[PATCH] Do nothing when there are no platform devices

[Dave Airlie]

On 1 September 2015 at 04:24, Marcin Juszkiewicz
<mjuszkiewicz at redhat.com> wrote:
> https://bugs.freedesktop.org/show_bug.cgi?id=91820
>
> I have APM Mustang (AArch64 (64-bit ARMv8) architecture) on my desk. As
> it has x8 pcie slot I connected Radeon HD5450 graphics card to it. But
> to get X11 running I need to have xorg.conf snippet with BusID set.
>
> Digged into xserver source and found why it happens:
>
> Configure sets CONFIG_UDEV_KMS variable and then XSERVER_PLATFORM_BUS is
> set as well.
>
> Then we have xf86BusProbe() function in hw/xfree86/common/xf86Bus.c
> (xserver source file). If XSERVER_PLATFORM_BUS is defined then
> xf86platformProbe() is called. And then it fails.
>
> But if I disable that block then xf86PciProbe() is called and xserver
> finds PCIe card properly.
>
> So let's check why it fails in xf86platformProbe()...
>
> xf86platformProbe() calls config_odev_probe(xf86PlatformDeviceProbe)
> (argument is callback name)
>
> xf86PlatformDeviceProbe() goes xf86_num_platform_devices times over
> xf86_platform_odev_attributes table to find /dev/dri/card0 entry.
>
> The problem is that xf86_num_platform_devices == 0 so there is nothing
> to search for.
>
That makes sense, but isn't the problem you are having,

why isn't udev picking up the GPU? and setting
xf86_num_platform_devices to 1 is the question you need to answer

pci probing isn't really something we should be relying on.

Dave.

> commit 28defe7722ff4aa09183e67c72e90767539465d2
> Author: Marcin Juszkiewicz <mjuszkiewicz at redhat.com>
> Date:   Mon Aug 31 20:18:11 2015 +0200
>
>     Do nothing if there are no platform devices
>
>     Signed-off-by: Marcin Juszkiewicz <mjuszkiewicz at redhat.com>
>
> diff --git a/hw/xfree86/os-support/linux/lnx_platform.c b/hw/xfree86/os-support/linux/lnx_platform.c
> index 1d145b3..cdc7a89 100644
> --- a/hw/xfree86/os-support/linux/lnx_platform.c
> +++ b/hw/xfree86/os-support/linux/lnx_platform.c
> @@ -151,6 +151,9 @@ xf86PlatformDeviceProbe(struct OdevAttributes *attribs)
>      if (!path)
>          goto out_free;
>
> +    if (!xf86_num_platform_devices)
> +        goto out_free;
> +
>      for (i = 0; i < xf86_num_platform_devices; i++) {
>          char *dpath = xf86_platform_odev_attributes(i)->path;
>
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