Re: [Linux-fbdev-users] who is writing to my framebuffer?

On Wed, 18 Oct 2006, Nathan King wrote:

> Hey folks,
>
> 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.
>
> Much thanks,
> Nathan

Sorry about the late reply. You are right. The cursor code uses a timer to 
blink the cursor. Is this a embedded system? You really don't need fbcon 
in that case.


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