Messages in this thread | | | Subject | Re: [Linux-fbdev-devel] [PATCH] FBDev: vga16fb port | From | Antonino Daplas <> | Date | 05 Dec 2002 06:04:52 +0500 |
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On Wed, 2002-12-04 at 21:47, Sven Luther wrote: > > > So there is no common zqy of doing this, my docs say something about a > > > vga control register zhich is accesses trough the sequencer regs. Does > > > vgafb (or textmode or whatever) not call this when giving the hand to > > > the fbdev ? > > No, when a video card goes to graphics mode, it's up to the driver to > > program the registers. vgacon/vga16fb only touches the standard VGA > > So we will have a repeat of the exact same code snipplet in all the > drivers ? I thought the new API was about having all the common code in > common and not duplicated in all the drivers. Could we have at least a > gen_disable_vga function or something such that we could call ?
Not exactly. Different hardware programs those registers differently. Ie, vga will probably program the crtc regs for 640x400@60. Your hardware can probably do better than that. So the code cannot be shared. However, saving and restoring the standard VGA regs can be common.
> > > registers (crtc[25], attr[21], seq[5], gfx[9], misc[1]). Usage is pretty > > Well, i need to disable the vga output in seq[5], more exactly bit 3 > called "enable VGA display", need to be reset. > [...] > > Err, it is seq[5], called VGAControlRegister, so it is beyond the > standard seq registers (seq[0] to seq[5]), right ?
I meant seq[0] to seq[4] are standard VGA regs. So seq[5] is extended. It's VGAControlRegister in your hardware, it's not used in mine.
> [...] > > > Mmm, what about interaction with X ? X also does a save/restore of the > > > previous (text) mode, when a X driver is _not_ fbdev aware, it will > > > save/restore the things twice, right ? > > > > > Not twice just the current mode it was in when X launched, although it > > always assumes text mode. Same thing for fbdev, it should only restore > > Well, but fbdev will save its state and X will save it again, so the > saving done in the X driver is not all that important, and i could > ignore it at first if i already have an fbdev.
If X is running in native mode then it has to save the register state. Otherwise you cannot switch to a console. If X is running on top of fbdev, then state restore/saves are done using fb_set_var and fb_get_var. The registers are not touched, that's the purpose of fbdev.
If you are running vgacon, fbdev, and native X, then yes, fbdev and X has to do a save of their initial state.
> > Does this also apply to vesafb ? Not too sure about this. vesa requires real-mode initialization. Either you do this at boot time, or fake a real-mode environment like what X does.
> > > the state when reference count becomes zero. If the framebuffer console > > is loaded, the reference count will never be zero unless it is > > unloaded. If the framebuffer console is not loaded, the only time you > > will save and restore the state is when some fb-based application > > attempts to open/close /dev/fbx. > > Ok, ... > [...]
Tony
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