[PATCH] amdgpu: add env support for amdgpu.ids path

[Sergio Costas Rodriguez]

In some cases, like when building a Snap application that uses
libdrm, the `amdgpu.ids` file isn't directly available at the
compiling place, but inside a mounted folder. This forces each
application to link/bind the file from the current place
(usually at the $SNAP/gnome-platform/usr/share/libdrm/amdgpu.ids)
which is cumbersome.

This patch allows to set an environment variable, called
AMDGPU_ASIC_ID_TABLE_PATH, where the file will be also searched
if it isn't located in the default, meson-configured, path.

This patch is also available in the MESA gitlab:
https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/273
---
 README.rst              |  9 +++++++++
 amdgpu/amdgpu_asic_id.c | 14 ++++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/README.rst b/README.rst
index 74608031..6532c12f 100644
--- a/README.rst
+++ b/README.rst
@@ -49,3 +49,12 @@ Then use ninja to build and install:
 
 If you are installing into a system location you will need to run install
 separately, and as root.
+
+AMDGPU ASIC table file
+----------------------
+
+The AMDGPU driver requires the `amdgpu.ids` file. It is usually located at
+`$PREFIX/share/libdrm`, but it is possible to specify an alternative path
+during runtime by setting the `AMDGPU_ASIC_ID_TABLE_PATH` environment
+variable with the full path (including the file name) of the alternative
+file.
diff --git a/amdgpu/amdgpu_asic_id.c b/amdgpu/amdgpu_asic_id.c
index a5007ffc..81a7cf7f 100644
--- a/amdgpu/amdgpu_asic_id.c
+++ b/amdgpu/amdgpu_asic_id.c
@@ -112,10 +112,16 @@ void amdgpu_parse_asic_ids(struct amdgpu_device *dev)
 	ssize_t n;
 	int line_num = 1;
 	int r = 0;
+	const char *amdgpu_asic_id_table_path = getenv("AMDGPU_ASIC_ID_TABLE_PATH");
+
+	if (amdgpu_asic_id_table_path == NULL || amdgpu_asic_id_table_path[0] == '\0') {
+		amdgpu_asic_id_table_path = AMDGPU_ASIC_ID_TABLE;
+	}
+
+	fp = fopen(amdgpu_asic_id_table_path, "r");
 
-	fp = fopen(AMDGPU_ASIC_ID_TABLE, "r");
 	if (!fp) {
-		fprintf(stderr, "%s: %s\n", AMDGPU_ASIC_ID_TABLE,
+		fprintf(stderr, "%s: %s\n", amdgpu_asic_id_table_path,
 			strerror(errno));
 		return;
 	}
@@ -132,7 +138,7 @@ void amdgpu_parse_asic_ids(struct amdgpu_device *dev)
 			continue;
 		}
 
-		drmMsg("%s version: %s\n", AMDGPU_ASIC_ID_TABLE, line);
+		drmMsg("%s version: %s\n", amdgpu_asic_id_table_path, line);
 		break;
 	}
 
@@ -150,7 +156,7 @@ void amdgpu_parse_asic_ids(struct amdgpu_device *dev)
 
 	if (r == -EINVAL) {
 		fprintf(stderr, "Invalid format: %s: line %d: %s\n",
-			AMDGPU_ASIC_ID_TABLE, line_num, line);
+			amdgpu_asic_id_table_path, line_num, line);
 	} else if (r && r != -EAGAIN) {
 		fprintf(stderr, "%s: Cannot parse ASIC IDs: %s\n",
 			__func__, strerror(-r));
-- 
2.45.2