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Subject[2.6.22.2 review 30/84] V4L: ivtv: Add locking to ensure stream setup is atomic

From: Hans Verkuil <hverkuil@xs4all.nl>

Starting an MPEG and VBI capture simultaneously caused errors in
the VBI setup: this setup was done twice when it should be done
only for the first stream that is opened.
Added a mutex to prevent this from happening.

(cherry picked from commit f885969196da6ae905162c0d1c5f0553de12cb40)

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>

---
drivers/media/video/ivtv/ivtv-driver.c | 1 +
drivers/media/video/ivtv/ivtv-driver.h | 1 +
drivers/media/video/ivtv/ivtv-streams.c | 30 +++++++++++++++++++-----------
3 files changed, 21 insertions(+), 11 deletions(-)
--- a/drivers/media/video/ivtv/ivtv-driver.c
+++ b/drivers/media/video/ivtv/ivtv-driver.c
@@ -622,6 +622,7 @@ static int __devinit ivtv_init_struct1(s
itv->enc_mbox.max_mbox = 2; /* the encoder has 3 mailboxes (0-2) */
itv->dec_mbox.max_mbox = 1; /* the decoder has 2 mailboxes (0-1) */

+ mutex_init(&itv->serialize_lock);
mutex_init(&itv->i2c_bus_lock);
mutex_init(&itv->udma.lock);

--- a/drivers/media/video/ivtv/ivtv-driver.h
+++ b/drivers/media/video/ivtv/ivtv-driver.h
@@ -722,6 +722,7 @@ struct ivtv {
int search_pack_header;

spinlock_t dma_reg_lock; /* lock access to DMA engine registers */
+ struct mutex serialize_lock; /* lock used to serialize starting streams */

/* User based DMA for OSD */
struct ivtv_user_dma udma;
--- a/drivers/media/video/ivtv/ivtv-streams.c
+++ b/drivers/media/video/ivtv/ivtv-streams.c
@@ -446,6 +446,9 @@ int ivtv_start_v4l2_encode_stream(struct
if (s->v4l2dev == NULL)
return -EINVAL;

+ /* Big serialization lock to ensure no two streams are started
+ simultaneously: that can give all sorts of weird results. */
+ mutex_lock(&itv->serialize_lock);
IVTV_DEBUG_INFO("Start encoder stream %s\n", s->name);

switch (s->type) {
@@ -487,6 +490,7 @@ int ivtv_start_v4l2_encode_stream(struct
0, sizeof(itv->vbi.sliced_mpeg_size));
break;
default:
+ mutex_unlock(&itv->serialize_lock);
return -EINVAL;
}
s->subtype = subtype;
@@ -568,6 +572,7 @@ int ivtv_start_v4l2_encode_stream(struct
if (ivtv_vapi(itv, CX2341X_ENC_START_CAPTURE, 2, captype, subtype))
{
IVTV_DEBUG_WARN( "Error starting capture!\n");
+ mutex_unlock(&itv->serialize_lock);
return -EINVAL;
}

@@ -583,6 +588,7 @@ int ivtv_start_v4l2_encode_stream(struct

/* you're live! sit back and await interrupts :) */
atomic_inc(&itv->capturing);
+ mutex_unlock(&itv->serialize_lock);
return 0;
}

@@ -762,17 +768,6 @@ int ivtv_stop_v4l2_encode_stream(struct
/* when: 0 = end of GOP 1 = NOW!, type: 0 = mpeg, subtype: 3 = video+audio */
ivtv_vapi(itv, CX2341X_ENC_STOP_CAPTURE, 3, stopmode, cap_type, s->subtype);

- /* only run these if we're shutting down the last cap */
- if (atomic_read(&itv->capturing) - 1 == 0) {
- /* event notification (off) */
- if (test_and_clear_bit(IVTV_F_I_DIG_RST, &itv->i_flags)) {
- /* type: 0 = refresh */
- /* on/off: 0 = off, intr: 0x10000000, mbox_id: -1: none */
- ivtv_vapi(itv, CX2341X_ENC_SET_EVENT_NOTIFICATION, 4, 0, 0, IVTV_IRQ_ENC_VIM_RST, -1);
- ivtv_set_irq_mask(itv, IVTV_IRQ_ENC_VIM_RST);
- }
- }
-
then = jiffies;

if (!test_bit(IVTV_F_S_PASSTHROUGH, &s->s_flags)) {
@@ -840,17 +835,30 @@ int ivtv_stop_v4l2_encode_stream(struct
/* Clear capture and no-read bits */
clear_bit(IVTV_F_S_STREAMING, &s->s_flags);

+ /* ensure these global cleanup actions are done only once */
+ mutex_lock(&itv->serialize_lock);
+
if (s->type == IVTV_ENC_STREAM_TYPE_VBI)
ivtv_set_irq_mask(itv, IVTV_IRQ_ENC_VBI_CAP);

if (atomic_read(&itv->capturing) > 0) {
+ mutex_unlock(&itv->serialize_lock);
return 0;
}

/* Set the following Interrupt mask bits for capture */
ivtv_set_irq_mask(itv, IVTV_IRQ_MASK_CAPTURE);

+ /* event notification (off) */
+ if (test_and_clear_bit(IVTV_F_I_DIG_RST, &itv->i_flags)) {
+ /* type: 0 = refresh */
+ /* on/off: 0 = off, intr: 0x10000000, mbox_id: -1: none */
+ ivtv_vapi(itv, CX2341X_ENC_SET_EVENT_NOTIFICATION, 4, 0, 0, IVTV_IRQ_ENC_VIM_RST, -1);
+ ivtv_set_irq_mask(itv, IVTV_IRQ_ENC_VIM_RST);
+ }
+
wake_up(&s->waitq);
+ mutex_unlock(&itv->serialize_lock);

return 0;
}
--
-
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