Android 6.0 Marshmallow, formerly known as Android M, is beginning to roll out to non-Nexus devices in fits and starts. Now OnePlus has revealed the U.S. Android M OTA update release date window for its cult-hit devices, the OnePlus One and OnePlus Two. There's also an official update on the progress of Android Marshmallow on the new OnePlus X.

The OnePlus One and OnePlus 2 run two different operating systems, giving users a choice between the techy favorite Cyanogen OS or OnePlus's very own Oxygen OS. Both are custom variants of stock Android, and both are pretty close to the pure Android experience, which is one of the reasons why the Chinese device-maker owned by Oppo is such a hit with the Android geek community.

Another reason? OnePlus is pretty fast pushing out operating system updates to its devices. And that remains true for the Android 6.0 Marshmallow-based updates the company recently announced for the OnePlus One and OnePlus Two.

OnePlus announced on its community forums this week (via Android Police) that both the OnePlus One and OnePlus 2 were scheduled to get Android 6.0 Marshmallow in the first part of 2016.

The company went into detail about the Cyanogen OS and Oxygen OS updates on the way, though it wouldn't specify exactly when in Q1 of 2016 OnePlus owners should begin expecting OTA update notifications.

"For the OnePlus One, Cyanogen OS will be updating to Marshmallow in the first quarter of 2016," stated OnePlus's Android M update announcement. "We will be updating the community build of OxygenOS for the OnePlus One when time allows," continued the company's statement.

The OnePlus 2, meanwhile, is scheduled to be updated in the first quarter of 2016 as well, and the update will include Android 6.0 Marshmallow's support for the device's built-in fingerprint scanner.

That built-in fingerprint scanner support won't be coming to OxygenOS on the OnePlus 2, however. As OnePlus stated, "We've heard requests for us creating an API for the current fingerprint implementation in OxygenOS, but have decided against this since we're switching over to the standard Android M implementation soon."

As for the OnePlus X, the company said the Android 6.0 Marshmallow update would be on the way "as soon as possible," but added that it didn't have a time frame yet to announce.

OnePlus did, however, post the open source kernel code for the OxygenOS v2 for the OnePlus X on GitHub.

OnePlus recently began pushing the latest OxygenOS update (version 2.1.1) OTA for the OnePlus 2 and OnePlus X, which includes improved performance on application installations and launches, some bug fixes and security patches, as well as an improved UI for previews in the stock camera app.