svn commit: r348355 - head/sys/dev/iicbus

[Niclas Zeising]

On 2019-05-29 22:52, Ian Lepore wrote:
> On Wed, 2019-05-29 at 15:12 +0300, Andriy Gapon wrote:
>> On 29/05/2019 14:54, Niclas Zeising wrote:
>>> On 2019-05-29 11:08, Andriy Gapon wrote:
>>>> Author: avg
>>>> Date: Wed May 29 09:08:20 2019
>>>> New Revision: 348355
>>>> URL: https://svnweb.freebsd.org/changeset/base/348355
>>>>
>>>> Log:
>>>>     revert r273728 and parts of r306589, iicbus no-stop by default feature
>>>>        Since drm2 removal, there has not been any consumer of the feature in the
>>>>     tree.  I am also unaware of any out-of-tree consumer.
>>>>     More importantly, the feature has been broken from the very start, both
>>>>     before and after r306589, because the ivar was set on a device that does
>>>>     not support it and it was read from another device that also does not
>>>>     support it.
>>>>        A bus-wide no-stop flag cannot be implemented as an ivar as iicbus
>>>>     attaches as a child of various drivers.  Implementing the ivar in each
>>>>     and every I2C driver is just impractical.
>>>>        If we ever want to implement this feature properly, then probably the
>>>>     easiest way to do it would be via a flag in the softc of iicbus.
>>>>     In fact, we might have to do that in the stable branches if we want to
>>>>     fix the code for them.
>>>>        Reported by:    ian (long time ago)
>>>>     MFC after:    1 month (maybe)
>>>>     X-MFC-note:    cannot just merge the change, must keep drm2 happy
>>>>
>>>
>>> Hi!
>>> Just a note, be aware that drm2 lives on in ports as drm-legacy-kmod.  I haven't
>>> tested, but, from the description above I worry that it will affect the port.
>>> What do you think?
>>
>> Oh, I forgot about that one...
>> I think that it could be affected if it still uses FreeBSD iic code.
>> I guess I might have to revert the change.
>>
>>
> 
> I don't think so, because I don't think this change ever worked.  I'm
> not sure how anybody convinced themselves that it did.  It attempts to
> retrieve ivars from a device that doesn't have them, so the net effect
> is that the nostop variable is initialized from stack garbage.  Maybe
> whoever wrote and tested it was lucky enough to have that accidentally
> be consistently zero or non-zero, so their testing appeared to work.
> 
> Looking at the drm2 code that is the only user of this, it appears that
> the nostop value is only used in the case where the driver falls back
> to using the builtin intel_iicbb_driver.  That driver relies on
> iicbus_transfer_gen() which is where the nostop kludge was added.
> That's the fundamental problem in all of this:  the right thing to do,
> IMO, would have been to implement the iicbus_transfer method directly
> in the intel_iicbb_driver (probably by just cut-and-pasting the code
> from iicconf.c then doing whatever is necessary to ignore stops).  And
> we can still do that, pretty trivially, if necessary.
> 
> -- Ian
> 


Hi!
It seems like things broke after all, latest pkg build (on head-amd64) 
reports this:


/wrkdirs/usr/ports/graphics/drm-legacy-kmod/work/drm-legacy-12bd551/src/dev/drm2/i915/intel_iic.c:570:2: 
error: implicit declaration of function 'iicbus_set_nostop' is invalid 
in C99 [-Werror,-Wimplicit-function-declaration]
         iicbus_set_nostop(idev, true);
         ^
/wrkdirs/usr/ports/graphics/drm-legacy-kmod/work/drm-legacy-12bd551/src/dev/drm2/i915/intel_iic.c:570:2: 
error: this function declaration is not a prototype 
[-Werror,-Wstrict-prototypes]
2 errors generated.

Full log:

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p503023_s348376/logs/drm-legacy-kmod-g20190523.log

Regards
-- 
Niclas Zeising