X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=Documentation%2Ffb%2Fpxafb.txt;h=d143a0a749f9ff3d975e7d0f62b89bb05c0e0620;hb=a1d1c11c3d74677c210fb1a2db4dbeb239dc6d49;hp=db9b8500b43b01cd62841d7c7b6ff1650b2829a1;hpb=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2;p=pandora-kernel.git

diff --git a/Documentation/fb/pxafb.txt b/Documentation/fb/pxafb.txt
index db9b8500b43b..d143a0a749f9 100644
--- a/Documentation/fb/pxafb.txt
+++ b/Documentation/fb/pxafb.txt
@@ -5,9 +5,13 @@ The driver supports the following options, either via
 options=<OPTIONS> when modular or video=pxafb:<OPTIONS> when built in.
 
 For example:
-	modprobe pxafb options=mode:640x480-8,passive
+	modprobe pxafb options=vmem:2M,mode:640x480-8,passive
 or on the kernel command line
-	video=pxafb:mode:640x480-8,passive
+	video=pxafb:vmem:2M,mode:640x480-8,passive
+
+vmem: VIDEO_MEM_SIZE
+	Amount of video memory to allocate (can be suffixed with K or M
+	for kilobytes or megabytes)
 
 mode:XRESxYRES[-BPP]
 	XRES == LCCR1_PPL + 1
@@ -52,3 +56,87 @@ outputen:POLARITY
 pixclockpol:POLARITY
 	pixel clock polarity
 	0 => falling edge, 1 => rising edge
+
+
+Overlay Support for PXA27x and later LCD controllers
+====================================================
+
+  PXA27x and later processors support overlay1 and overlay2 on-top of the
+  base framebuffer (although under-neath the base is also possible). They
+  support palette and no-palette RGB formats, as well as YUV formats (only
+  available on overlay2). These overlays have dedicated DMA channels and
+  behave in a similar way as a framebuffer.
+
+  However, there are some differences between these overlay framebuffers
+  and normal framebuffers, as listed below:
+
+  1. overlay can start at a 32-bit word aligned position within the base
+     framebuffer, which means they have a start (x, y). This information
+     is encoded into var->nonstd (no, var->xoffset and var->yoffset are
+     not for such purpose).
+
+  2. overlay framebuffer is allocated dynamically according to specified
+     'struct fb_var_screeninfo', the amount is decided by:
+
+        var->xres_virtual * var->yres_virtual * bpp
+
+     bpp = 16 -- for RGB565 or RGBT555
+         = 24 -- for YUV444 packed
+         = 24 -- for YUV444 planar
+	 = 16 -- for YUV422 planar (1 pixel = 1 Y + 1/2 Cb + 1/2 Cr)
+	 = 12 -- for YUV420 planar (1 pixel = 1 Y + 1/4 Cb + 1/4 Cr)
+
+     NOTE:
+
+     a. overlay does not support panning in x-direction, thus
+        var->xres_virtual will always be equal to var->xres
+
+     b. line length of overlay(s) must be on a 32-bit word boundary,
+        for YUV planar modes, it is a requirement for the component
+	with minimum bits per pixel,  e.g. for YUV420, Cr component
+	for one pixel is actually 2-bits, it means the line length
+	should be a multiple of 16-pixels
+
+     c. starting horizontal position (XPOS) should start on a 32-bit
+        word boundary, otherwise the fb_check_var() will just fail.
+
+     d. the rectangle of the overlay should be within the base plane,
+        otherwise fail
+
+     Applications should follow the sequence below to operate an overlay
+     framebuffer:
+
+         a. open("/dev/fb[1-2]", ...)
+	 b. ioctl(fd, FBIOGET_VSCREENINFO, ...)
+	 c. modify 'var' with desired parameters:
+	    1) var->xres and var->yres
+	    2) larger var->yres_virtual if more memory is required,
+	       usually for double-buffering
+	    3) var->nonstd for starting (x, y) and color format
+	    4) var->{red, green, blue, transp} if RGB mode is to be used
+	 d. ioctl(fd, FBIOPUT_VSCREENINFO, ...)
+	 e. ioctl(fd, FBIOGET_FSCREENINFO, ...)
+	 f. mmap
+	 g. ...
+
+  3. for YUV planar formats, these are actually not supported within the
+     framebuffer framework, application has to take care of the offsets
+     and lengths of each component within the framebuffer.
+
+  4. var->nonstd is used to pass starting (x, y) position and color format,
+     the detailed bit fields are shown below:
+
+    31                23  20         10          0
+     +-----------------+---+----------+----------+
+     |  ... unused ... |FOR|   XPOS   |   YPOS   |
+     +-----------------+---+----------+----------+
+
+     FOR  - color format, as defined by OVERLAY_FORMAT_* in pxafb.h
+            0 - RGB
+	    1 - YUV444 PACKED
+	    2 - YUV444 PLANAR
+	    3 - YUV422 PLANAR
+	    4 - YUR420 PLANAR
+
+     XPOS - starting horizontal position
+     YPOS - starting vertical position