On Wed, 12 Feb 2014, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > On Wed, Feb 12, 2014 at 11:05:40AM +0800, Aaron Lu wrote: >> The ACPI table on ASUS UX302LA has more than 8 output devices under the >> graphics controller device node. The problem is, the real active output >> device, the LCD panel, is listed the last. The result is, the LCD's >> device id doesn't get recorded in the active device list CADL array and >> when the _DCS control method for the LCD device is executed, it returns >> 0x1d, meaning it is not active. This affects the hotkey delivery ASL >> code that will not deliver a notification if the output device is not >> active on backlight hotkey press. >> >> I don't see a clean way to solve this problem since the operation region >> spec doesn't allow more than 8 output devices so we have no way of >> storing all these output devices. The fact that output devices that have >> _BCM control method usually means they have a higher possibility of being >> used than those who don't made me choose a simple way to work around >> the buggy firmware by replacing the last entry in CADL array with the one >> that has _BCM control method. There is no specific reason why the last >> entry is picked instead of others. > > Another possibility is that the connector list is in rough priority > order so might be useful for sorting the CADL array. > > Since the CADL should only be a list of currently active devices, we > could just bite the bullet and repopulate it correctly after every > setcrtc. Agreed. Per spec, DIDL: Writes - Graphics driver writes to this field once during its initialization after determining platform supported connectors. CPDL: Writes - Graphics driver writes to this field on every monitor detection process. CADL: Writes - Graphics driver writes to this field on every mode set process and during boot. And for all of the above: Writes - System BIOS POST or ASL code should not write to these fields. BR, Jani. -- Jani Nikula, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
