[PATCH libdrm 3/3] xf86drm: Add platform and host1x bus support

[Emil Velikov]

On 23 December 2016 at 17:49, Thierry Reding <thierry.reding at gmail.com> wrote:
> From: Thierry Reding <treding at nvidia.com>
>
> ARM SoCs usually have their DRM/KMS devices on the platform bus, so add
> support for that to enable these devices to be used with the drmDevice
> infrastructure.
>
> NVIDIA Tegra SoCs have an additional level in the hierarchy and DRM/KMS
> devices can also be on the host1x bus. This is mostly equivalent to the
> platform bus.
>
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
> Note that we could probably get away with treating host1x as platform
> bus. However, they are technically two different busses in the kernel
> and hence we may want to make use of that differentiation later on.
>
Admittedly there's no clear cut either way, but I'm inclined to have
host1x as platform.
I'm leaning towards that since there is no /sys/bus/host1x (afaict),
plus otherwise devices (like imx-vpu/vc4) will end with their own bus
type.


> +static int drmParsePlatformBusInfo(int maj, int min, drmPlatformBusInfoPtr info)
> +{
> +    char path[PATH_MAX + 1], *name;
> +
> +    snprintf(path, PATH_MAX, "/sys/dev/char/%d:%d/device", maj, min);
> +
> +    name = sysfs_uevent_get(path, "OF_FULLNAME");
> +    strcpy(info->fullname, name);
> +    free(name);
> +
Let's be extra careful and ensure that we don't overrun (and properly
terminate) the fixed size fullname[].


> +    return 0;
> +}
> +
> +static int drmParsePlatformDeviceInfo(int maj, int min,
> +                                      drmPlatformDeviceInfoPtr info)
> +{
> +    /* XXX fill in platform device info */
> +
Not 100% sure what exactly we should consider bus and what device
info, either way an empty struct is not going to go well.
As a food for thought, here is some info for imx/etna and vc4.

cat /sys/dev/char/226\:*/device/uevent

DRIVER=etnaviv
OF_NAME=gpu-subsystem
OF_FULLNAME=/gpu-subsystem
OF_COMPATIBLE_0=fsl,imx-gpu-subsystem
OF_COMPATIBLE_N=1
MODALIAS=of:Ngpu-subsystemT<NULL>Cfsl,imx-gpu-subsystem
DRIVER=imx-drm
OF_NAME=display-subsystem
OF_FULLNAME=/display-subsystem
OF_COMPATIBLE_0=fsl,imx-display-subsystem
OF_COMPATIBLE_N=1

DRIVER=vc4-drm
OF_NAME=gpu
OF_FULLNAME=/soc/gpu
OF_COMPATIBLE_0=brcm,bcm2835-vc4
OF_COMPATIBLE_N=1
MODALIAS=of:NgpuT<NULL>Cbrcm,bcm2835-vc4


Thanks
Emil