[PATCH i-g-t v5 3/8] lib/drmtest: allow opening cards out of order

[Kamil Konieczny]

Current __drm_open_driver_another() implementation prevents
opening cards out of order, for example card 3 without previous
opens of 0..2. This can be seen with three GPU cards system and
gem_open_basic test:

sudo IGT_DEVICE=pci:vendor=Intel,card=all build/tests/gem_basic --r multigpu-create-close

IGT-Version: 1.28-g2548a539e (x86_64) (Linux: 6.7.0-rc5 x86_64)
Using IGT_SRANDOM=1706630533 for randomisation
Opened device: /dev/dri/card0
Starting subtest: multigpu-create-close
<g:0> Testing creating and closing an object.
<g:1> Opened device: /dev/dri/card1
<g:1> Testing creating and closing an object.
gem_basic: ../lib/drmtest.c:341: _is_already_opened: Assertion `as_idx <= _opened_fds_count' failed.
Received signal SIGABRT.

Relax that condition. Also relax condition for filtered devices and
allow them to open already opened ones, basically it will allow
running multi-GPU scenarios on single-GPU system with filter:

IGT_DEVICE=pci:vendor=Intel,card=0\;pci:vendor=Intel,card=0

Changes in __search_and_open() was suggested by Zbigniew.

v5:
 removed caching for names of opened cards
 relaxed opening of filtered devices

Cc: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
Cc: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
Signed-off-by: Kamil Konieczny <kamil.konieczny at linux.intel.com>
---
 lib/drmtest.c | 72 +++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 53 insertions(+), 19 deletions(-)

diff --git a/lib/drmtest.c b/lib/drmtest.c
index 73d9159af..6c6c21b1a 100644
--- a/lib/drmtest.c
+++ b/lib/drmtest.c
@@ -322,35 +322,53 @@ static int _opened_fds_count;
 static void _set_opened_fd(int idx, int fd)
 {
 	assert(idx < ARRAY_SIZE(_opened_fds));
-	assert(idx <= _opened_fds_count);
+	assert(idx >= 0);
 
 	_opened_fds[idx].fd = fd;
 
 	assert(fstat(fd, &_opened_fds[idx].stat) == 0);
 
-	_opened_fds_count = idx+1;
+	for (int n = _opened_fds_count; n < idx; n++)
+		_opened_fds[n].fd = -1;
+
+	if (idx >= _opened_fds_count)
+		_opened_fds_count = idx + 1;
 }
 
-static bool _is_already_opened(const char *path, int as_idx)
+/* in *err returns -errno or index to _opened_fds[] */
+static bool _is_already_opened(const char *path, int as_idx, int *err)
 {
 	struct stat new;
 
 	assert(as_idx < ARRAY_SIZE(_opened_fds));
-	assert(as_idx <= _opened_fds_count);
+	assert(as_idx >= 0);
 
 	/*
 	 * we cannot even stat the device, so it's of no use - let's claim it's
 	 * already opened
 	 */
-	if (igt_debug_on(stat(path, &new) != 0))
+	if (igt_debug_on(stat(path, &new) != 0)) {
+		if (err)
+			*err = -errno;
+
 		return true;
+	}
+
+	if (err)
+		*err = 0;
+
+	for (int i = 0, end = min(_opened_fds_count, as_idx); i < end; ++i) {
+		if (_opened_fds[i].fd == -1)
+			continue;
 
-	for (int i = 0; i < as_idx; ++i) {
 		/* did we cross filesystem boundary? */
 		assert(_opened_fds[i].stat.st_dev == new.st_dev);
 
-		if (_opened_fds[i].stat.st_ino == new.st_ino)
+		if (_opened_fds[i].stat.st_ino == new.st_ino) {
+			*err = i;
+
 			return true;
+		}
 	}
 
 	return false;
@@ -359,23 +377,39 @@ static bool _is_already_opened(const char *path, int as_idx)
 static int __search_and_open(const char *base, int offset, unsigned int chipset, int as_idx)
 {
 	const char *forced;
+	int err;
 
 	forced = forced_driver();
 	if (forced)
 		igt_debug("Force option used: Using driver %s\n", forced);
 
-	for (int i = 0; i < 16; i++) {
+	for (int i = 0, idx = -1; i < 16 && idx < as_idx; i++) {
 		char name[80];
-		int fd;
+		int fd = -1;
 
 		sprintf(name, "%s%u", base, i + offset);
 
-		if (_is_already_opened(name, as_idx))
-			continue;
+		if (_is_already_opened(name, as_idx, &err)) {
+			if (err < 0)
+				continue;
+
+			if (idx + 1 < as_idx) {
+				++idx;
+				continue;
+			}
+		}
+
+		if (err >= 0)
+			fd = __drm_open_device(name, chipset);
+		if (fd != -1) {
+			++idx;
+			if (idx < as_idx) {
+				close(fd);
+				continue;
+			}
 
-		fd = __drm_open_device(name, chipset);
-		if (fd != -1)
 			return fd;
+		}
 	}
 
 	return -1;
@@ -486,8 +520,7 @@ static bool __get_card_for_nth_filter(int idx, struct igt_device_card *card)
  *   * idx-th filter (starting with 0, filters are semicolon separated) is used
  *   * if there is no idx-th filter, goto 2
  *   * first device maching the filter is selected
- *   * if it's already opened (for indexes = 0..idx-1) we fail with -1
- *   * otherwise open the device and return the fd
+ *   * open the device and return the fd
  *
  * 2. compatibility mode - open the first DRM device we can find that is not
  *    already opened for indexes 0..idx-1, searching up to 16 device nodes
@@ -542,11 +575,12 @@ int __drm_open_driver_another(int idx, int chipset)
 		if (!found || !strlen(card.card))
 			igt_warn("No card matches the filter! [%s]\n",
 				 igt_device_filter_get(idx));
-		else if (_is_already_opened(card.card, idx))
-			igt_warn("card maching filter %d is already opened\n", idx);
-		else
-			fd = __open_driver_exact(card.card, chipset);
+		else {
+			int ret;
 
+			_is_already_opened(card.card, idx, &ret); /* check only filesystem boundary */
+			fd = __open_driver_exact(card.card, chipset);
+		}
 	} else {
 		/* no filter for device idx, let's open whatever is available */
 		fd = __open_driver("/dev/dri/card", 0, chipset, idx);
-- 
2.42.0