From d3189545ee69527e949769b89a4cbb331de97b4a Mon Sep 17 00:00:00 2001 From: Stuart Hopkins Date: Sun, 21 Aug 2011 13:34:17 -0700 Subject: udlfb: Add module option to do without shadow framebuffer By default, udlfb allocates a 2nd buffer to shadow what's across the bus on the USB device. It can operate without this shadow, but then it cannot tell which pixels have changed, and must send all. Saves host memory, but worsens the USB 2.0 bus bottleneck. This option allows users in very low memory situations (e.g. bifferboard) to optionally turn off this shadow framebuffer. Signed-off-by: Stuart Hopkins Signed-off-by: Bernie Thompson Signed-off-by: Florian Tobias Schandinat --- Documentation/fb/udlfb.txt | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'Documentation/fb') diff --git a/Documentation/fb/udlfb.txt b/Documentation/fb/udlfb.txt index 7fdde2a02a27..473ceed9e4eb 100644 --- a/Documentation/fb/udlfb.txt +++ b/Documentation/fb/udlfb.txt @@ -105,6 +105,11 @@ console Allow fbcon to attach to udlfb provided framebuffers. This the first framebuffer it finds, which isn't usually what the user wants in the case of USB displays. +shadow Allocate a 2nd framebuffer to shadow what's currently across + the USB bus in device memory. If any pixels are unchanged, + do not transmit. Spends host memory to save USB transfers. + Enabled by default. Only disable on very low memory systems. + Sysfs Attributes ================ -- cgit v1.2.3-55-g7522