Thread (1 message) 1 message, 1 author, 2006-11-13

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

From: James Simmons <hidden>
Date: 2006-11-13 17:10:29

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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