I'm using a virtual framebuffer on some embedded hardware, and I'm trying to keep track of all changes to the framebuffer. I know when the three biggies, cfb_imageblit, cfb_fillrect, and cfb_copyarea write to it, but there's somebody else out there monkeying with it. These mystery writes happen during scrolling, which makes me think its somebody in fbcon. And I know its nothing from userspace, because this is happening during boot before we ever get to userspace. Is somebody in fbcon writing to my framebuffer behind my back?
My mystery writes ARE cursor sized (8x16 pixels). I can't find any, but do any cursor functions operate directly on info->screen_base, without going through one of cfb*?
What I'm seeing is that cfb_imageblit will receive a block of text from fbcon to draw at, say, (0,72), with a width of 64 pixels. Then the next block it receives is for (72,72). An eight pixel gap, and there should be some data between the two blocks. In fact if I look at the data after its finished with the line the data is somehow there. This happens at exactly the same locations every run.