[PATCH] udlfb - Fix for problem with monitor resolution detection /

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@alcatel-lucent.com