On Mon, Jun 11, 2012 at 06:46:14PM +0800, Liu Ying wrote:
> 2012/6/11, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>:
> > On Mon, Jun 11, 2012 at 09:06:48AM +0800, Liu Ying wrote:
> >> This patch checks if framebuffer is unblanked before
> >> we actually trigger panning in custom pan display
> >> function.
> >>
> >> Signed-off-by: Liu Ying <Ying.Liu@xxxxxxxxxxxxx>
> >> ---
> >> drivers/video/mx3fb.c | 5 +++++
> >> 1 files changed, 5 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/drivers/video/mx3fb.c b/drivers/video/mx3fb.c
> >> index e3406ab..d53db60 100644
> >> --- a/drivers/video/mx3fb.c
> >> +++ b/drivers/video/mx3fb.c
> >> @@ -1063,6 +1063,11 @@ static int mx3fb_pan_display(struct
> >> fb_var_screeninfo *var,
> >> dev_dbg(fbi->device, "%s [%c]\n", __func__,
> >> list_empty(&mx3_fbi->idmac_channel->queue) ? '-' : '+');
> >>
> >> + if (mx3_fbi->blank != FB_BLANK_UNBLANK) {
> >> + dev_dbg(fbi->device, "panning with fb blanked not supported\n");
> >> + return -EFAULT;
> >> + }
> >
> > Why is this an error, and why return -EFAULT? What userspace access
> > failed?
> >
> Hi, Russell,
>
> IMHO, panning with framebuffer blanked is meaningless, at least, it is
> not a common usecase.
Yes, but why should anything in userspace care whether the display is
blanked or not?
For example, we may pan the display when a user program produces output,
and we're on the last line of the display. We don't fail that just
because the screen happens to be blank. So I don't see why we should
actively fail an explicit userspace pan request just because the console
happened to be blanked.
What I'm basically saying is that as far as _userspace_ is concerned,
all the standard APIs should just work as normal whether the display is
blanked or not.
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