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
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