Hi Paul, On 03/31/2017 12:17 AM, Paul Menzel wrote:
Dear Wolfram,Thank you for the reply, which we talked about briefly at the Chemnitzer LinuxTage. Am Freitag, den 03.03.2017, 11:17 +0100 schrieb Wolfram Sang:Unfortunately, commit 2fee61d22e (i2c: piix4: Add support for multiplexed main adapter in SB800) [1] caused a regression. Tim reported that to the Linux Kernel Bugtracker as bug #170741 last September [2], but it looks like the affected subsystems don’t use it.Jean Delvare pointed out this issue amongst others[1] last year already. Let me quote: === 5* The I/O ports used for SMBus configuration and port switching are also needed by a watchdog driver, sp5100_tco. Both drivers request the region, so the first one wins, and the other driver can't be loaded. sp5100_tco was there first, so the changes done to the i2c-piix4 driver recently will cause a regression for some users by preventing them from using the sp5100_tco and i2c-piix4 drivers at the same time. In the long run I guess we will need a helper module to handle this shared resource. Unless IORESOURCE_MUXED can be used for that. Either way, that's more work than I can put into this before kernel v4.5 is released. For the time being, I think we should simply make it non-fatal if the I/O ports can't be requested, and continue without multiplexing (as before.) === Seems nobody had the resources, so far.I still don’t understand, why Jean then not immediately reverted the commit to adhere to the Linux Kernel’s no-regression-policy.I don't have the HW and not much experience with non-embedded platforms. I wonder, though, if we really need to convert the drivers to MFD ones, or if we could use the simpler MFD_SYSCON mechanism which helps in exactly such cases for embedded platforms. But I am really lacking details here and am afraid this is probably all the input I can give currently.Zoltan stepped up, and uploaded a patch for review to the Kernel.org Bugzilla [2], also attached to this message.
Please don't send patches as attachments.
request_muxed_region() can fail, and literally every other driver
using it checks for that failure. Please do the same.
The sp5100_tco_dev_name change in the watchdog driver is unnecessary.
There are some unnecessary { } in the watchdog driver after the patch
is applied.
Please split the patch into two patches so they can be reviewed and
applied separately.
Thanks,
Guenter
