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| author | Stuart Hopkins <stuart@linux-depot.com> | 2011-08-21 13:34:17 -0700 |
|---|---|---|
| committer | Florian Tobias Schandinat <FlorianSchandinat@gmx.de> | 2011-08-24 10:10:44 +0000 |
| commit | d3189545ee69527e949769b89a4cbb331de97b4a (patch) | |
| tree | 170eff40bdf5c47cc4c35c13f1c927a952f32783 /Documentation/fb/udlfb.txt | |
| parent | def76608681983c1fe70c0fa780d8fe777442ef5 (diff) | |
| download | lwn-d3189545ee69527e949769b89a4cbb331de97b4a.tar.gz lwn-d3189545ee69527e949769b89a4cbb331de97b4a.zip | |
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 <stuart@linux-depot.com>
Signed-off-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Diffstat (limited to 'Documentation/fb/udlfb.txt')
| -rw-r--r-- | Documentation/fb/udlfb.txt | 5 |
1 files changed, 5 insertions, 0 deletions
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 ================ |