Re: Enumerating available display modes?

Re: Enumerating available display modes?

[Kendall Bennett]

Jon Smirl <jonsmirl@yahoo.com> wrote:

> I just scanned a couple of the fbdrivers and there seems to be no
> way to enumerate the modes that the hardware can support. This
> feature is probably lacking since there was no real use for it
> without the DDC monitor info. 

Well without the DDC monitor info you cannot ensure that modes the 
hardware can support will work on the attached monitor, but it is better 
than now knowing what modes are available anyway. As it stands right now, 
apps can simply call into the driver and 'try' to set any more that might 
be supported, but good luck knowing if it will or if the monitor can 
handle it.

Also IMHO it is not a good idea to expect apps to pass down the CRTC and 
pixel clock timings for the graphics card. It is nice to have this 
programmable interface, but user land apps really just want to set a mode 
and not have to deal with that stuff. Rarely they even care about the 
refresh rate (just use a good one for the attached monitor).

> The fb modes are controlled via /etc/fb.modes 

How do you mean they are controlled by /etc/fb.modes?

> On the other hand, the X windows drivers know how to enumerate the
> hardware supported modes. Just look at your XFree log and you can
> see a list of card supported modes vs monitor supported modes, and
> finally the pairs that match. 

Yes, I am aware that XFree86 drivers can do this.

> The solution is to go lift the appropriate code out of the X
> windows drivers and add it to the fb ones. 

Actually IMHO a better solution is the vesafbd project, since it would 
allow framebuffer console drivers to be developed in user land, and could 
then use the existing XFree86 driver modules without having to 'port' 
them to the Linux kernel. Also with the vesafbd project it will be 
possible to add support for reading the complete EDID from the monitor 
using the VESA BIOS functions, so that the vesa framebuffer console 
driver *could* know about the attached monitor and filter the available 
modes that the VESA BIOS supports for the user applications.

Regards,

---
Kendall Bennett
Chief Executive Officer
SciTech Software, Inc.
Phone: (530) 894 8400
http://www.scitechsoft.com

~ SciTech SNAP - The future of device driver technology! ~



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Re: fb_imageblit semantic

[Antonino Daplas]

On Mon, 2003-03-17 at 21:47, Geert Uytterhoeven wrote:
>
> IMHO always using an image depth of 8 is fine. That's a nice trade off between
> genericity and easy access of image data.
> 
> Except for monochrome, there I prefer a depth of 1, since doing 1->8 and 8->1
> in a row is a bit too wasteful.
> 

An exception to the rule :-)  Well, I guess if it will significantly
benefit monochrome drivers...

> BTW, I just realized there's no need to distinguish between monochrome copy and
> monochrome-to-color expansion. The monochrome logo code just has to write the
> correct values to fb_image.[fb]gcolor. I.e. all zeroes or all ones (number of
> bits = var.bits_per_pixel, so it works for 8-bit monochrome, too).
> 

I remember mentioning this to you before, and you said that there might
be rare cases that fgcolor can be equal to bgcolor.  However, using -1
instead for bg_color/fg_color may work, at least for the current setup
and only for monochrome, (except perhaps 32-bit monochrome, if there is
such a thing)

I still prefer splitting fb_imageblit() into two though, and still keep
image->depth for logo drawing only, to allow for future expansion.
. 
> > Do we still use the LUT?  
> 
> Yes. An alternative is to enlarge the pseudo palette to 256 entries (if there

Yes.  Which also means logo drawing will also work for quirky drivers,
and the upper layer will be finally totally independent of the low level
drivers.

> are enough number of colors). But since imageblit is done for the logo only,
> doing the transform from LUT index to pixel value in imageblit is OK, I think.
> 

Yes, I also prefer referring to the LUT whatever the format even for
character drawing.  I don't expect any noticeable performance penalty
except for logo drawing.  The way it's currently done is because,
looking at all drivers, not one fills up the pseudo_palette when bpp <=
8.

Tony



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Detecting if the mode can be changed?

[Kendall Bennett]

Hi Guys,

I am working on implementing code to use the framebuffer console, and I 
want to know in advance of calling FBIOPUT_VSCREENINFO if the screen 
resolution and color depth can actually be changed at runtime or not. If 
the VESA driver is running, this ioctl() displays an error message on the 
screen, and I want to avoid this error message by knowing in advance if 
the ioctl() will work or not.

Is there a flag or way to determine this?

Regards,

---
Kendall Bennett
Chief Executive Officer
SciTech Software, Inc.
Phone: (530) 894 8400
http://www.scitechsoft.com

~ SciTech SNAP - The future of device driver technology! ~



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Enumerating available display modes?

[Kendall Bennett]

Hi Again,

In working with the framebuffer console interface, it does not appear to 
support enumerating what display modes are available to be set via the 
/dev/fb interface. Am I right in thinking this, or am I missing something 
in the API? I am going to take a look at the source code, but some high 
level programming information would be well received at this end ;-)

Also I can't seem to find any code related to acceleration via /dev/fb. 
Is this not possible for user land apps to call the acceleration 
functions in /dev/fb? I guess I can check the XFree86 module to see how 
it does it....

Regards,

---
Kendall Bennett
Chief Executive Officer
SciTech Software, Inc.
Phone: (530) 894 8400
http://www.scitechsoft.com

~ SciTech SNAP - The future of device driver technology! ~



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