[PATCH 1/4] fbdev: make fb_find_mode look for a mode with the highest refresh rate

[PATCH 1/4] fbdev: make fb_find_mode look for a mode with the highest refresh rate

[Michal Januszewski]

If the refresh rate hasn't been explicitly specified, fd_find_mode
currently returns the first mode with the requested resolution. Change
it so that it returns a mode with the requested resolution and the
highest refresh rate.

Also export fb_destroy_modelist, which is used in uvesafb.

Signed-off-by: Michal Januszewski <spock@gentoo.org>
---
drivers/video/modedb.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/video/modedb.c b/drivers/video/modedb.c
index 3741ad7..98ee77b 100644
--- a/drivers/video/modedb.c
+++ b/drivers/video/modedb.c
@@ -606,16 +606,18 @@ done:
 	DPRINTK("Trying specified video mode%s %ix%i\n",
 	    refresh_specified ? "" : " (ignoring refresh rate)", xres, yres);
 
+	if (!refresh_specified)
+		refresh = 200;
 	diff = refresh;
 	best = -1;
 	for (i = 0; i < dbsize; i++) {
 		if (name_matches(db[i], name, namelen) ||
 		    (res_specified && res_matches(db[i], xres, yres))) {
 			if(!fb_try_mode(var, info, &db[i], bpp)) {
-				if(!refresh_specified || db[i].refresh == refresh)
+				if (refresh_specified && db[i].refresh == refresh)
 					return 1;
 				else {
-					if(diff > abs(db[i].refresh - refresh)) {
+					if (diff > abs(db[i].refresh - refresh)) {
 						diff = abs(db[i].refresh - refresh);
 						best = i;
 					}
@@ -938,6 +940,7 @@ void fb_destroy_modelist(struct list_head *head)
 		kfree(pos);
 	}
 }
+EXPORT_SYMBOL_GPL(fb_destroy_modelist);
 
 /**
  * fb_videomode_to_modelist: convert mode array to mode list

Re: [PATCH 1/4] fbdev: make fb_find_mode look for a mode with the highest refresh rate

[Andrew Morton]

On Sat, 23 Jun 2007 12:50:46 +0200 Michal Januszewski <spock@gentoo.org> wrote:

> If the refresh rate hasn't been explicitly specified, fd_find_mode
> currently returns the first mode with the requested resolution. Change
> it so that it returns a mode with the requested resolution and the
> highest refresh rate.
> 
> Also export fb_destroy_modelist, which is used in uvesafb.
> 
> Signed-off-by: Michal Januszewski <spock@gentoo.org>
> ---
> drivers/video/modedb.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/modedb.c b/drivers/video/modedb.c
> index 3741ad7..98ee77b 100644
> --- a/drivers/video/modedb.c
> +++ b/drivers/video/modedb.c
> @@ -606,16 +606,18 @@ done:
>  	DPRINTK("Trying specified video mode%s %ix%i\n",
>  	    refresh_specified ? "" : " (ignoring refresh rate)", xres, yres);
>  
> +	if (!refresh_specified)
> +		refresh = 200;
>  	diff = refresh;
>  	best = -1;
>  	for (i = 0; i < dbsize; i++) {
>  		if (name_matches(db[i], name, namelen) ||
>  		    (res_specified && res_matches(db[i], xres, yres))) {
>  			if(!fb_try_mode(var, info, &db[i], bpp)) {
> -				if(!refresh_specified || db[i].refresh == refresh)
> +				if (refresh_specified && db[i].refresh == refresh)
>  					return 1;
>  				else {
> -					if(diff > abs(db[i].refresh - refresh)) {
> +					if (diff > abs(db[i].refresh - refresh)) {
>  						diff = abs(db[i].refresh - refresh);
>  						best = i;
>  					}
> @@ -938,6 +940,7 @@ void fb_destroy_modelist(struct list_head *head)
>  		kfree(pos);
>  	}
>  }
> +EXPORT_SYMBOL_GPL(fb_destroy_modelist);
>  

fbdev ignoramus asks: isn't this pretty risky?  People who were previously
relying upon (or at least using) the kernel's default resolution will find
their displays coming up in a quite different resolution.

This change seems to be quite unrelated to the uvesafb stuff and should be
in a separate patch from the export, which _is_ uvesafb-related.  I think. 
If that's wrong then the changelog could do with some attention.

Re: [PATCH 1/4] fbdev: make fb_find_mode look for a mode with the highest refresh rate

[Michal Januszewski]

On Sat, Jun 23, 2007 at 11:04:24AM -0700, Andrew Morton wrote:
> On Sat, 23 Jun 2007 12:50:46 +0200 Michal Januszewski <spock@gentoo.org> wrote:
> 
> > +	if (!refresh_specified)
> > +		refresh = 200;
> >  	diff = refresh;
> >  	best = -1;
> >  	for (i = 0; i < dbsize; i++) {
> >  		if (name_matches(db[i], name, namelen) ||
> >  		    (res_specified && res_matches(db[i], xres, yres))) {
> >  			if(!fb_try_mode(var, info, &db[i], bpp)) {
> > -				if(!refresh_specified || db[i].refresh == refresh)
> > +				if (refresh_specified && db[i].refresh == refresh)
> >  					return 1;
> >  				else {
> > -					if(diff > abs(db[i].refresh - refresh)) {
> > +					if (diff > abs(db[i].refresh - refresh)) {
> >  						diff = abs(db[i].refresh - refresh);
> >  						best = i;
> >  					}
> > @@ -938,6 +940,7 @@ void fb_destroy_modelist(struct list_head *head)
> >  		kfree(pos);
> >  	}
> >  }
> > +EXPORT_SYMBOL_GPL(fb_destroy_modelist);
> >  
> 
> fbdev ignoramus asks: isn't this pretty risky?  People who were previously
> relying upon (or at least using) the kernel's default resolution will find
> their displays coming up in a quite different resolution.

The resolution will be unchanged (this part of the code is only executed
if either the name of the mode or the resolution are a match).

What can change is the refresh rate -- it can be set higher than what it
used to be before.  But since we're checking all modes with fb_try_mode(),
(which calls fb_check_var()), I think that this change should be safe.
 
To avoid any side effects we could also do the following:

	for (i = 0; i < dbsize; i++) {
		if (name_matches(db[i], name, namelen) ||
		    (res_specified && res_matches(db[i], xres, yres))) {
			if(!fb_try_mode(var, info, &db[i], bpp)) {
				if (refresh_specified && db[i].refresh == refresh)
					return 1;
				else {
					if (diff > abs(db[i].refresh - refresh)) {
						diff = abs(db[i].refresh - refresh);
						best = i;
					}
				}
			}
		}
	}

	if (best != -1) {
		fb_try_mode(var, info, &db[best], bpp);
-		return 2;
+ 		return (refresh_specified) ? 2 : 1;
	}

which would ensure that 1 is returned if the refresh rate is not
explicitly specified, just as it is done currently:

				if(!refresh_specified || db[i].refresh == refresh)
					return 1

I might be missing something here, so it would be nice if someone
involved in the fb development could comment on the proposed change.

> This change seems to be quite unrelated to the uvesafb stuff and should be
> in a separate patch from the export, which _is_ uvesafb-related.  I think. 
> If that's wrong then the changelog could do with some attention.

You're right, I'll split this into two patches in the next round.

Best regards,
Michal

Re: [Linux-fbdev-devel] [PATCH 1/4] fbdev: make fb_find_mode look for a mode with the highest refresh rate

[Antonino A. Daplas]

On Sat, 2007-06-23 at 12:50 +0200, Michal Januszewski wrote:
> If the refresh rate hasn't been explicitly specified, fd_find_mode
> currently returns the first mode with the requested resolution. Change
> it so that it returns a mode with the requested resolution and the
> highest refresh rate.
> 
> Also export fb_destroy_modelist, which is used in uvesafb.
> 
> Signed-off-by: Michal Januszewski <spock@gentoo.org>
> ---
> drivers/video/modedb.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/modedb.c b/drivers/video/modedb.c
> index 3741ad7..98ee77b 100644
> --- a/drivers/video/modedb.c
> +++ b/drivers/video/modedb.c
> @@ -606,16 +606,18 @@ done:
>  	DPRINTK("Trying specified video mode%s %ix%i\n",
>  	    refresh_specified ? "" : " (ignoring refresh rate)", xres, yres);
>  
> +	if (!refresh_specified)
> +		refresh = 200;
>  	diff = refresh;

How about..?

	if (!refresh_specified)
		diff = 0;
	else
		diff = refresh;

>  	best = -1;
>  	for (i = 0; i < dbsize; i++) {
>  		if (name_matches(db[i], name, namelen) ||
>  		    (res_specified && res_matches(db[i], xres, yres))) {
>  			if(!fb_try_mode(var, info, &db[i], bpp)) {
> -				if(!refresh_specified || db[i].refresh == refresh)
> +				if (refresh_specified && db[i].refresh == refresh)
>  					return 1;
>  				else {
> -					if(diff > abs(db[i].refresh - refresh)) {
> +					if (diff > abs(db[i].refresh - refresh)) {
>  						diff = abs(db[i].refresh - refresh);
>  						best = i;
>  					}
then
					if (diff < db[i].refresh) {
						diff = db[i].refresh;
						best = i;
					}

Tony

Re: [Linux-fbdev-devel] [PATCH 1/4] fbdev: make fb_find_mode look for a mode with the highest refresh rate

[Antonino A. Daplas]

On Sat, 2007-06-23 at 11:04 -0700, Andrew Morton wrote:
> On Sat, 23 Jun 2007 12:50:46 +0200 Michal Januszewski <spock@gentoo.org> wrote:
> 
> > If the refresh rate hasn't been explicitly specified, fd_find_mode
> > currently returns the first mode with the requested resolution. Change
> > it so that it returns a mode with the requested resolution and the
> > highest refresh rate.
> > 
> > Also export fb_destroy_modelist, which is used in uvesafb.
> > 
> > Signed-off-by: Michal Januszewski <spock@gentoo.org>
> > ---
> > drivers/video/modedb.c |    7 +++++--
> >  1 files changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/video/modedb.c b/drivers/video/modedb.c
> > index 3741ad7..98ee77b 100644
> > --- a/drivers/video/modedb.c
> > +++ b/drivers/video/modedb.c
> > @@ -606,16 +606,18 @@ done:
> >  	DPRINTK("Trying specified video mode%s %ix%i\n",
> >  	    refresh_specified ? "" : " (ignoring refresh rate)", xres, yres);
> >  
> > +	if (!refresh_specified)
> > +		refresh = 200;
> >  	diff = refresh;
> >  	best = -1;
> >  	for (i = 0; i < dbsize; i++) {
> >  		if (name_matches(db[i], name, namelen) ||
> >  		    (res_specified && res_matches(db[i], xres, yres))) {
> >  			if(!fb_try_mode(var, info, &db[i], bpp)) {
> > -				if(!refresh_specified || db[i].refresh == refresh)
> > +				if (refresh_specified && db[i].refresh == refresh)
> >  					return 1;
> >  				else {
> > -					if(diff > abs(db[i].refresh - refresh)) {
> > +					if (diff > abs(db[i].refresh - refresh)) {
> >  						diff = abs(db[i].refresh - refresh);
> >  						best = i;
> >  					}
> > @@ -938,6 +940,7 @@ void fb_destroy_modelist(struct list_head *head)
> >  		kfree(pos);
> >  	}
> >  }
> > +EXPORT_SYMBOL_GPL(fb_destroy_modelist);
> >  
> 
> fbdev ignoramus asks: isn't this pretty risky?  People who were previously
> relying upon (or at least using) the kernel's default resolution will find
> their displays coming up in a quite different resolution.

It's only the refresh rate that will change.  The current behavior is
that a user can get near random results in terms of the vertical refresh
rates.  At least with this patch, we know what we get.

> 
> This change seems to be quite unrelated to the uvesafb stuff and should be
> in a separate patch from the export, which _is_ uvesafb-related.  I think. 
> If that's wrong then the changelog could do with some attention.
> 

Tony