DisplayLink on Fedora Linux

I had the opportunity to recently try one of the DisplayLink’s USB 2.0 graphics adapter. This one is supposedly a DL-165 but was bought on eBay as a “USB 2.0 to VGA DVI HDMI Multi-Display Graphic Adapter” for about 35EUR. Its purpose will be the projection of presentations and other e-learning materials in a school by a teacher. It’s a USB to DVI graphics adapter which comes with 2 adapters:

• 1 x DVI to VGA
• 1 x DVI to HDMI

     

Linux says it’s a DisplayLink SUNWEIT USB Display Adapter see bellow:

[  122.227846] usb 2-1.3: New USB device found, idVendor=17e9, idProduct=024c
[  122.227853] usb 2-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[  122.227858] usb 2-1.3: Product: SUNWEIT USB Display
[  122.227862] usb 2-1.3: Manufacturer: DisplayLink
[  122.227866] usb 2-1.3: SerialNumber: 00000000-000794

I had several problems to put this to work under Linux as you will see next. I’ve googled around to look for setup instructions and found that starting from kernel 2.6.38 the udlfb driver which drives diplaylink devices under linux has been moved from staging to main kernel tree.
However the latest udlfb driver can also be obtained from here and the latest displaylink X.org driver can be pulled from here.

Now the setup procedure:

1. I’ve decided to recompile kernel 3.0.4 in order to include udlfb (see my previous post on how to compile your custom vanilla kernel if you need directions here).
2. I’ve found out somewhere, maybe here that after udlfb driver is correctly installed in your system you should get a green display, so after recompiling kernel 3.0.4 to include udlfb driver i’ve plugged the usb cable and have immediately gotten my green display as seen bellow.



3. When you get your green screen you will also find a new device under /dev/fb1 see dmesg log bellow

   [ 9937.250452] udlfb: DisplayLink USB device /dev/fb1 attached. 800x600 resolution. Using 1880K framebuffer memory
   [ 9937.250501] usbcore: registered new interface driver udlfb
   

4. The next step should be compiling the displaylink X.org driver. Start by cloning xf-video-udlfb git repo:

   git clone http://git.plugable.com/webdav/xf-video-udlfb
   cd xf-video-udlfb
   ./configure
   make && make install

   When done you will have two new files under /usr/local/lib/xorg/modules/drivers/

   [root@dell udlfb]# ls -l /usr/local/lib/xorg/modules/drivers/
   total 160
   -rwxr-xr-x 1 root root    993 Sep 19 00:56 displaylink_drv.la
   -rwxr-xr-x 1 root root 157291 Sep 19 00:56 displaylink_drv.so
   

5. link displaylink_drv.so to /usr/lib64/xorg/modules/drivers/ if under x86_64 arch or /usr/lib/xorg/modules/drivers/ if i386 arch.

   ln -s /usr/local/lib/xorg/modules/drivers/displaylink_drv.so /usr/lib64/xorg/modules/drivers/

   or

   ln -s /usr/local/lib/xorg/modules/drivers/displaylink_drv.so /usr/lib/xorg/modules/drivers/

   You are done for now.

6. Now it’s time to tailor a custom xorg.conf file for use. Recent Linux distros don’t come with a /etc/X11/xorg.conf file anymore so to generate a starting point issue the following command:

   X -configure

   you will maybe need to change to runlevel 3 to run the previous command successfully, you can do that by running init 3 as root.
   This command will create a xorg.conf.new as a basic starting point. Start by editing it to feet your needs. Remember that the displaylink monitor needs to be primary starting at:

   X.pos 0
   Y.pos 0

   take a look into xorg.conf manual

   man xorg.conf

   to learn more about xorg.conf’s options. You can also look at xf-video-udlfb README file you got previously.
   Bellow you can see how my xorg.conf file become after some tailoring:

   Section "ServerLayout"
   	Identifier     "X.org Configured"
   	Screen      0  "Screen1" 0 0
   	Screen      1  "Screen0" 1024 0
   	InputDevice    "Mouse0" "CorePointer"
   	InputDevice    "Keyboard0" "CoreKeyboard"
   	Option		"Xinerama" "On"
   EndSection
   
   Section "Extensions"
       Option "Composite" "Enable"
   EndSection
   
   Section "Files"
   	ModulePath   "/usr/lib64/xorg/modules"
   	FontPath     "catalogue:/etc/X11/fontpath.d"
   	FontPath     "built-ins"
   EndSection
   
   Section "InputDevice"
   	Identifier  "Keyboard0"
   	Driver      "kbd"
   EndSection
   
   Section "InputDevice"
   	Identifier  "Mouse0"
   	Driver      "mouse"
   	Option	    "Protocol" "auto"
   	Option	    "Device" "/dev/input/mice"
   	Option	    "ZAxisMapping" "4 5 6 7"
   EndSection
   
   Section "Monitor"
   	Identifier   "Monitor0"
   	Option	     "Primary" "true"
   EndSection
   
   Section "Monitor"
   	#DisplaySize 304 228 # mm
   	Identifier "Monitor1"
   	VendorName "SNY"
   	ModelName "SDM-HS53"
   	Option "DPMS"
   	# 1024x768 @ 75.10 Hz (GTF) hsync: 60.23 kHz; pclk: 81.91 MHz
   	Modeline "1024x768_75.10"  81.91  1024 1080 1192 1360  768 769 772 802  -HSync +Vsync
   	Option	     "Primary" "false"
   EndSection
   
   Section "Device"
   	Identifier  "Card0"
   	Driver      "intel"
   	BusID       "PCI:0:2:0"
   EndSection
   
   Section "Device"
   	Identifier  "Card1"
   	Driver      "displaylink"
   	Option "fbdev" "/dev/fb1"
   EndSection
   
   Section "Screen"
   	Identifier "Screen0"
   	Device     "Card0"
   	Monitor    "Monitor0"
   	DefaultDepth 16
   	SubSection "Display"
   		Depth     1
   		Modes     "1440x900"
   	EndSubSection
   	SubSection "Display"
   		Depth     4
   		Modes     "1440x900"
   	EndSubSection
   	SubSection "Display"
   		Depth     8
   		Modes     "1440x900"
   	EndSubSection
   	SubSection "Display"
   		Depth     15
   		Modes     "1440x900"
   	EndSubSection
   	SubSection "Display"
   		Depth     16
   		Modes     "1440x900"
   	EndSubSection
   	SubSection "Display"
   		Depth     24
   		Modes     "1440x900"
   	EndSubSection
   EndSection
   
   Section "Screen"
   	Identifier "Screen1"
   	Device     "Card1"
   	Monitor    "Monitor1"
   	DefaultDepth 16
   	SubSection "Display"
   		Depth     1
   		Modes	  "1024x768_75.10" "1024x768"
   	EndSubSection
   	SubSection "Display"
   		Depth     4
   		Modes	  "1024x768_75.10" "1024x768"
   	EndSubSection
   	SubSection "Display"
   		Depth     8
   		Modes	  "1024x768_75.10" "1024x768"
   	EndSubSection
   	SubSection "Display"
   		Depth     15
   		Modes	  "1024x768_75.10" "1024x768"
   	EndSubSection
   	SubSection "Display"
   		Depth     16
   		Modes	  "1024x768_75.10" "1024x768"
   	EndSubSection
   	SubSection "Display"
   		Depth     24
   		Modes	  "1024x768_75.10" "1024x768"
   	EndSubSection
   EndSection
   

   gtf command can also become handy here

   man gtf

7. Finally let’s test our setup:
   To do that lets create a new X session, issue the following:

   startx -- :2 -config xorg.conf.new

   If everything went OK you should be now seeing an extended desktop on a new X session with the displaylink monitor set as primary.
   If for some reason this didn’t workout for you, don’t worry you have probably run into some of the issues i have too ;-).
   The rest of this blog post will introduce you to some problems I’ve found and how you can workaround those if you also run into them. You will want to look at /var/log/Xorg.*.log and dmesg logs from time to time to try to understand what’s going on.

Lets now start some debugging

1. In my case after running

   startx -- :2 -config xorg.conf.new

   i got a segmentation fault WTF? right?
   my log file stated the following

   [   265.190] (--) using VT number 8
   
   [   267.692] (WW) Falling back to old probe method for displaylink
   [   267.692] (II) Loading sub module "fbdevhw"
   [   267.692] (II) LoadModule: "fbdevhw"
   [   267.692] (II) Loading /usr/lib64/xorg/modules/libfbdevhw.so
   [   267.692] (II) Module fbdevhw: vendor="X.Org Foundation"
   [   267.692]    compiled for 1.9.5, module version = 0.0.2
   [   267.692]    ABI class: X.Org Video Driver, version 8.0
   [   267.692] (II) DL(0): using /dev/fb1
   [   267.692] (EE) DL(0): Unknown EDID version 0
   [   267.692] (**) DL(0): Depth 16, (--) framebuffer bpp 16
   [   267.692] (==) DL(0): RGB weight 565
   [   267.692] (==) DL(0): Default visual is TrueColor
   [   267.692] (==) DL(0): Using gamma correction (1.0, 1.0, 1.0)
   [   267.692] (II) DL(0): hardware: udlfb (video memory: 940kB)
   [   267.692] (**) DL(0): Option "fbdev" "/dev/fb1"
   [   267.692] (II) Loading sub module "fb"
   [   267.692] (II) LoadModule: "fb"
   [   267.693] (II) Loading /usr/lib64/xorg/modules/libfb.so
   [   267.693] (II) Module fb: vendor="X.Org Foundation"
   [   267.693]    compiled for 1.9.5, module version = 1.0.0
   [   267.693]    ABI class: X.Org ANSI C Emulation, version 0.4
   [   267.693] (II) DL(0): Output udlfb using monitor section Monitor1
   [   267.693] (**) DL(0): Option "Primary" "false"
   [   267.693] (EE) DL(0): Unknown EDID version 245
   [   267.693] (II) DL(0): EDID for output udlfb
   [   267.693]
   Backtrace:
   [   267.693] 0: /usr/bin/X (xorg_backtrace+0x28) [0x4a0908]
   [   267.694] 1: /usr/bin/X (0x400000+0x60e99) [0x460e99]
   [   267.694] 2: /lib64/libc.so.6 (0x355e200000+0x33140) [0x355e233140]
   [   267.694] 3: /usr/lib64/xorg/modules/drivers/displaylink_drv.so (0x7ff1425d0000+0x382e) [0x7ff1425d382e]
   [   267.694] 4: /usr/bin/X (InitOutput+0x802) [0x470bb2]
   [   267.694] 5: /usr/bin/X (0x400000+0x213cd) [0x4213cd]
   [   267.694] 6: /lib64/libc.so.6 (__libc_start_main+0xfd) [0x355e21ee5d]
   [   267.694] 7: /usr/bin/X (0x400000+0x21129) [0x421129]
   [   267.694] Segmentation fault at address 0x24
   [   267.694]
   Fatal server error:
   [   267.694] Caught signal 11 (Segmentation fault). Server aborting
   

   my problem here was about the EDID. You can learn about EDID here.
   when i’ve looked again into dmesg log i’ve also noticed this particular entry after connecting the displaylink device:

   [  236.494596] udlfb: Unable to get valid EDID from device/display

2. After some time i found out that this late message was coming from udlfb.c just search for it. It seems that udlfb driver isn’t being able to get the display EDID. As a workaround i’ve connected the monitor to the integrated VGA port on my laptop and ran the following:

   xrandr --prop

   to get myself two 128bit arrays, one for my laptop LCD EDID and a second for the External Monitor connected to the integrated VGA port. Bellow you can see the EDID array for SONY SDM-HS53 Monitor

   EDID:
   		00ffffffffffff004dd9502201010101
   		0b0e01030c1e1778ea8c3ea4584d9124
   		154f51a1080001010101010101010101
   		01010101010164190040410026301888
   		360030e410000018000000fd00393f1c
   		3109000a202020202020000000fc0053
   		444d2d485335330a20202020000000ff
   		00313235333730360a202020202000ce
   

   I’ve also found that fedora provides a set of tools to play with EDIDs. If you are curious and want to try them out issue this:

   yum install monitor-edid

   in the end you can do something like

   xrandr --prop | monitor-parse-edid

   interesting stuff.

3. As a next step I’ve tailored this hexadecimal array into a C array as follows:

   unsigned char sony_sdmhs53_edid[] = {
   0x00,
   0xff,
   0xff,
   0xff,
   0xff,
   0xff,
   0xff,
   0x00,
   0x4d,
   0xd9,
   0x50,
   0x22,
   0x01,
   0x01,
   0x01,
   0x01,
   0x0b,
   0x0e,
   0x01,
   0x03,
   0x0c,
   0x1e,
   0x17,
   0x78,
   0xea,
   0x8c,
   0x3e,
   0xa4,
   0x58,
   0x4d,
   0x91,
   0x24,
   0x15,
   0x4f,
   0x51,
   0xa1,
   0x08,
   0x00,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x01,
   0x64,
   0x19,
   0x00,
   0x40,
   0x41,
   0x00,
   0x26,
   0x30,
   0x18,
   0x88,
   0x36,
   0x00,
   0x30,
   0xe4,
   0x10,
   0x00,
   0x00,
   0x18,
   0x00,
   0x00,
   0x00,
   0xfd,
   0x00,
   0x39,
   0x3f,
   0x1c,
   0x31,
   0x09,
   0x00,
   0x0a,
   0x20,
   0x20,
   0x20,
   0x20,
   0x20,
   0x20,
   0x00,
   0x00,
   0x00,
   0xfc,
   0x00,
   0x53,
   0x44,
   0x4d,
   0x2d,
   0x48,
   0x53,
   0x35,
   0x33,
   0x0a,
   0x20,
   0x20,
   0x20,
   0x20,
   0x00,
   0x00,
   0x00,
   0xff,
   0x00,
   0x31,
   0x32,
   0x35,
   0x33,
   0x37,
   0x30,
   0x36,
   0x0a,
   0x20,
   0x20,
   0x20,
   0x20,
   0x20,
   0x00,
   0xce,
   };
   

   and added this to udlfb.c

4. The next step was to hardcode the EDID in udlfb.c since it wasn’t being able to successfully get it dynamically through the USB device.
   Below you can see the changes i’ve made

   Binary files udlfb.git/.git/index and udlfb.new/.git/index differ
   diff -uNrp udlfb.git/.git/logs/HEAD udlfb.new/.git/logs/HEAD
   --- udlfb.git/.git/logs/HEAD	2011-09-23 00:02:10.376129589 +0100
   +++ udlfb.new/.git/logs/HEAD	2011-09-22 04:46:35.000000000 +0100
   @@ -1 +1 @@
   -0000000000000000000000000000000000000000 1811e5c48a29cc925f9b7a49465e06255196a80f Nuno M Reis  1316732530 +0100	clone: from http://git.plugable.com/webdav/udlfb
   +0000000000000000000000000000000000000000 1811e5c48a29cc925f9b7a49465e06255196a80f root  1316663195 +0100	clone: from http://git.plugable.com/webdav/udlfb
   diff -uNrp udlfb.git/.git/logs/refs/heads/master udlfb.new/.git/logs/refs/heads/master
   --- udlfb.git/.git/logs/refs/heads/master	2011-09-23 00:02:10.376129589 +0100
   +++ udlfb.new/.git/logs/refs/heads/master	2011-09-22 04:46:35.000000000 +0100
   @@ -1 +1 @@
   -0000000000000000000000000000000000000000 1811e5c48a29cc925f9b7a49465e06255196a80f Nuno M Reis  1316732530 +0100	clone: from http://git.plugable.com/webdav/udlfb
   +0000000000000000000000000000000000000000 1811e5c48a29cc925f9b7a49465e06255196a80f root  1316663195 +0100	clone: from http://git.plugable.com/webdav/udlfb
   diff -uNrp udlfb.git/udlfb.c udlfb.new/udlfb.c
   --- udlfb.git/udlfb.c	2011-09-23 00:02:10.379129638 +0100
   +++ udlfb.new/udlfb.c	2011-09-22 05:56:36.000000000 +0100
   @@ -75,6 +75,138 @@ static int console = 1; /* Allow fbcon t
    static int fb_defio = 1;  /* Detect mmap writes using page faults */
    static int shadow = 1; /* Optionally disable shadow framebuffer */
    
   +
   +unsigned char sony_sdmhs53_edid[] = {
   +0x00,
   +0xff,
   +0xff,
   +0xff,
   +0xff,
   +0xff,
   +0xff,
   +0x00,
   +0x4d,
   +0xd9,
   +0x50,
   +0x22,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x0b,
   +0x0e,
   +0x01,
   +0x03,
   +0x0c,
   +0x1e,
   +0x17,
   +0x78,
   +0xea,
   +0x8c,
   +0x3e,
   +0xa4,
   +0x58,
   +0x4d,
   +0x91,
   +0x24,
   +0x15,
   +0x4f,
   +0x51,
   +0xa1,
   +0x08,
   +0x00,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x01,
   +0x64,
   +0x19,
   +0x00,
   +0x40,
   +0x41,
   +0x00,
   +0x26,
   +0x30,
   +0x18,
   +0x88,
   +0x36,
   +0x00,
   +0x30,
   +0xe4,
   +0x10,
   +0x00,
   +0x00,
   +0x18,
   +0x00,
   +0x00,
   +0x00,
   +0xfd,
   +0x00,
   +0x39,
   +0x3f,
   +0x1c,
   +0x31,
   +0x09,
   +0x00,
   +0x0a,
   +0x20,
   +0x20,
   +0x20,
   +0x20,
   +0x20,
   +0x20,
   +0x00,
   +0x00,
   +0x00,
   +0xfc,
   +0x00,
   +0x53,
   +0x44,
   +0x4d,
   +0x2d,
   +0x48,
   +0x53,
   +0x35,
   +0x33,
   +0x0a,
   +0x20,
   +0x20,
   +0x20,
   +0x20,
   +0x00,
   +0x00,
   +0x00,
   +0xff,
   +0x00,
   +0x31,
   +0x32,
   +0x35,
   +0x33,
   +0x37,
   +0x30,
   +0x36,
   +0x0a,
   +0x20,
   +0x20,
   +0x20,
   +0x20,
   +0x20,
   +0x00,
   +0xce,
   +};
   +
    /*
     * When building as a separate module against an arbitrary kernel,
     * check on build presence of other kernel modules we have dependencies on.
   @@ -814,6 +946,7 @@ error:
    
    #endif
    
   +/*
    static int dlfb_get_edid(struct dlfb_data *dev, char *edid, int len)
    {
    	int i;
   @@ -841,6 +974,7 @@ static int dlfb_get_edid(struct dlfb_dat
    
    	return i;
    }
   +*/
    
    static int dlfb_ops_ioctl(struct fb_info *info, unsigned int cmd,
    				unsigned long arg)
   @@ -1304,20 +1438,23 @@ static int dlfb_setup_modes(struct dlfb_
    			   struct fb_info *info,
    			   char *default_edid, size_t default_edid_size)
    {
   -	int i;
   +	int i,j;
    	const struct fb_videomode *default_vmode = NULL;
    	int result = 0;
   -	char *edid;
   +	char *edid = NULL;
    	int tries = 3;
    
    	if (info->dev) /* only use mutex if info has been registered */
    		mutex_lock(&info->lock);
   -
   +	
    	edid = kmalloc(EDID_LENGTH, GFP_KERNEL);
    	if (!edid) {
    		result = -ENOMEM;
    		goto error;
    	}
   +	for(j = 0; j < EDID_LENGTH; j++){
   +		edid[j] = sony_sdmhs53_edid[j];
   +	}	
    
    	fb_destroy_modelist(&info->modelist);
    	memset(&info->monspecs, 0, sizeof(info->monspecs));
   @@ -1329,11 +1466,13 @@ static int dlfb_setup_modes(struct dlfb_
    	 */
    	while (tries--) {
    
   -		i = dlfb_get_edid(dev, edid, EDID_LENGTH);
   +		i = 128;
    
   -		if (i >= EDID_LENGTH)
   +		if (i >= EDID_LENGTH){
    			fb_edid_to_monspecs(edid, &info->monspecs);
   -
   +			pr_warn("teste\t%x",edid[8]);
   +			pr_warn("teste\t%x",sony_sdmhs53_edid[8]);
   +		}
    		if (info->monspecs.modedb_len > 0) {
    			dev->edid = edid;
    			dev->edid_size = i;
   @@ -1407,8 +1546,8 @@ static int dlfb_setup_modes(struct dlfb_
    		 * default to resolution safe for projectors
    		 * (since they are most common case without EDID)
    		 */
   -		fb_vmode.xres = 800;
   -		fb_vmode.yres = 600;
   +		fb_vmode.xres = 1024;
   +		fb_vmode.yres = 768;
    		fb_vmode.refresh = 60;
    		default_vmode = fb_find_nearest_mode(&fb_vmode,
    						     &info->modelist);
   

   After applying this changes I’ve get ridden of the message I was getting earlier.

   [  236.494596] udlfb: Unable to get valid EDID from device/display

5. Let’s go back to step no. 7 above

   startx -- :2 -config xorg.conf.new

   And this time everything worked and i got mayself a new X session running on the displaylink device as primary monitor as seen bellow.

And we are done! 😀
If you intent to use gnome 3 or other 3D features, DisplayLink devices still lack 3D support under Linux. We will have to wait a little bit longer..