On Wed, 2011-09-14 at 17:50 +0530, K, Mythri P wrote: > Hi, > > On Wed, Sep 14, 2011 at 2:27 PM, Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote: > > On Wed, 2011-09-14 at 14:18 +0530, K, Mythri P wrote: > >> On Wed, Sep 14, 2011 at 2:04 PM, Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote: > >> > On Wed, 2011-09-14 at 13:57 +0530, K, Mythri P wrote: > >> >> On Wed, Sep 14, 2011 at 12:44 PM, Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote: > > > > <snip> > > > >> > I don't understand this one. How could this be more dynamic? The > >> > function checks the HPD bit, which (based on my observation) shows the > >> > status whether a display is connected or not. > >> There is a GPIO which detects the +3.3V on the line and detects the > >> cable connect , there is also an interrupt based way.This is ideally > >> called a Hot-plug detect event according to the spec in HDMI terms. > >> But what you are saying here is that it is just a poll on the state? > > > > Yes, it's just for polling, but I don't quite see the difference. A > > hot-plug event notifies when the display is connected or disconnected, > > and detect() tells if a display is connected. They are all about the > > same thing. > > > >> >> So I said if the purpose of this function is only to check for the HPD > >> >> state bit it is fine. > >> > > >> > What does HPD bit tell us then? > >> > >> HPD state bit tells whether the cable is connected and whether EDID is > > > > This sounds like a good bit to test then. So is there something wrong > > with using HPD? How does the GPIO differ from HPD bit? > > > >> ready to be read, But this is a static check that is done in this > >> function. > > > > I don't understand what you mean with "static". The bit changes > > dynamically according to the connect/disconnect state, and the bit is > > checked dynamically when detect() is called. > > > Well ! Who would call the detect and why ? By Dynamic i meant when the > cable is physically disconnected and connected there is detection > logic which can be implemented either by GPIo/Interrupts. > When you say the cable is connected , what happens in this case when > the cable is connected to say monitor of one resolution and then > plugged out and put to the other. Instead with dynamic method the > based on the physical connect and disconnect the notification would be > sent to any listener. Ok, I see now what you mean. Yes, you are right, detect() does not "know" if the monitor has changed between polls, so both notification and polling are needed. I implemented only polling as there's no HPD event mechanism yet in omapdss, and also because this was simple and gives DRM basic ability to detect a monitor. Tomi -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
