Re: [PATCH] neofb: add more logic to determine sensibility of register readback

[Christian Trefzer <ctrefzer@gmx.de>]

On Fri, Feb 10, 2006 at 11:41:34AM -0500, Kyle Moffett wrote:
> On Feb 10, 2006, at 06:53, Antonino A. Daplas wrote:
> >Christian Trefzer wrote:
> >>+		par->PanelDispCntlRegRead = 0;
> >>+		par->PanelDispCntlRegRead = 0;
> >>+		par->PanelDispCntlRegRead = 0;
> >>+		par->PanelDispCntlRegRead = 0;
> >>+		par->PanelDispCntlRegRead = 1;
> >
> >You can save a few lines by
> >
> >par->PanelDispCntlRegRead = (blank_mode) ? 0 : 1;
> 
> How about the really simple so-obvious-its-impossible-to-misread  
> solution?
> 
> par->PanelDispCntlRegRead = !blank_mode;

Where is my mind..?

Sure, why not. Guess I had my head too much in the smoke clouds of not
knowing why a dead-sure-to-work implementation still would not do the
right thing, I already thought I got the C representation of true and
false wrong. Even Tony's hint would be clearer than my code, but that
can in turn be condensed into something really obvious. It's just a
negation, after all. Silly me.

Changed patch below. Should be the final one now, right?

Signed-off-by: Christian Trefzer <ctrefzer@gmx.de>


--- a/include/video/neomagic.h	2006-01-03 04:21:10.000000000 +0100
+++ b/include/video/neomagic.h	2006-02-09 20:59:20.164839408 +0100
@@ -159,6 +159,7 @@
 	unsigned char PanelDispCntlReg1;
 	unsigned char PanelDispCntlReg2;
 	unsigned char PanelDispCntlReg3;
+	unsigned char PanelDispCntlRegRead;
 	unsigned char PanelVertCenterReg1;
 	unsigned char PanelVertCenterReg2;
 	unsigned char PanelVertCenterReg3;
--- a/drivers/video/neofb.c	2006-02-08 21:24:05.000000000 +0100
+++ b/drivers/video/neofb.c	2006-02-11 11:39:39.346365480 +0100
@@ -843,6 +843,9 @@
 
 	par->SysIfaceCntl2 = 0xc0;	/* VESA Bios sets this to 0x80! */
 
+	/* Initialize: by default, we want display config register to be read */
+	par->PanelDispCntlRegRead = 1;
+
 	/* Enable any user specified display devices. */
 	par->PanelDispCntlReg1 = 0x00;
 	if (par->internal_display)
@@ -1334,8 +1337,12 @@
 	struct neofb_par *par = (struct neofb_par *)info->par;
 	int seqflags, lcdflags, dpmsflags, reg;
 
-	/* Reload the value stored in the register, might have been changed via FN keystroke */
-	par->PanelDispCntlReg1 = vga_rgfx(NULL, 0x20) & 0x03;
+	/* Reload the value stored in the register, if sensible. It might have been
+	 * changed via FN keystroke. */
+	if (par->PanelDispCntlRegRead && !blank_mode) {
+		par->PanelDispCntlReg1 = vga_rgfx(NULL, 0x20) & 0x03;
+	}
+	par->PanelDispCntlRegRead = !blank_mode;
 	
 	switch (blank_mode) {
 	case FB_BLANK_POWERDOWN:	/* powerdown - both sync lines down */

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