Add a small utility for retrieving sysfs bus path

From: Mauro Carvalho Chehab <mchehab@redhat.com>

Thanks to Carsten Meier <cm@trexity.de> for providing us a c++ code
snippet for USB.

This code is capable of getting the bus info for both USB and PCI
devices. This is retrieved via bus_info returned by VIDIOC_QUERYCAP.

The utility will output the following info for a usb device:
bus info = usb-0000:00:1d.7-1
bus path = /sys/devices/pci0000:00/0000:00:1d.7/usb2/2-1

And, for PCI devices, it will output:
bus info = PCI:0000:01:02.0
bus path = /sys/devices/pci0000:00/0000:00:1e.0/0000:01:02.0

Notice: This will only work for devices that uses the standard
notation for the bus info:

on PCI:
        sprintf(cap->bus_info, "PCI:%s", pci_name(dev->pci));
or
        sprintf(cap->bus_info, "PCIe:%s", pci_name(dev->pci));

on USB:
	usb_make_path(dev->udev, cap->bus_info, sizeof(cap->bus_info));

Priority: normal

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 168 insertions, 1 deletions

diff --git a/v4l2-apps/util/Makefile b/v4l2-apps/util/Makefile
index b80de190b..f2c4c0a38 100644
--- a/v4l2-apps/util/Makefile
+++ b/v4l2-apps/util/Makefile
@@ -7,7 +7,7 @@ endif
 CPPFLAGS += -I../include -D_GNU_SOURCE
 LDFLAGS += -lm
 
-binaries = v4l2-ctl v4l2-dbg v4l2-compliance ivtv-ctl cx18-ctl
+binaries = v4l2-ctl v4l2-dbg v4l2-compliance ivtv-ctl cx18-ctl v4l2_sysfs_path
 
 ifeq ($(prefix),)
 prefix = /usr
@@ -34,6 +34,14 @@ v4l2-dbg: v4l2-dbg.o v4l2-chipids.o
 
 v4l2-dbg.o: v4l2-dbg.h v4l2-dbg-bttv.h v4l2-dbg-em28xx.h v4l2-dbg-saa7134.h
 
+v4l2_sysfs_path.o: v4l2_sysfs_path.c ../lib/v4l2_driver.h
+
+v4l2_sysfs_path: v4l2_sysfs_path.o ../lib/libv4l2.a
+	$(CC) $^ -o $@ -lsysfs
+
+../lib/libv4l2.a:
+	$(MAKE) -C ../lib libv4l2.a
+
 install:
 	mkdir -p $(prefix)/bin
 	cp $(binaries) $(prefix)/bin
diff --git a/v4l2-apps/util/v4l2_sysfs_path.c b/v4l2-apps/util/v4l2_sysfs_path.c
new file mode 100644
index 000000000..c2d754ed2
--- /dev/null
+++ b/v4l2-apps/util/v4l2_sysfs_path.c
@@ -0,0 +1,159 @@
+/*
+    Copyright (C) 2009 Mauro Carvalho Chehab <mchehab@redhat.com>
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation version 2 of the License.
+
+    The sysfs logic were adapted from a C++/Boost snippet code sent by
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+
+
+#include "../lib/v4l2_driver.h"
+#include <sysfs/libsysfs.h>
+#include <errno.h>
+#include <malloc.h>
+#include <stdio.h>
+#include <string.h>
+
+#define USB_ID "usb-"
+#define PCI_ID "PCI:"
+#define PCIe_ID "PCIe:"
+
+char *obtain_bus_sysfs_path(const char *bus_info)
+{
+	struct sysfs_device *pcictl = NULL;
+	struct sysfs_bus *bus = NULL;
+	struct sysfs_device *busdev = NULL;
+	struct dlist *busdevs = NULL;
+	struct sysfs_device *pdev = NULL;
+	char *tmp = NULL, *busname, *buspath;
+	int pci;
+
+	if (!strncmp(bus_info, USB_ID, strlen(USB_ID))) {
+		bus_info += strlen(USB_ID);
+		pci = 0;
+	} else 	if (!strncmp(bus_info, PCI_ID, strlen(PCI_ID))) {
+		bus_info += strlen(PCI_ID);
+		pci = 1;
+	} else 	if (!strncmp(bus_info, PCIe_ID, strlen(PCIe_ID))) {
+		bus_info += strlen(PCIe_ID);
+		pci = 1;
+	} else
+		return NULL;
+
+	busname = strtok(bus_info, "-");
+	if (!busname)
+		return NULL;
+
+	buspath = strtok(NULL, "-");
+	if (!buspath && !pci)
+		return NULL;
+
+	/* open bus host controller */
+	pcictl = sysfs_open_device("pci", busname);
+	if (!pcictl)
+		goto err;
+
+	/* We have all we need for PCI devices */
+	if (pci) {
+		char *name;
+
+		asprintf(&name, "%s", pcictl->path);
+		return name;
+	}
+
+	/* find matching usb bus */
+	bus = sysfs_open_bus("usb");
+	if (!bus)
+		goto err;
+
+	busdevs = sysfs_get_bus_devices(bus);
+	if (!busdevs)
+		goto err;
+
+	dlist_for_each_data(busdevs, busdev, struct sysfs_device) {
+		/* compare pathes of bus host controller and
+		   parent of enumerated bus devices */
+
+		pdev = sysfs_get_device_parent(busdev);
+		if (!pdev)
+			continue;
+
+		if (!strcmp(pcictl->path, pdev->path))
+			break;
+	}
+
+	if (!pdev)
+		goto err;
+
+	sysfs_close_device(pcictl);
+	pcictl = NULL;
+
+	/* assemble bus device path */
+	if (busdev) {
+		struct sysfs_attribute *busnumattr;
+		unsigned int busnum;
+		char *name;
+
+		busnumattr = sysfs_get_device_attr(busdev, "busnum");
+		if (!busnumattr)
+			goto err;
+
+		tmp = malloc(busnumattr->len + 1);
+		strncpy(tmp, busnumattr->value, busnumattr->len);
+		tmp[busnumattr->len] = '\0';
+
+		if (sscanf(tmp, "%u", &busnum) != 1)
+			goto err;
+
+		asprintf(&name, "%s/%d-%s", busdev->path,
+			 busnum, buspath);
+
+		free(tmp);
+		sysfs_close_bus(bus);
+
+		return name;
+	}
+
+err:
+	if (tmp)
+		free(tmp);
+	if (bus)
+		sysfs_close_bus(bus);
+	if (pcictl)
+		sysfs_close_device(pcictl);
+
+	return NULL;
+}
+
+int main(void)
+{
+	struct v4l2_driver drv;
+	char *path;
+
+	if (v4l2_open("/dev/video0", 0, &drv) < 0) {
+		perror("open /dev/video0");
+		return -1;
+	}
+
+	printf("bus info = %s\n", drv.cap.bus_info);
+	path = obtain_bus_sysfs_path((char *)drv.cap.bus_info);
+	if (path) {
+		printf("bus path = %s\n", path);
+		free(path);
+	}
+
+	v4l2_close(&drv);
+
+	return 0;
+}