[PATCH 0/8] fbcon: Console Rotation

[PATCH 0/8] fbcon: Console Rotation

[Antonino A. Daplas]

This patch series implements generic code to rotate the console at 90, 180,
and 270 degrees. The implementation is completely done in the framebuffer
console level, thus no changes to the framebuffer layer or to the drivers
are needed.

Console rotation is required by some Sharp-based devices where the natural
orientation of the display is not at 0 degrees. Also, users that have
displays that can pivot will benefit by having a console in portrait mode
if they so desire.

The choice to implement the code in the console layer rather than in the
framebuffer layer is due to the following reasons:

- it's fast
- it does not require driver changes
- it can coexist with devices that can rotate the display at the hardware level
- it complements graphics applications that can do display rotation

The changes to core fbcon are minimal-- recognition of the console
rotation angle so it can swap directions, origins and axes (xres vs yres,
xpanstep vs ypanstep, xoffset vs yoffset, etc) and storage of the rotation
angle per display. The bulk of the code that does the actual drawing to the
screen are placed in separate files. Each angle of rotation has separate
methods (bmove, clear, putcs, cursor, update_start which is derived from
update_var, and clear_margins).  To mimimize processing time, the fontdata
are pre-rotated at each console switch (only if the font or the angle has
changed). 

The option can be compiled out (CONFIG_FRAMEBUFFER_CONSOLE_ROTATION = n) if
rotation is not needed. 

Choosing the rotation angle can be done in several ways:

1. boot option fbcon=rotate:n, where
     n = 0 - normal
     n = 1 - 90 degrees (clockwise)
     n = 2 - 180 degrees (upside down)
     n = 3 - 270 degrees (counterclockwise)

2. echo n > /sys/class/graphics/fb[num]/con_rotate
 
     where n is the same as described above. It sets the angle of rotation
of the current console

3 echo n > /sys/class/graphics/fb[num]/con_rotate_all

     where n is the same as described above. Globally sets the angle of
rotation.

GOTCHAS:

	The option, especially at angles of 90 and 270 degrees, will exercise
the least used code of drivers.  Namely, at these angles, panning is done
in the x-axis, so it can reveal bugs in the driver if xpanstep is set
incorrectly. A workaround is to set xpanstep = 0.

	Secondly, at these angles, the framebuffer memory access can be
unaligned if (fontheight * bpp) % 32 ~= 0 which can reveal bugs in the drivers
imageblit, fillrect and copyarea functions.  (I think cfbfillrect may have
this buglet). A workaround is to use a standard 8x16 font.

Speed:

	The scrolling speed difference between 0 and 180 degrees is minimal,
somewhere areound 1-2%.  At 90 or 270 degress, speed drops down to a vicinity
of 30-40%. This is understandable because the blit direction is across the
framebuffer "direction." Scrolling will be helped at these angles if xpanstep
is not equal to zero, use of 8x16 fonts, and setting xres_virtual >= xres * 2.

Note: The code is tested on little-endian only, so I don't know if it will
work in big-endian. Please let me know, it will take only less than a minute
of your time.

Tony



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Re: [PATCH 0/8] fbcon: Console Rotation

[Andrew Morton]

"Antonino A. Daplas" <adaplas@gmail.com> wrote:
>
> This patch series implements generic code to rotate the console at 90, 180,
> and 270 degrees.

I note that you have a bunch of fixes which are dependent upon these changes.

What's your priority on all this work?


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Re: [PATCH 0/8] fbcon: Console Rotation

[Antonino A. Daplas]

Andrew Morton wrote:
> "Antonino A. Daplas" <adaplas@gmail.com> wrote:
>> This patch series implements generic code to rotate the console at 90, 180,
>> and 270 degrees.
> 
> I note that you have a bunch of fixes which are dependent upon these changes.
> 
> What's your priority on all this work?
> 

None are actually important, except for these 2 which are fixes of
real problems:

[PATCH 1/7] savagefb: X-panning fixes
[PATCH 7/7] fbdev: Framebuffer mode required for PowerBook Titanium

These 2 should apply cleanly.

The rest are cleanups and can wait.  If you have problems merging them,
I'll resubmit them on your next release.

Tony


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Re: [PATCH 0/8] fbcon: Console Rotation

[Andrew Morton]

"Antonino A. Daplas" <adaplas@gmail.com> wrote:
>
> Andrew Morton wrote:
> > "Antonino A. Daplas" <adaplas@gmail.com> wrote:
> >> This patch series implements generic code to rotate the console at 90, 180,
> >> and 270 degrees.
> > 
> > I note that you have a bunch of fixes which are dependent upon these changes.
> > 
> > What's your priority on all this work?
> > 
> 
> None are actually important, except for these 2 which are fixes of
> real problems:
> 
> [PATCH 1/7] savagefb: X-panning fixes
> [PATCH 7/7] fbdev: Framebuffer mode required for PowerBook Titanium
> 
> These 2 should apply cleanly.

OK.

> The rest are cleanups and can wait.

Well I was also referring to the rotation patches - a new feature.

I guess you'd like them in 2.6.15.  Ho hum.



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Re: [PATCH 0/8] fbcon: Console Rotation

[Antonino A. Daplas]

Andrew Morton wrote:
> "Antonino A. Daplas" <adaplas@gmail.com> wrote:
>> Andrew Morton wrote:
>>> "Antonino A. Daplas" <adaplas@gmail.com> wrote:
>> The rest are cleanups and can wait.
> 
> Well I was also referring to the rotation patches - a new feature.
> 
> I guess you'd like them in 2.6.15.  Ho hum.
> 

Not really, I already had a patch much similar to this since 2.5.x,
but never pushed it, so it can wait a few kernel versions. I would
rather that they get the testing for as long as possible. It's the
Zaurus people that may actually want this feature just because they
need it, but I believe they have their own development kernel with
this patch already included.

Unfortunately though, this patch substantially changed fbcon.c, so
any other patch affecting that file may have to wait or risk
conflicts in the future.

Tony 
 



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Re: [PATCH 0/8] fbcon: Console Rotation

[Andrew Morton]

"Antonino A. Daplas" <adaplas@gmail.com> wrote:
>
> Unfortunately though, this patch substantially changed fbcon.c, so
>  any other patch affecting that file may have to wait or risk
>  conflicts in the future.

Yes, that's a problem.  We _could_ just slam this in this week and grit our
teeth.  How would you evaluate the risk of regressions to existing setups?


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Re: [PATCH 0/8] fbcon: Console Rotation

[Antonino Daplas]

On 11/8/05, Andrew Morton <akpm@osdl.org> wrote:
> "Antonino A. Daplas" <adaplas@gmail.com> wrote:
> >
> > Unfortunately though, this patch substantially changed fbcon.c, so
> >  any other patch affecting that file may have to wait or risk
> >  conflicts in the future.
>
> Yes, that's a problem.  We _could_ just slam this in this week and grit our
> teeth.  How would you evaluate the risk of regressions to existing setups?

Low, if rotation is disabled. Most of the rotation code will be
compiled as no-ops.

Tony


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Re: [PATCH 0/8] fbcon: Console Rotation

[Andrew Morton]

Antonino Daplas <adaplas@gmail.com> wrote:
>
> On 11/8/05, Andrew Morton <akpm@osdl.org> wrote:
> > "Antonino A. Daplas" <adaplas@gmail.com> wrote:
> > >
> > > Unfortunately though, this patch substantially changed fbcon.c, so
> > >  any other patch affecting that file may have to wait or risk
> > >  conflicts in the future.
> >
> > Yes, that's a problem.  We _could_ just slam this in this week and grit our
> > teeth.  How would you evaluate the risk of regressions to existing setups?
> 
> Low, if rotation is disabled. Most of the rotation code will be
> compiled as no-ops.

Ho hum, OK.  Fingers crossed...


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Re: Re: [PATCH 0/8] fbcon: Console Rotation

[Knut Petersen]

>>>>Unfortunately though, this patch substantially changed fbcon.c, so
>>>> any other patch affecting that file may have to wait or risk
>>>> conflicts in the future.
>>>>        
>>>>
>>>Yes, that's a problem.  We _could_ just slam this in this week and grit our
>>>teeth.  How would you evaluate the risk of regressions to existing setups?
>>>      
>>>
>>Low, if rotation is disabled. Most of the rotation code will be
>>compiled as no-ops.
>>    
>>
>
>Ho hum, OK.  Fingers crossed...
>
>  
>
If those patches would introduce bugs not related to rotated screens we 
would
find those bugs quickly as every single user tests those routines at 
least during
the boot process.

Screen rotation is a usefull feature. Not for everybody, but there are 
lots of people
who would appreciate it. I vote for including them now, asap. This would 
give the
maintainers of the hardware drivers a real argument to fix x-panning, or 
at least to
disable it in *check_var()  in case it is broken or not supported by the 
hardware.

cu,
 knut




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