[PATCH] fbdev: Add helper to get an appropriate initial mode

Add new helper, fb_find_best_display(), which will search the modelist for the
best mode for the attached display.  This requires an EDID block that is
converted to struct fb_monspecs and a private modelist.  The search will be
done in this manner:

- if 1st detailed timing is preferred, use that
- else if dimensions of the display are known, use that to estimate xres and
- else if modelist has detailed timings, use the first detailed timing
- else, use the very first entry from the modelist

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 62 insertions, 0 deletions

diff --git a/drivers/video/modedb.c b/drivers/video/modedb.c
index aadef046ce7b..1789a52d776a 100644
--- a/drivers/video/modedb.c
+++ b/drivers/video/modedb.c
@@ -944,6 +944,66 @@ void fb_videomode_to_modelist(struct fb_videomode *modedb, int num,
         }
 }
 
+struct fb_videomode *fb_find_best_display(struct fb_monspecs *specs,
+                                          struct list_head *head)
+{
+        struct list_head *pos;
+        struct fb_modelist *modelist;
+        struct fb_videomode *m, *m1 = NULL, *md = NULL, *best = NULL;
+        int first = 0;
+
+        if (!head->prev || !head->next || list_empty(head))
+                goto finished;
+
+        /* get the first detailed mode and the very first mode */
+        list_for_each(pos, head) {
+                modelist = list_entry(pos, struct fb_modelist, list);
+                m = &modelist->mode;
+
+                if (!first) {
+                        m1 = m;
+                        first = 1;
+                }
+
+                if (m->flag & FB_MODE_IS_FIRST) {
+                        md = m;
+                        break;
+                }
+        }
+
+        /* first detailed timing is preferred */
+        if (specs->misc & FB_MISC_1ST_DETAIL) {
+                best = md;
+                goto finished;
+        }
+
+        /* find best mode based on display width and height */
+        if (specs->max_x && specs->max_y) {
+                struct fb_var_screeninfo var;
+
+                memset(&var, 0, sizeof(struct fb_var_screeninfo));
+                var.xres = (specs->max_x * 7200)/254;
+                var.yres = (specs->max_y * 7200)/254;
+                m = fb_find_best_mode(&var, head);
+                if (m) {
+                        best = m;
+                        goto finished;
+                }
+        }
+
+        /* use first detailed mode */
+        if (md) {
+                best = md;
+                goto finished;
+        }
+
+        /* last resort, use the very first mode */
+        best = m1;
+finished:
+        return best;
+}
+EXPORT_SYMBOL(fb_find_best_display);
+
 EXPORT_SYMBOL(fb_videomode_to_var);
 EXPORT_SYMBOL(fb_var_to_videomode);
 EXPORT_SYMBOL(fb_mode_is_equal);
diff --git a/include/linux/fb.h b/include/linux/fb.h
index 68a787914d85..e7ff98e395f6 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -902,6 +902,8 @@ extern struct fb_videomode *fb_find_nearest_mode(struct fb_videomode *mode,
 extern void fb_destroy_modelist(struct list_head *head);
 extern void fb_videomode_to_modelist(struct fb_videomode *modedb, int num,
                                      struct list_head *head);
+extern struct fb_videomode *fb_find_best_display(struct fb_monspecs *specs,
+                                                 struct list_head *head);
 
 /* drivers/video/fbcmap.c */
 extern int fb_alloc_cmap(struct fb_cmap *cmap, int len, int transp);