loader: add gpu selection code via DRI_PRIME.

v2: Fix the leak of device_name
v3: Rebased

It enables to use the DRI_PRIME env var to specify
which gpu to use.
Two syntax are supported:
If DRI_PRIME is 1 it means: take any other gpu than the default one.
If DRI_PRIME is the ID_PATH_TAG of a device: choose this device if
possible.

The ID_PATH_TAG is a tag filled by udev.
You can check it with 'udevadm info' on the device node.
For example it can be "pci-0000_01_00_0".

Render-nodes need to be enabled to choose another gpu,
and they need to have the ID_PATH_TAG advertised.
It is possible for not very recent udev that the tag
is not advertised for render-nodes, then
ones need to add a file containing:

SUBSYSTEM=="drm", IMPORT{builtin}="path_id"

in /etc/udev/rules.d/

Signed-off-by: Axel Davy <[email protected]>
Reviewed-by: Emil Velikov <[email protected]>
Signed-off-by: Dave Airlie <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/loader/loader.h b/src/loader/loader.h
index dfd77baad0e..fa57950de2c 100644
--- a/src/loader/loader.h
+++ b/src/loader/loader.h
@@ -41,6 +41,13 @@ loader_get_driver_for_fd(int fd, unsigned driver_types);
 char *
 loader_get_device_name_for_fd(int fd);
 
+/* Function to get a different device than the one we are to use by default,
+ * if the user requests so and it is possible. The initial fd will be closed
+ * if neccessary. The returned fd is potentially a render-node.
+ */
+
+int
+loader_get_user_preferred_fd(int default_fd, int *different_device);
 
 /* for logging.. keep this aligned with egllog.h so we can just use
  * _eglLog directly.