em28xx: some improvements

The first patch in this series change the em28xx to don't require coherent memory for DMA transfers. This should bring some performance gains on non-x86 archs.

The other patches in this series are results of my tests with the first patch :-)

patch 2 does some cleanups at i2c and Xclock speed settings.

Patches 3 and 4 do something that I'm intending to do for a long time: it constifies most static structs inside the driver. Before that, the cards list were modified in runtime, with is a bad idea when multiple (but different) boards use the same entry (for example, a webcam and a em28xx capture "generic" board).

Patch 5 solves a FIXME.

Patch 6 was written by Arnd, as a way to solve an issue with

KASAN: without it, more than 4Kbytes were spent at the stack,

with can cause very bad things. He sent it sometime ago.

As I answered when the patchset was sent, I didn't like very much that approach, as a way to solve KASAN, as the real solution is to improve the I2C binding logic inside this (and other) drivers. Yet, it brings a nice cleanup at em28xx.

So, patch 7 does that! It is something that I'm wanting to do for a long time, but only today I found the needed time: it adds helper functions at the DVB core in order to bind/unbind I2C modules to a driver. It is aligned with the new I2C binding work made by Antti.

Patch 8 converts em28xx-dvb to use the new dvb_module_probe() and dvb_module_release() fuctions, with caused a reduction of almost 10% on the size of this module!

A side effect of patches 7 and 8 is that we don't to use noinline_for_stack "black" magic there anymore, with is a good thing.

Arnd Bergmann (1):
media: em28xx: split up em28xx_dvb_init to reduce stack size

Mauro Carvalho Chehab (7):
media: em28xx: don't use coherent buffer for DMA transfers
media: em28xx: improve the logic with sets Xclk and I2C speed
media: em28xx: stop rewriting device's struct
media: em28xx: constify most static structs
media: em28xx: adjust I2C timeout according with I2C speed
media: dvb-core: add helper functions for I2C binding
media: em28xx-dvb: simplify DVB module probing logic

 drivers/media/dvb-core/dvbdev.c         |  48 ++
 drivers/media/usb/em28xx/em28xx-cards.c | 163 +++----
 drivers/media/usb/em28xx/em28xx-core.c  |  57 ++-
 drivers/media/usb/em28xx/em28xx-dvb.c   | 775 ++++++++++++--------------------
 drivers/media/usb/em28xx/em28xx-i2c.c   |  36 +-
 drivers/media/usb/em28xx/em28xx-input.c |   6 +-
 drivers/media/usb/em28xx/em28xx-video.c |  24 +-
 drivers/media/usb/em28xx/em28xx.h       |  39 +-
 include/media/dvbdev.h                  |  65 ++-
 9 files changed, 579 insertions(+), 634 deletions(-)

2.14.3