On Fri, Mar 17, 2017 at 05:57:52PM +0100, Daniel Vetter wrote:
On Fri, Mar 17, 2017 at 01:08:43PM +0200, Ville Syrjälä wrote:
On Fri, Mar 17, 2017 at 03:46:34PM +0530, Shirish S wrote:
On Fri, Mar 17, 2017 at 3:26 PM, Ville Syrjälä ville.syrjala@linux.intel.com wrote:
On Fri, Mar 17, 2017 at 01:25:08PM +0530, Shirish S wrote:
update_plane() and disable_plane() functions assoiciated with setting plane are called without any check, causing kernel panic.
Why are you registering a plane without the funcs?
Basically, enabling planes and making them fully functional is generally a 2 -step process, so i suggest for new drivers wanting to implement/re-design planes, would like to tap the flow at enabling(listing caps) and later at ensuring it works.
I don't think there's much point in exposing something that doesn't work. And even if you do, you could always just use stub functions.
Yes, just wire up stub functions if you want to enable planes with multi-step patch series.
I noticed that there is a underlying assumption only for plane->(funcs) are implemented, whereas for other function for crtc/connector/encoder function calls there is a sanity check(or WARN_ON) through out the framework.
I believe this check wont cause any performance/functional impact. Please let me know if am missing anything. And further more help developers to focus on enabling planes via various tests without causing reboots/system hangs.
I don't particularly like adding more unconditional runtime checks that just to protect developers from themselves. If you really think there's value in these, then at least add the checks into the plane init codepath so that it's a one time cost.
The same approach could be used for all the other non-optional hooks. Otherwise the same WARN_ON()s would have to be sprinkled all over the place, and there's always the risk of missing a few codepaths that call a specific hook.
I think for these here there's negative value - it allows developers to create completely broken planes. Stub functions really seem like a much better idea.
I was thinking
drm_whatever_init() { if (WARN_ON(!funcs->mandatory_thing)) return -EINVAL; }
rather than putting the WARN_ON()s around each call of funcs->mandatory_thing().
That will fail gracefully (which I guess is what people are after here), and gives the developer a clear message what's missing.