Implementing new fb driver

Implementing new fb driver

[Alessio Sangalli]

Hi there, I will be implementing a framebuffer driver for an internally
developed video adapter.

This adapter is able to change resolution and bit depth, has hardware
mouse support and bitblt acceleration. It will be for the ARM9
architecture (AHB bus).

The question is: is there an API to implement to give access to these
features? Which driver you think can be considered similar to take
inspiration from?

Sorry for the stupid questions but I'd like to design a good interface
before beginning to hack... :)

bye
Alessio


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Re: Implementing new fb driver

[krzysztof.h1]

 > Hi there, I will be implementing a framebuffer driver for an internally
 > developed video adapter.
 > 
 > This adapter is able to change resolution and bit depth, has hardware
 > mouse support and bitblt acceleration. It will be for the ARM9
 > architecture (AHB bus).
 > 
 > The question is: is there an API to implement to give access to these
 > features? Which driver you think can be considered similar to take
 > inspiration from?
 > 
 > Sorry for the stupid questions but I\'d like to design a good interface
 > before beginning to hack... :)
 > 
 
There is a driver template called skeletonfb.c. It has extensive comments. Please use it as your template and report any problem (it should be up to date with API but something maybe missing).

A good example of working ARM fb driver is s3c2410fb driver.

Regards,
Krzysztof

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Re: Implementing new fb driver

[Alessio Sangalli]

krzysztof.h1@poczta.fm wrote:

>> Hi there, I will be implementing a framebuffer driver for an
>> internally developed video adapter.

> There is a driver template called skeletonfb.c. It has extensive
> comments. Please use it as your template and report any problem (it
> should be up to date with API but something maybe missing).
> 
> A good example of working ARM fb driver is s3c2410fb driver.


I have a question; this hardware supports (only) true color cursors. Is
the fb API unable to deal with this? I have read only 1-bit cursor
images are supported.

This said, I ma confused by the hw cursors calls, and I am not sure how
to proceed. Basically my hardware can store a number of cursor images,
enable or disable the cursor, and move the cursor at a specified
position. How do I implement that?

Thank you!
Alessio



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Re: Implementing new fb driver

[krzysztof.h1]

> krzysztof.h1@poczta.fm wrote:
> 
> 
> I have a question; this hardware supports (only) true color cursors. Is
> the fb API unable to deal with this? I have read only 1-bit cursor
> images are supported.
> 

No. Look at the include/linux/fb.h

#define FB_CUR_SETIMAGE 0x01
#define FB_CUR_SETPOS   0x02
#define FB_CUR_SETHOT   0x04
#define FB_CUR_SETCMAP  0x08
#define FB_CUR_SETSHAPE 0x10
#define FB_CUR_SETSIZE  0x20
#define FB_CUR_SETALL   0xFF

struct fbcurpos {
    __u16 x, y;
};

struct fb_cursor {
    __u16 set;      /* what to set */
    __u16 enable;       /* cursor on/off */
    __u16 rop;      /* bitop operation */
    const char *mask;   /* cursor mask bits */
    struct fbcurpos hot;    /* cursor hot spot */
    struct fb_image image;  /* Cursor image */
};

You can set colormap for the cursor. 

> This said, I ma confused by the hw cursors calls, and I am not sure how
> to proceed. Basically my hardware can store a number of cursor images,
> enable or disable the cursor, and move the cursor at a specified
> position. How do I implement that?
> 

There is only one function to handle cursor (fb_cursor) which set appropriate properties based on set flags (the constants above). 
One file I fixed cursor handling is the tdfxfb driver (look there).

Best regards,
Krzysztof

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Re: Implementing new fb driver

[Alessio Sangalli]

krzysztof.h1@poczta.fm wrote:

>> the fb API unable to deal with this? I have read only 1-bit cursor
>> images are supported.
>>
> 
> No. Look at the include/linux/fb.h
[...]
> You can set colormap for the cursor. 

Umh... I really have to go and get more details, this part of the driver
is the one I do not really understand well. You mean colormap as in
'palette'? or as in 'bitmap'; this hardware will only support truecolor.

> There is only one function to handle cursor (fb_cursor) which set appropriate properties based on set flags (the constants above). 
> One file I fixed cursor handling is the tdfxfb driver (look there).


I will thank you.

Bye
as


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Re: Implementing new fb driver

[Alessio Sangalli]

Alessio Sangalli wrote:

>>> the fb API unable to deal with this? I have read only 1-bit cursor
>>> images are supported.
>>>
>> No. Look at the include/linux/fb.h


I have another question: in fbmem.h line 1070 function fb_ioctl

        case FBIO_CURSOR:
                return -EINVAL;

is the ioctl 'manager' in this file? Why does it return like this? How
is the userspace supposed to deal with the cursor?

Thank you
Alessio



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Re: Implementing new fb driver

[Krzysztof Helt]

On Thu, 18 Sep 2008 17:15:11 -0700
Alessio Sangalli <alesan@manoweb.com> wrote:

> Alessio Sangalli wrote:
> 
> >>> the fb API unable to deal with this? I have read only 1-bit cursor
> >>> images are supported.
> >>>
> >> No. Look at the include/linux/fb.h
> 
> 
> I have another question: in fbmem.h line 1070 function fb_ioctl
> 
>         case FBIO_CURSOR:
>                 return -EINVAL;
> 
> is the ioctl 'manager' in this file? Why does it return like this? How
> is the userspace supposed to deal with the cursor?
> 

I see. It seems that this ioctl is not implemented. The cursor control works through the console layer but I am not sure if you can set shape through this.

I have no time implement this at the moment.

Regards,
Krzysztof

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Re: Implementing new fb driver

[Alessio Sangalli]

Krzysztof Helt wrote:

> I see. It seems that this ioctl is not implemented. The cursor
> control works through the console layer but I am not sure if you can
> set shape through this.
> 
> I have no time implement this at the moment.

Well, we did implement it, on Monday I will send you a patch to consider.

bye!
as


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