Re: [PATCH v8 3/4] i2c: i801: add support of Host Notify

On Jun 09 2016 or thereabouts, Benjamin Tissoires wrote:

The i801 chip can handle the Host Notify feature since ICH 3 as mentioned
in http://www.intel.com/content/dam/doc/datasheet/82801ca-io-controller-hub-3-datasheet.pdf

Enable the functionality unconditionally and propagate the alert
on each notification.

With a T440s and a Synaptics touchpad that implements Host Notify, the
payload data is always 0x0000, so I am not sure if the device actually
sends the payload or if there is a problem regarding the implementation.

Tested-by: Andrew Duggan <redacted>
Acked-by: Wolfram Sang <redacted>
Signed-off-by: Benjamin Tissoires <redacted>
---
changes in v2:
- removed the description of the Slave functionality support in the chip table
  (the table shows what is supported, not what the hardware is capable of)
- use i2c-smbus to forward the notification
- remove the fifo, and directly retrieve the address and payload in the worker
- do not check for Host Notification is the feature is not enabled
- use inw_p() to read the payload instead of 2 inb_p() calls
- add /* fall-through */ comment
- unconditionally enable Host Notify if the hardware supports it (can be
  disabled by the user)
 
no changes in v3

changes in v4:
- make use of the new API -> no more worker spawning here
- solved a race between the access of the Host Notify registers and the actual
  I2C transfers.

changes in v5:
- added SKL Host Notify support

changes in v6:
- select I2C_SMBUS in Kconfig to prevent an undefined reference when I2C_I801
  is set to 'Y' while I2C_SMBUS is set to 'M'

no changes in v7

changes in v8:
- reapplied after http://patchwork.ozlabs.org/patch/632768/ and merged the
  conflict (minor conflict in the struct i801_priv).
- removed the .resume hook as upstream changed suspend/resume hooks and there
  is no need in the end to re-enable host notify on resume (tested on Lenovo
  t440 and t450).

Actually, this hook seemed to be required on the Lenovo T440 (Haswell)
but not on the T450 (Broadwell) laptop I have now here.

Wolfram, I can resend the whole series or a follow-up patch to re-enable
after resume Host Notify. How do you prefer I deal with that?

Cheers,
Benjamin