming op is only called if enough buffers are queued. The -ENOBUFS handling has been dropped in favor of this new method. Drivers are expected to return buffers back to vb2 core with state QUEUED if start_streaming would return an error. The vb2 core checks for this and produces a warning if that didn't happen and it will forcefully reclaim such buffers to ensure that the internal vb2 core state remains consistent and all buffer-related resources have been correctly freed and all op calls have been balanced. __reqbufs() has been updated to check that at least min_buffers_needed buffers could be allocated. If fewer buffers were allocated then __reqbufs will free what was allocated and return -ENOMEM. Based on a suggestion from Pawel Osciak. __create_bufs() doesn't do that check, since the use of __create_bufs assumes some advance scenario where the user might want more control. Instead streamon will check if enough buffers were allocated to prevent streaming with fewer than the minimum required number of buffers. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>		2014-03-11 06:56:41 -03:00
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acpi	Merge branches 'acpi-processor', 'acpi-hotplug', 'acpi-init', 'acpi-pm' and 'acpica'	2014-01-29 11:47:18 +01:00
asm-generic	mm: Use ptep/pmdp_set_numa() for updating _PAGE_NUMA bit	2014-02-17 11:19:36 +11:00
clocksource	…
crypto	…
drm	Merge tag 'ttm-fixes-3.14-2014-02-18' of git://people.freedesktop.org/~thomash/linux into drm-fixes	2014-02-19 08:21:26 +10:00
dt-bindings	Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc	2014-01-30 17:07:18 -08:00
keys	…
kvm	KVM: arm-vgic: Set base addr through device API	2013-12-21 10:01:22 -08:00
linux	Driver core fix for 3.14-rc5	2014-03-02 15:13:41 -08:00
math-emu	math-emu: fix floating-point to integer overflow detection	2014-01-07 18:36:24 -06:00
media	[media] vb2: only call start_streaming if sufficient buffers are queued	2014-03-11 06:56:41 -03:00
memory	…
misc	…
net	net: sctp: Fix a_rwnd/rwnd management to reflect real state of the receiver's buffer	2014-02-17 00:16:56 -05:00
pcmcia	…
ras	…
rdma	IB: Report using RoCE IP based gids in port caps	2014-02-13 14:46:03 -08:00
rxrpc	…
scsi	Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending	2014-01-31 15:31:23 -08:00
sound	ASoC: dapm: Add locking to snd_soc_dapm_xxxx_pin functions	2014-02-20 18:40:07 +09:00
target	target: Simplify command completion by removing CMD_T_FAILED flag	2014-02-12 15:14:30 -08:00
trace	Linux 3.14-rc5	2014-03-11 06:55:49 -03:00
uapi	Linux 3.14-rc5	2014-03-11 06:55:49 -03:00
video	video: pxa168fb: Cleanup pxa168fb.h file	2014-01-17 10:57:43 +02:00
xen	Merge branch 'for-linus' of git://git.kernel.dk/linux-block	2014-02-14 10:45:18 -08:00
Kbuild	…