xref: /linux/Documentation/fb/metronomefb.rst (revision 0898782247ae533d1f4e47a06bc5d4870931b284)
1===========
2Metronomefb
3===========
4
5Maintained by Jaya Kumar <jayakumar.lkml.gmail.com>
6
7Last revised: Mar 10, 2008
8
9Metronomefb is a driver for the Metronome display controller. The controller
10is from E-Ink Corporation. It is intended to be used to drive the E-Ink
11Vizplex display media. E-Ink hosts some details of this controller and the
12display media here http://www.e-ink.com/products/matrix/metronome.html .
13
14Metronome is interfaced to the host CPU through the AMLCD interface. The
15host CPU generates the control information and the image in a framebuffer
16which is then delivered to the AMLCD interface by a host specific method.
17The display and error status are each pulled through individual GPIOs.
18
19Metronomefb is platform independent and depends on a board specific driver
20to do all physical IO work. Currently, an example is implemented for the
21PXA board used in the AM-200 EPD devkit. This example is am200epd.c
22
23Metronomefb requires waveform information which is delivered via the AMLCD
24interface to the metronome controller. The waveform information is expected to
25be delivered from userspace via the firmware class interface. The waveform file
26can be compressed as long as your udev or hotplug script is aware of the need
27to uncompress it before delivering it. metronomefb will ask for metronome.wbf
28which would typically go into /lib/firmware/metronome.wbf depending on your
29udev/hotplug setup. I have only tested with a single waveform file which was
30originally labeled 23P01201_60_WT0107_MTC. I do not know what it stands for.
31Caution should be exercised when manipulating the waveform as there may be
32a possibility that it could have some permanent effects on the display media.
33I neither have access to nor know exactly what the waveform does in terms of
34the physical media.
35
36Metronomefb uses the deferred IO interface so that it can provide a memory
37mappable frame buffer. It has been tested with tinyx (Xfbdev). It is known
38to work at this time with xeyes, xclock, xloadimage, xpdf.
39