Hello,
This is my first contribution on this list, so please let me know if I am off with any procedures or anything.
This patch fixes a problem where a DisplayLink device autoselects a suboptimal framebuffer resolution. The problem occured with a Plugable UGA-2K-A connected to a Samsung EX2220X display. In this situation, the driver always allocates a 1600x1200 framebuffer, even after it indicates in its output that 1920x1080 is a valid mode. If my interpretation of the code is correct, the problem was in the block that selects the best mode. The existing code unset the FB_MISC_1ST_DETAIL flag if ANY of the modes is determined to be invalid (on my adapter, 1680x1680 is invalid). This in turn causes the fb_find_best_display() function to disregard the first mode (1920x1080). The comment for the line that unsets the flag implies that this should happen if we have removed the top/best mode...however, this else block is not qualified, and happens if we remove any mode. I simply put in a condition so that we only unset this flag if the first mode is invalid.
Thanks in advance for your feedback.
Bill Katsak
Bell Laboratories
Alcatel-Lucent, Inc.
william.katsak@xxxxxxxxxxxxxxxxxx
From c3327c41877637e80f9f06a8ce3bdcfe8b4e6fa4 Mon Sep 17 00:00:00 2001
From: William Katsak <william.katsak@xxxxxxxxxxxxxxxxxx>
Date: Wed, 22 Jun 2011 12:48:11 -0400
Subject: [PATCH] This patch fixes a problem where a DisplayLink device autoselects a
suboptimal framebuffer resolution.
The situation in which the problem occurred was with a Plugable UGA-2K-A
connected to a Samsung EX2220X display. The driver indicates that
1920x1080 is a valid mode (the first mode available, in fact), but
proceeds to set the framebuffer size to 1600x1200.
The patch corrects what seems to be a logic error, regarding unsetting
the FB_MISC_1ST_DETAIL flag, if the first (top/best) mode is invalid.
The existing code unset the flag if ANY mode was invalid.
---
drivers/video/udlfb.c | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/video/udlfb.c b/drivers/video/udlfb.c
index 52b0f3e..816a4fd 100644
--- a/drivers/video/udlfb.c
+++ b/drivers/video/udlfb.c
@@ -1233,8 +1233,12 @@ static int dlfb_setup_modes(struct dlfb_data *dev,
if (dlfb_is_valid_mode(&info->monspecs.modedb[i], info))
fb_add_videomode(&info->monspecs.modedb[i],
&info->modelist);
- else /* if we've removed top/best mode */
- info->monspecs.misc &= ~FB_MISC_1ST_DETAIL;
+ else {
+ if (i == 0)
+ /* if we've removed top/best mode */
+ info->monspecs.misc
+ &= ~FB_MISC_1ST_DETAIL;
+ }
}
default_vmode = fb_find_best_display(&info->monspecs,
--
1.7.3.4
