Commit 42aaf372 authored by Zoltán Böszörményi's avatar Zoltán Böszörményi Committed by Adam Jackson
Browse files

Fix modesetting device matching through kmsdev device path

xf86platformProbeDev didn't check the device path, fix it.

This is a problem when trying to set up a non-PCI device via
explicit xorg.conf.d configuration.

An USB DisplayLink device, being non-PCI was always set up
as a GPU device assigned to screen 0 instead of a regular
framebuffer, potentially having its own dedicated screen,
despite such configuration as below. Only the relevant parts
of the configuration are quoted, it's part of a larger context
with an Intel chip that has 3 outputs:
* DP1 connected to an LCD panel,
* VGA1 connected to an external monitor,
* HDMI1 unconnected and having no user visible connector

Section "ServerFlags"
        Option          "AutoBindGPU" "false"


Section "Device"
        Identifier      "Intel2"
        Driver          "intel"
        BusID           "PCI:0:2:0"
        Screen          2
        Option          "Monitor-HDMI1" "HDMI1"
        Option          "ZaphodHeads" "HDMI1"

Section "Device"
        Identifier      "UDL"
        Driver          "modesetting"
        Option          "kmsdev" "/dev/dri/card0"
        #BusID          "usb:0:1.2:1.0"
        Option          "Monitor-DVI-I-1" "DVI-I-1"
        Option          "ShadowFB" "on"
        Option          "DoubleShadow" "on"


Section "Screen"
        Identifier      "SCREEN2"
        Option          "AutoServerLayout" "on"
        Device          "UDL"
        GPUDevice       "Intel2"
        Monitor         "Monitor-DVI-I-1"
        SubSection      "Display"
                Modes   "1024x768"
                Depth   24

Section "ServerLayout"
        Identifier      "LAYOUT"
        Option          "AutoServerLayout" "on"
        Screen          0 "SCREEN"
        Screen          1 "SCREEN1" RightOf "SCREEN"
        Screen          2 "SCREEN2" RightOf "SCREEN1"

On the particular machine I was trying to set up an UDL device,
I found the following structure was being used to match
the device to a platform device while I was debugging the issue:

xf86_platform_devices[0] == Intel, /dev/dri/card1, primary platform device
xf86_platform_devices[1] == UDL, /dev/dri/card0

devList[0] == "Intel0", ZaphodHeads: DP1
devList[1] == "Intel1", ZaphodHeads: VGA1
devList[2] == "UDL"
devList[3] == "Intel2", ZaphodHeads: HDMI1 (intended GPU device to UDL)

When xf86platformProbeDev() matched the UDL device, the BusID
check failed in both cases of:
* BusID "usb:0:1.2:1.0" was specified
* Option "kmsdev" "/dev/dri/card0" was specified

As a result, xf86platformProbeDev() went on to call probeSingleDevice()
with xf86_platform_devices[0] and devList[2], resulting in the
UDL device being set up as a GPU device assigned to the first screen
instead of as a framebuffer on the third screen as the configuration

Checking Option "kmsdev" in code code may be a layering violation.
But the modesetting driver is actually part of the Xorg sources
instead of being an external driver, so he "kmsdev" path knowledge
may be used here.
Signed-off-by: default avatarBöszörményi Zoltán <>
parent a542224e
......@@ -536,12 +536,20 @@ xf86platformProbeDev(DriverPtr drvp)
/* find the main device or any device specificed in xorg.conf */
for (i = 0; i < numDevs; i++) {
const char *devpath;
/* skip inactive devices */
if (!devList[i]->active)
/* This is specific to modesetting. */
devpath = xf86FindOptionValue(devList[i]->options, "kmsdev");
for (j = 0; j < xf86_num_platform_devices; j++) {
if (devList[i]->busID && *devList[i]->busID) {
if (devpath && *devpath) {
if (strcmp(xf86_platform_devices[j].attribs->path, devpath) == 0)
} else if (devList[i]->busID && *devList[i]->busID) {
if (xf86PlatformDeviceCheckBusID(&xf86_platform_devices[j], devList[i]->busID))
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