• Böszörményi Zoltán's avatar
    Fix modesetting device matching through kmsdev device path · 0388e290
    Böszörményi Zoltán authored
    
    
    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"
    EndSection
    
    ...
    
    Section "Device"
            Identifier      "Intel2"
            Driver          "intel"
            BusID           "PCI:0:2:0"
            Screen          2
            Option          "Monitor-HDMI1" "HDMI1"
            Option          "ZaphodHeads" "HDMI1"
    EndSection
    
    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"
    EndSection
    
    ...
    
    Section "Screen"
            Identifier      "SCREEN2"
            Option          "AutoServerLayout" "on"
            Device          "UDL"
            GPUDevice       "Intel2"
            Monitor         "Monitor-DVI-I-1"
            SubSection      "Display"
                    Modes   "1024x768"
                    Depth   24
            EndSubSection
    EndSection
    
    Section "ServerLayout"
            Identifier      "LAYOUT"
            Option          "AutoServerLayout" "on"
            Screen          0 "SCREEN"
            Screen          1 "SCREEN1" RightOf "SCREEN"
            Screen          2 "SCREEN2" RightOf "SCREEN1"
    EndSection
    
    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
    specified.
    
    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 <zboszor@pr.hu>
    0388e290
xf86platformBus.c 21.5 KB