[RESEND PATCH] [media] s5p-mfc: don't close instance after free OUTPUT buffers

From: Javier Martinez Canillas
Date: Fri May 06 2016 - 18:11:49 EST

From: ayaka <ayaka@xxxxxxxxxxx>

User-space applications can use the VIDIOC_REQBUFS ioctl to determine if a
memory mapped, user pointer or DMABUF based I/O is supported by the driver.

So a set of VIDIOC_REQBUFS ioctl calls will be made with count 0 and then
the real VIDIOC_REQBUFS call with count == n. But for count 0, the driver
not only frees the buffer but also closes the MFC instance and s5p_mfc_ctx
state is set to MFCINST_FREE.

The VIDIOC_REQBUFS handler for the output device checks if the s5p_mfc_ctx
state is set to MFCINST_INIT (which happens on an VIDIOC_S_FMT) and fails
otherwise. So after a VIDIOC_REQBUFS(n), future VIDIOC_REQBUFS(n) calls
will fails unless a VIDIOC_S_FMT ioctl calls happens before the reqbufs.

But applications may first set the format and then attempt to determine
the I/O methods supported by the driver (for example Gstramer does it) so
the state won't be set to MFCINST_INIT again and VIDIOC_REQBUFS will fail.

To avoid this issue, only free the buffers on VIDIOC_REQBUFS(0) but don't
close the MFC instance to allow future VIDIOC_REQBUFS(n) calls to succeed.

Signed-off-by: ayaka <ayaka@xxxxxxxxxxx>
[javier: Rewrote changelog to explain the problem more detailed]
Signed-off-by: Javier Martinez Canillas <javier@xxxxxxxxxxxxxxx>


This is a resend of a patch posted by Ayaka some time ago [0].
Without $SUBJECT, trying to decode a video using Gstramer fails
on an Exynos5422 Odroid XU4 board with following error message:

$ gst-launch-1.0 filesrc location=test.mov ! qtdemux ! h264parse ! v4l2video0dec ! videoconvert ! autovideosink

Setting pipeline to PAUSED ...
Pipeline is PREROLLING ...
[ 3947.114756] vidioc_reqbufs:576: Only V4L2_MEMORY_MAP is supported
[ 3947.114771] vidioc_reqbufs:576: Only V4L2_MEMORY_MAP is supported
[ 3947.114903] reqbufs_output:484: Reqbufs called in an invalid state
[ 3947.114913] reqbufs_output:510: Failed allocating buffers for OUTPUT queue
ERROR: from element /GstPipeline:pipeline0/v4l2video0dec:v4l2video0dec0: Failed to allocate required memory.
Additional debug info:
gstv4l2videodec.c(575): gst_v4l2_video_dec_handle_frame (): /GstPipeline:pipeline0/v4l2video0dec:v4l2video0dec0:
Buffer pool activation failed
ERROR: pipeline doesn't want to preroll.
Setting pipeline to NULL ...
Freeing pipeline ...

[0]: https://patchwork.linuxtv.org/patch/32794/

Best regards,

drivers/media/platform/s5p-mfc/s5p_mfc_dec.c | 1 -
1 file changed, 1 deletion(-)

diff --git a/drivers/media/platform/s5p-mfc/s5p_mfc_dec.c b/drivers/media/platform/s5p-mfc/s5p_mfc_dec.c
index f2d6376ce618..8b9467de2d6a 100644
--- a/drivers/media/platform/s5p-mfc/s5p_mfc_dec.c
+++ b/drivers/media/platform/s5p-mfc/s5p_mfc_dec.c
@@ -474,7 +474,6 @@ static int reqbufs_output(struct s5p_mfc_dev *dev, struct s5p_mfc_ctx *ctx,
ret = vb2_reqbufs(&ctx->vq_src, reqbufs);
if (ret)
goto out;
- s5p_mfc_close_mfc_inst(dev, ctx);
ctx->src_bufs_cnt = 0;
ctx->output_state = QUEUE_FREE;
} else if (ctx->output_state == QUEUE_FREE) {