I've applied this to libdrm master.
Thanks,
Dave.
On Mon, 26 Oct 2020 at 23:27, Paul Gofman <pgofman@xxxxxxxxxxxxxxx> wrote:
>
> log() is affected by FP control word and can provide inaccurate result.
>
> Fixes Killer Instinct under Wine not being able to find AMD vulkan
> device.
>
> Signed-off-by: Paul Gofman <pgofman@xxxxxxxxxxxxxxx>
> ---
> With the rounding mode the application sets (unsigned int)log2(4) is 1.
> The log2_int() implemetation is copied from radeon/radeon_surface.c.
>
> xf86drm.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/xf86drm.c b/xf86drm.c
> index 50a6f092..dbb7c14b 100644
> --- a/xf86drm.c
> +++ b/xf86drm.c
> @@ -124,6 +124,22 @@ static drmServerInfoPtr drm_server_info;
> static bool drmNodeIsDRM(int maj, int min);
> static char *drmGetMinorNameForFD(int fd, int type);
>
> +static unsigned log2_int(unsigned x)
> +{
> + unsigned l;
> +
> + if (x < 2) {
> + return 0;
> + }
> + for (l = 2; ; l++) {
> + if ((unsigned)(1 << l) > x) {
> + return l - 1;
> + }
> + }
> + return 0;
> +}
> +
> +
> drm_public void drmSetServerInfo(drmServerInfoPtr info)
> {
> drm_server_info = info;
> @@ -4001,7 +4017,7 @@ static void drmFoldDuplicatedDevices(drmDevicePtr local_devices[], int count)
> for (j = i + 1; j < count; j++) {
> if (drmDevicesEqual(local_devices[i], local_devices[j])) {
> local_devices[i]->available_nodes |= local_devices[j]->available_nodes;
> - node_type = log2(local_devices[j]->available_nodes);
> + node_type = log2_int(local_devices[j]->available_nodes);
> memcpy(local_devices[i]->nodes[node_type],
> local_devices[j]->nodes[node_type], drmGetMaxNodeName());
> drmFreeDevice(&local_devices[j]);
> --
> 2.26.2
>
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