Improve vt(4) splash screen support

Repository

https://github.com/0mp/freebsd/tree/splash-vt

Bugzilla

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=210432

Overview

At the moment (2018-09-11) vt(4) has very limited support for splash screens.

The goal of this project is to extend it a little bit. It should be possible to:

A stretched goal is to support bitmaps with the color depth of more than 1.

Roadmap

Add sysctl tunables for splash colors in vt(4).

{o}

References

Mailing list threads

Research

Commit adding some splash screen support to vt(4): 2ecca071d5eccf38f9a5fd7a03052b261b7bd7d2

sc(4) supports 8-bit colors.

Interesting functions:

The `vtterm_splash` function

There's a function called vtterm_splash in vt_core.c, which displays a boot splash when the kernel is compiled with DEV_SPLASH option, textmode is not activated and a muted booting was requested by the user (for example via specifying -m to boot(8)).

Also the following part of the vtterm_splash function:

suggests that:

  1. Monochrome colors are the only one supported at the moment.
  2. It should not be complicated to add support for 4-bit and 8-bit colors.
    • Actually, there is an sc(4) file, which has a very similar switch construct handling various color depth configurations.
      • What's the name of the sc(4) function with that switch case?
        • There's no such function in sc(4). There is bmp_SetPix in sys/dev/fb/splash_bmp.c but it does not help much as it directly sets video bits. Its signature looks like this: static void bmp_SetPix(BMP_INFO *info, int x, int y, u_char val).

Other questions regarding the vtterm_splash function:

  1. {o} What is the VDF_SPLASH flag inside vd->vd_flags for?

  2. {o} How to load a BMP file into a structure accepted by functions displaying pixels? Could it be that the splash(4) driver provides all the required functions to do so? Ideal scenario:

    1. The splash(4) driver reads the bitmap file that was specified in loader.conf(5) and converts it to a structure accepted by internal vt(4) functions.
    2. vt(4) gets the structure from splash(4).
    3. vt(4) displays the bitmap.
  3. {o} How does the vd->vd_driver->vd_bitblt_bmp function work?

    • struct vt_driver seems to be an interface for different hardware have to implement in order to use the vt(4) driver. vd_bitblt_bmp happens to be one of the drawing functions. It has various implementations like ofwfb_bitblt_bitmap, vga_bitblt_bitmap or vt_fb_bitblt_bitmap.

At the moment the vt(4) driver stores logos in unsigned char structures (see sys/dev/vt/logo/logo_beastie.c), which roughly correspond to the u_char *data member of the BMP_INFO structure (see sys/dev/fb/splash_bmp.c).

Glossary


CategoryProject

MateuszPiotrowski/ImproveVtSplashScreenSupport (last edited 2018-09-25 07:40:25 by MateuszPiotrowski)