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udlfb: Enable fb_defio by default 

Enables page fault based detection of mmap writes to the framebuffer,
which allows standard fbdev apps (like the generic fbdev xorg driver)
to work on DisplayLink devices.

Not all bugs are shaken out of the fb_defio path of udlfb, but it's
tantalizingly close, so this seems a good time to enable by default.

Alternatively, option can be disabled when running with an xorg driver
that can more directly communicate damaged regions of the framebuffer
via IOCTL. This is a simpler, higher perf option, when available.

Signed-off-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
This commit is contained in:
Bernie Thompson 2011-08-21 13:35:38 -07:00 committed by Florian Tobias Schandinat
parent d3189545ee
commit 9f811b72c6
2 changed files with 18 additions and 10 deletions
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24
Documentation/fb/udlfb.txt
View File

@ -87,20 +87,28 @@ Special configuration for udlfb is usually unnecessary. There are a few
options, however.
From the command line, pass options to modprobe
modprobe udlfb defio=1 console=1
modprobe udlfb fb_defio=0 console=1 shadow=1
Or for permanent option, create file like /etc/modprobe.d/options with text
options udlfb defio=1 console=1
Or modify options on the fly at /sys/module/udlfb/parameters directory via
sudo nano fb_defio
change the parameter in place, and save the file.
Accepted options:
Unplug/replug USB device to apply with new settings
Or for permanent option, create file like /etc/modprobe.d/udlfb.conf with text
options udlfb fb_defio=0 console=1 shadow=1
Accepted boolean options:
fb_defio Make use of the fb_defio (CONFIG_FB_DEFERRED_IO) kernel
module to track changed areas of the framebuffer by page faults.
Standard fbdev applications that use mmap but that do not
report damage, may be able to work with this enabled.
Disabled by default because of overhead and other issues.
Standard fbdev applications that use mmap but that do not
report damage, should be able to work with this enabled.
Disable when running with X server that supports reporting
changed regions via ioctl, as this method is simpler,
more stable, and higher performance.
console Allow fbcon to attach to udlfb provided framebuffers. This
console Allow fbcon to attach to udlfb provided framebuffers. This
is disabled by default because fbcon will aggressively consume
the first framebuffer it finds, which isn't usually what the
user wants in the case of USB displays.

4
drivers/video/udlfb.c
View File

@ -61,7 +61,7 @@ MODULE_DEVICE_TABLE(usb, id_table);
/* module options */
static int console; /* Optionally allow fbcon to consume first framebuffer */
static int fb_defio; /* Optionally enable experimental fb_defio mmap support */
static int fb_defio = 1; /* Detect mmap writes using page faults */
static int shadow = 1; /* Optionally disable shadow framebuffer */
/* dlfb keeps a list of urbs for efficient bulk transfers */
@ -1951,7 +1951,7 @@ module_param(console, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
MODULE_PARM_DESC(console, "Allow fbcon to consume first framebuffer found");
module_param(fb_defio, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
MODULE_PARM_DESC(fb_defio, "Enable fb_defio mmap support. *Experimental*");
MODULE_PARM_DESC(fb_defio, "Page fault detection of mmap writes");
module_param(shadow, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
MODULE_PARM_DESC(shadow, "Shadow vid mem. Disable to save mem but lose perf");