Improve DVB memory mapped API

This series improve the DVB memory mapped API to allow it to report continuity errors.

Doing it for Digital TV standards is not mandatory, as MPEG-TS has already support for it. Yet, when trying to discover if the discontinuity happened due to a driver problem or due to userspace troubles can be tricky.

So, this patch series add two fields at the struct used by DMX_DQBUF (struct dmx_buffer):

- count: a simple monotonic uint32_t counter;
- flags: a bitmap field that lets the DVB core to report if it detects an error.

There are already some logic inside the demux code that checks for discontinuity errors while receiving data. Make them to update the flags.

Somehow, some changes I made while testing the DVB API never made upstream: Arnd had to write some fixes for it to be built and parts of the conditional support had a reverted logic.

patch 1 actually addresses an old issue at the DVB demux API:
if an ioctl fails due to invalid parameters, or if an ioctl doesn't exist, it returns the same error code (-EINVAL). The patch changes the latter to -ENOTTY>

patch 2 fixes the DMA mmap support, that was merged lacking a fix that got lost. I ended by rewriting the code, making it simpler.

patch 3 adds count/flags to mmap API;

patch 4 makes the DVB core to update count and flags.

All those patches are at:
https://git.linuxtv.org/mchehab/experimental.git/log/?h=dvb-mmap-v3

The v4l-utils code, updated to use the mmap API, is at:
https://git.linuxtv.org/mchehab/experimental-v4l-utils.git/log/?h=dvb-mmap-v2

Please notice that the API is experimental, and may still change until we release the final version of Kernel 4.16.

Have fun,
Mauro

Mauro Carvalho Chehab (4):
media: dmxdev: fix error code for invalid ioctls
media: dmxdev: Fix the logic that enables DMA mmap support
media: dvb: add continuity error indicators for memory mapped buffers
media: dvb: update buffer mmaped flags and frame counter

 Documentation/media/dmx.h.rst.exceptions  |  14 ++--
 Documentation/media/uapi/dvb/dmx-qbuf.rst |   7 +-
 drivers/media/dvb-core/dmxdev.c           |  98 +++++++++++++++-----------
 drivers/media/dvb-core/dvb_demux.c        | 113 +++++++++++++++++++-----------
 drivers/media/dvb-core/dvb_net.c          |   5 +-
 drivers/media/dvb-core/dvb_vb2.c          |  31 +++++---
 include/media/demux.h                     |  21 ++++--
 include/media/dmxdev.h                    |   2 +
 include/media/dvb_demux.h                 |   4 ++
 include/media/dvb_vb2.h                   |  18 ++++-
 include/uapi/linux/dvb/dmx.h              |  35 +++++++++
 11 files changed, 242 insertions(+), 106 deletions(-)

2.14.3