PCI: Add pci_irq_type() to query the allocated interrupt typegrafted

Add a helper that returns PCI_IRQ_MSIX, PCI_IRQ_MSI, or PCI_IRQ_INTX
based on the interrupt type the PCI core selected after
pci_alloc_irq_vectors().

Several drivers already open-code this check against pdev->msix_enabled
and pdev->msi_enabled, or even open code this helper [1].

A common helper avoids the duplication and keeps drivers from accessing
the bitfield directly (see also [2]).

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: John Hubbard <jhubbard@nvidia.com>
Link: https://elixir.bootlin.com/linux/v7.1/source/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c#L196 [1]
Inspired-by: John Hubbard <jhubbard@nvidia.com>
Link: https://lore.kernel.org/all/DKKG2QM3YJYB.Z2H2B2UXJ75N@kernel.org/ [2]
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260813165234.620555-5-dakr@kernel.org
[ Add missing pci_irq_type() stub for CONFIG_PCI=n. ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 82 insertions, 0 deletions

diff --git a/samples/binderfs/binderfs_example.c b/samples/binderfs/binderfs_example.c
new file mode 100644
index 000000000..0fd92cdda
--- /dev/null
+++ b/samples/binderfs/binderfs_example.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <linux/android/binder.h>
+#include <linux/android/binderfs.h>
+
+int main(int argc, char *argv[])
+{
+	int fd, ret, saved_errno;
+	struct binderfs_device device = { 0 };
+
+	ret = unshare(CLONE_NEWNS);
+	if (ret < 0) {
+		fprintf(stderr, "%s - Failed to unshare mount namespace\n",
+			strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0);
+	if (ret < 0) {
+		fprintf(stderr, "%s - Failed to mount / as private\n",
+			strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mkdir("/dev/binderfs", 0755);
+	if (ret < 0 && errno != EEXIST) {
+		fprintf(stderr, "%s - Failed to create binderfs mountpoint\n",
+			strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mount(NULL, "/dev/binderfs", "binder", 0, 0);
+	if (ret < 0) {
+		fprintf(stderr, "%s - Failed to mount binderfs\n",
+			strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	memcpy(device.name, "my-binder", strlen("my-binder"));
+
+	fd = open("/dev/binderfs/binder-control", O_RDONLY | O_CLOEXEC);
+	if (fd < 0) {
+		fprintf(stderr, "%s - Failed to open binder-control device\n",
+			strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	ret = ioctl(fd, BINDER_CTL_ADD, &device);
+	saved_errno = errno;
+	close(fd);
+	errno = saved_errno;
+	if (ret < 0) {
+		fprintf(stderr, "%s - Failed to allocate new binder device\n",
+			strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	printf("Allocated new binder device with major %d, minor %d, and name %s\n",
+	       device.major, device.minor, device.name);
+
+	ret = unlink("/dev/binderfs/my-binder");
+	if (ret < 0) {
+		fprintf(stderr, "%s - Failed to delete binder device\n",
+			strerror(errno));
+		exit(EXIT_FAILURE);
+	}
+
+	/* Cleanup happens when the mount namespace dies. */
+	exit(EXIT_SUCCESS);
+}