* Re: Framebuffer Port guide for 2.4->2.6?
2004-11-03 19:11 Framebuffer Port guide for 2.4->2.6? Kelly Price
@ 2004-11-04 1:46 ` Antonino A. Daplas
2004-11-08 13:33 ` Dermot Bradley
1 sibling, 0 replies; 3+ messages in thread
From: Antonino A. Daplas @ 2004-11-04 1:46 UTC (permalink / raw)
To: linux-fbdev-devel, Kelly Price
On Thursday 04 November 2004 03:11, Kelly Price wrote:
> Is there a port guide for framebuffer drivers going from 2.4 to 2.6?
> I'm trying to port the CT65548 Frambuffer driver over to 2.6.
>
> http://members.elysium.pl/ytm/html/linux.html is where the 2.4 version
> is at.
>
>
Can you just add the chip support to the chipsfb driver which currently
supports CT 65550, or are the chipsets too different that they deserve
different drivers?
Anyway there are a scarcity of documentation about the framebuffer system,
especially in 2.6. So here's a start:
In general, you need to allocate:
struct fb_info - structure that acts as a glue between the console, userspace
and driver
void *fb_info.par = xxxfb_par - struct that is private to the driver:
The above are the only data that the driver needs to access in order to
function correctly.
Your xxxfb_init() function must be module_init(). No need to alter other
files except the Makefile and Kconfig.
In general start your xxxfb_init() function with this:
if (fb_get_options("chipsfb", NULL))
return -ENODEV
Or if the driver needs to parse options with xxxfb_setup(), then
char *option = NULL;
if (fb_get_options("chipsfb", &option))
return -ENODEV;
xxxfb_setup(option);
int __init xxxfb_init(void) {
struct xxxfb_par *par;
struct fb_info *info;
... call fb_get_options() here;
... allocate the driver structures
info = framebuffer_alloc(sizeof(struct xxxfb_par));
... check for errors
par = info->par;
... do your stuff here, allocation of resources, etc;
xxx
... then fill up the fb_info structure, very important:
info->fbops = xxxfb_ops;
info->var = xxxfb_var; /* the mode the driver will boot into */
info->fix = xxxfb_fix; /* the fix struct the driver will boot into */
info->screen_base = xxx; /* the virtual address of the framebuffer */
fb_alloc_cmap(&info->cmap, 256, 0); /* 256 is a generally safe value*/
info->flags = FBINFO_DEFAULT | other options; /* not very important */
... finally register the framebuffer
register_framebuffer(info);
... and exit
return 0;
}
struct fb_ops xxxfb_ops;
1. In 2.4, the drawing function are in struct display->dispsw = fbcon_cfb* or
ct48b_accel. This is gone now, instead, the following hooks in struct fb_ops
are used instead:
fb_imageblit (required)
fb_copyarea (required)
fb_fillrect (required)
fb_cursor (required)
The generic versions are:
cfb_imageblit - used by the putc, putcs methods and logo drawing
cfb_copyarea - used by the bmove method
cfb_fillrect - used by the clear, clear_margins methods
soft_cursor - the cursor method
They will work correctly as long as the driver is in packed-pixel mode at
whatever bpp. soft_cursor will always work.
Test your driver with the generic functions, then you can write your own
hardware implementation.
2. The 2.4 version set_var is split into 2:
fb_check_var (optional);
fb_set_par (optional);
2.a In fb_check_var, the driver will be passed with a var structure and all
the driver needs to do is check the contents and can do the following:
a. alter the contents of the var to fit the hardware capability
b. return -EINVAL if any of the fields in var does not fit the hardware
The first is the preferred response.
2.b In fb_set_par, the driver will actually modify the hardware according to
the contents of info->var _only_. This is important.
3. fb_setcolreg (optional)
Not very different from the 2.4 version except that info->pseudo_palette
needs to be filled up if in directcolor or truecolor mode. Also, if using
the generic cfb_* drawing functions, the pseudo_palette is always (u32 *).
The pseudo_palette must be a minimum of 16 entries. The pseudo_palette is
the same as 2.4' s display->dispsw_data.
4. fb_pan_display(optional)
optional function, not too different from the 2.4 version.
5. fb_sync (optional unless the driver has hardware accelerated drawing)
wait for engine idle (blit idle usually)
6. fb_blank, fb_ioctl, fb_mmap are optional.
Note that the get_fix, get_var, set_var, getcolreg hooks in 2.4 are
gone in 2.6.
If you have further questions, just write to this list.
Tony
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