Messages in this thread |  | | | Date | Mon, 11 Jun 2012 12:05:17 +0100 | | From | Russell King - ARM Linux <> | | Subject | Re: [PATCH 1/3] mx3fb: do not support panning with fb blanked |
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On Mon, Jun 11, 2012 at 06:46:14PM +0800, Liu Ying wrote: > 2012/6/11, Russell King - ARM Linux <linux@arm.linux.org.uk>: > > 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@freescale.com> > >> --- > >> 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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