[PATCH v4l-utils] v4l2-compliance: Add an option to override the driver name

[PATCH v4l-utils] v4l2-compliance: Add an option to override the driver name

[Brian Daniels]

When using the virtio-media driver, the host and a guest VM are used,
with the guest VM proxying requests to a host device. The driver name in
the guest VM is reported as "virtio-media", when really its proxying
requests to a driver with a different name (for example, "uvcvideo").
For the test to pass, v4l2-compliance needs to know the driver name of
the device on the host because it changes its behavior depending on the
driver under test.

With this new option, the name of the host driver can be passed in on
the command line so the test running in the guest can adapt accordingly.

Assisted-by: Gemini CLI:gemini-3.1-pro
Signed-off-by: Brian Daniels <briandaniels@google.com>
---
 utils/v4l2-compliance/v4l2-compliance.cpp | 17 +++++++++++++++++
 utils/v4l2-compliance/v4l2-compliance.h   | 15 ++++++++++++++-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/utils/v4l2-compliance/v4l2-compliance.cpp b/utils/v4l2-compliance/v4l2-compliance.cpp
index 4e5c9d00..ddb4e7a7 100644
--- a/utils/v4l2-compliance/v4l2-compliance.cpp
+++ b/utils/v4l2-compliance/v4l2-compliance.cpp
@@ -52,6 +52,7 @@ enum Option {
 	OptHelp = 'h',
 	OptSetMediaDevice = 'm',
 	OptSetMediaDeviceOnly = 'M',
+	OptDriverName = 'N',
 	OptNoWarnings = 'n',
 	OptNoProgress = 'P',
 	OptSetRadioDevice = 'r',
@@ -87,6 +88,7 @@ bool exit_on_warn;
 bool is_vivid;
 bool is_uvcvideo;
 int media_fd = -1;
+std::string override_driver_name;
 unsigned warnings;
 bool has_mmu = true;
 
@@ -130,6 +132,7 @@ static struct option long_options[] = {
 	{"help", no_argument, nullptr, OptHelp},
 	{"verbose", no_argument, nullptr, OptVerbose},
 	{"color", required_argument, nullptr, OptColor},
+	{"driver-name", required_argument, nullptr, OptDriverName},
 	{"no-warnings", no_argument, nullptr, OptNoWarnings},
 	{"no-progress", no_argument, nullptr, OptNoProgress},
 	{"exit-on-fail", no_argument, nullptr, OptExitOnFail},
@@ -255,6 +258,8 @@ static void usage()
 	printf("                     then this defaults to 90%%.\n");
 	printf("  -E, --exit-on-fail Exit on the first fail.\n");
 	printf("  -h, --help         Display this help message.\n");
+	printf("  -N, --driver-name <name>\n");
+	printf("                     Override driver name with <name>.\n");
 	printf("  -C, --color <when> Highlight OK/warn/fail/FAIL strings with colors\n");
 	printf("                     <when> can be set to always, never, or auto (the default)\n");
 	printf("  -n, --no-warnings  Turn off warning messages.\n");
@@ -1026,6 +1031,15 @@ void testNode(struct node &node, struct node &node_m2m_cap, struct node &expbuf_
 		printf("Compliance test for device ");
 	else
 		printf("Compliance test for %s device ", driver.c_str());
+
+	struct v4l2_capability real_vcap;
+	node.querycap(real_vcap);
+
+	std::string real_vcap_driver = reinterpret_cast<const char *>(real_vcap.driver);
+	if (driver != real_vcap_driver) {
+		printf("(overridden from %s) ", real_vcap_driver.c_str());
+	}
+
 	printf("%s%s:\n\n", node.device, node.g_direct() ? "" : " (using libv4l2)");
 
 	if (node.g_caps() & (V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_VBI_CAPTURE |
@@ -1811,6 +1825,9 @@ int main(int argc, char **argv)
 				}
 			}
 			break;
+		case OptDriverName:
+			override_driver_name = optarg;
+			break;
 		case OptColor:
 			if (!strcmp(optarg, "always"))
 				show_colors = true;
diff --git a/utils/v4l2-compliance/v4l2-compliance.h b/utils/v4l2-compliance/v4l2-compliance.h
index 4a7af5f5..563075c6 100644
--- a/utils/v4l2-compliance/v4l2-compliance.h
+++ b/utils/v4l2-compliance/v4l2-compliance.h
@@ -311,7 +311,20 @@ static inline double fract2f(const struct v4l2_fract *f)
 	return (double)f->numerator / (double)f->denominator;
 }
 
-#define doioctl(n, r, p) v4l_named_ioctl((n)->g_v4l_fd(), #r, r, p)
+extern std::string override_driver_name;
+
+inline int wrapped_doioctl(struct node *n, const char *name, unsigned long cmd, void *arg)
+{
+	int retval = v4l_named_ioctl(n->g_v4l_fd(), name, cmd, arg);
+	if (retval == 0 && cmd == VIDIOC_QUERYCAP && arg != nullptr && !override_driver_name.empty()) {
+		struct v4l2_capability *cap = (struct v4l2_capability *)arg;
+		strncpy((char *)cap->driver, override_driver_name.c_str(), sizeof(cap->driver) - 1);
+		cap->driver[sizeof(cap->driver) - 1] = '\0';
+	}
+	return retval;
+}
+
+#define doioctl(n, r, p) wrapped_doioctl(n, #r, r, p)
 
 const char *ok(int res);
 int check_string(const char *s, size_t len);

base-commit: f2a3cb8a59bcce9ac9f7a7c5b71429610d638a12
-- 
2.54.0.794.g4f17f83d09-goog