There are two types of swapping the EEPROM data in the ath9k driver.
Before this series one type of swapping could not be used without the
other.

The first type of swapping looks at the "magic bytes" at the start of
the EEPROM data and performs swab16 on the EEPROM contents if needed.
The second type of swapping is EEPROM format specific and swaps
specific fields within the EEPROM itself (swab16, swab32 - depends on
the EEPROM format).

With this series the second part now looks at the EEPMISC register
inside the EEPROM, which uses a bit to indicate if the EEPROM data
is Big Endian (this is also done by the FreeBSD kernel).
This has a nice advantage: currently there are some out-of-tree hacks
(in OpenWrt and LEDE) where the EEPROM has a Big Endian header on a
Big Endian system (= no swab16 is performed) but the EEPROM itself
indicates that it's data is Little Endian. Until now the out-of-tree
code simply did a swab16 before passing the data to ath9k, so ath9k
first did the swab16 - this also enabled the format specific swapping.
These out-of-tree hacks are still working with the new logic, but it
is recommended to remove them. This implementation is based on a
discussion with Arnd Bergmann who raised concerns about the
robustness and portability of the swapping logic in the original OF
support patch review, see [0].

After a second round of patches (= v1 of this series) neither Arnd
Bergmann nor I were really happy with the complexity of the EEPROM
swapping logic. Based on a discussion (see [1] and [2]) we decided
that ath9k should use a defined format (specifying the endianness
of the data - I went with __le16 and __le32) when accessing the
EEPROM fields. A benefit of this is that we enable the EEPMISC based
swapping logic by default, just like the FreeBSD driver, see [3]. On
the devices which I have tested (see below) ath9k now works without
having to specify the "endian_check" field in ath9k_platform_data (or
a similar logic which could provide this via devicetree) as ath9k now
detects the endianness automatically. Only EEPROMs which are mangled
by some out-of-tree code still need the endian_check flag (or one can
simply remove that mangling from the out-of-tree code).

Testing:
- tested by myself on AR9287 with Big Endian EEPROM
- tested by myself on AR9227 with Little Endian EEPROM
- tested by myself on AR9381 (using the ar9003_eeprom implementation,
  which did not suffer from this whole problem)
- how do we proceed with testing? maybe we could keep this in a
  feature-branch and add these patches to LEDE once we have an ACK to
  get more people to test this

This series depends on my other series (v7):
"add devicetree support to ath9k" - see [4]

Changes since v1:
- reworked description in the cover-letter to describe the reasons
  behind the new patch 7
- reworked patch "Set the "big endian" bit of the AR9003 EEPROM
  templates" as ar9003_eeprom.c sets all values as Little Endian, thus
  the Big Endian bit should never be set (the new patch makes this
  clear)
- dropped "ath9k: Make EEPROM endianness swapping configurable via
  devicetree" as it is not needed anymore with the new logic from
  patch 7
- added patches 4 and 5 as small cleanup (this made it easier to
  implement the le{16,32}_to_cpu() changes where needed)


[0] http://www.spinics.net/lists/linux-wireless/msg152634.html
[1] https://marc.info/?l=linux-wireless&m=147250597503174&w=2
[2] https://marc.info/?l=linux-wireless&m=147254388611344&w=2
[3] 
https://github.com/freebsd/freebsd/blob/50719b56d9ce8d7d4beb53b16e9edb2e9a4a7a18/sys/dev/ath/ath_hal/ah_eeprom_9287.c#L351
[4] https://marc.info/?l=linux-wireless&m=147544488619822&w=2

Martin Blumenstingl (7):
  ath9k: Add a #define for the EEPROM "eepmisc" endianness bit
  ath9k: indicate that the AR9003 EEPROM template values are little
    endian
  ath9k: Add an eeprom_ops callback for retrieving the eepmisc value
  ath9k: replace eeprom_param EEP_MINOR_REV with get_eeprom_rev
  ath9k: consistently use get_eeprom_rev(ah)
  ath9k: Make the EEPROM swapping check use the eepmisc register
  ath9k: define all EEPROM fields in Little Endian format

 drivers/net/wireless/ath/ath9k/ar5008_phy.c    |   2 +-
 drivers/net/wireless/ath/ath9k/ar9002_hw.c     |   6 +-
 drivers/net/wireless/ath/ath9k/ar9003_eeprom.c |  21 ++--
 drivers/net/wireless/ath/ath9k/ar9003_eeprom.h |   4 +-
 drivers/net/wireless/ath/ath9k/eeprom.c        |  42 ++++---
 drivers/net/wireless/ath/ath9k/eeprom.h        |  85 +++++++------
 drivers/net/wireless/ath/ath9k/eeprom_4k.c     | 137 +++++++++------------
 drivers/net/wireless/ath/ath9k/eeprom_9287.c   | 129 +++++++++----------
 drivers/net/wireless/ath/ath9k/eeprom_def.c    | 163 ++++++++++++-------------
 drivers/net/wireless/ath/ath9k/xmit.c          |   3 +-
 10 files changed, 289 insertions(+), 303 deletions(-)

-- 
2.10.0

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