Hi Arjan, On Fri, Sep 11, 2009 at 03:25:30PM +0200, Arjan Opmeer wrote: > > Recently I debugged a problem for a user where the Elantech touchpad of his > laptop chokes on the configuration values that the current kernel driver is > using. After sending a conflicting value the PS/2 controller freezes and > doesn't accept any subsequent bytes. > > The current configuration values for hardware version 2 (EeePC style) come > from the touchpad driver in the original Xandros Linux distribution for the > EeePC. And until now I haven't heard of problems with them. They look like > this: > > etd->reg_10 = 0x54; > etd->reg_11 = 0x88; > etd->reg_21 = 0x60; > > Some time ago I received the updated touchpad driver that is used in the > Dell mini Ubuntu distribution. Here the values are changed to be the same as > most of the Windows driver are using. Notice the difference in register 0x11 > and how they dropped configuring register 0x21: > > etd->reg_10 = 0x54; > etd->reg_11 = 0x8a; > > However for the laptop of the user mentioned above the values of his Windows > driver are like this: > > etd->reg_10 = 0x64; > etd->reg_11 = 0x8a; > > Notice the different values for registers 0x10 and 0x11 in comparison with > the current kernel driver. Also the registers _must_ be configured like > this. Using the current kernel driver values for either one of the registers > makes the touchpad freeze up. > > Remember that there isn't any publicly available documentation for the > hardware, so these configuration values are "black magic numbers" and the > only source of them is snooping what Windows drivers do or the source of > drivers in dedicated Linux distributions that happen to come my way. > > In all cases this is about touchpads with a firmware version reply of 0x02, > 0x00, 0x30. So even though the touchpad in this users laptops seems to be > the same as in the EeePC it really requires different values to be > configured. > > My question now is what is a prudent way to go forward? > > Is it OK that add a DMI check to the kernel driver that matches this users > laptop and dynamically adjust the configuration values? > I think adding some DMI rules to prevent the device lockup should be OK. > And how about the common case? Do we keep the values in the driver as they > are, or do we update them to the revised numbers as learned from the Ubuntu > driver? > I'd keep them as is at least for now, until we understand what exactly the change. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
