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vcgencmd: Make use of more restricted vcio_gencmd node if available #178

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Merged
pelwell merged 1 commit into from
May 11, 2026
+14 −10
Merged

vcgencmd: Make use of more restricted vcio_gencmd node if available #178

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24 changes: 14 additions & 10 deletions vcgencmd/vcgencmd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,9 +37,10 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include <unistd.h>
#include <sys/ioctl.h> /* ioctl */

#define DEVICE_FILE_NAME "/dev/vcio"
#define MAJOR_NUM 100
#define IOCTL_MBOX_PROPERTY _IOWR(MAJOR_NUM, 0, char *)
#define countof(x) (sizeof x/sizeof *x)

#define VCIO_IOC_MAGIC 100
#define IOCTL_MBOX_PROPERTY _IOWR(VCIO_IOC_MAGIC, 0, char *)

#define MAX_STRING 1024

Expand All @@ -61,15 +62,18 @@ static int mbox_property(int file_desc, void *buf)
static int mbox_open()
{
int file_desc;

const char *devices[] = {"/dev/vcio_gencmd", "/dev/vcio"};
int i;
// open a char device file used for communicating with kernel mbox driver
file_desc = open(DEVICE_FILE_NAME, 0);
if (file_desc < 0) {
printf("Can't open device file: %s\n", DEVICE_FILE_NAME);
printf("Try creating a device file with: sudo mknod %s c %d 0\n", DEVICE_FILE_NAME, MAJOR_NUM);
exit(-1);
// first try the more restrictive interface but fall back to full if unavailable
for (i=0; i<countof(devices); i++)
{
file_desc = open(devices[i], 0);
if (file_desc >= 0)
return file_desc;
}
return file_desc;
printf("Can't open device file: %s\n", devices[0]);
exit(-1);
}

static void mbox_close(int file_desc) {
Expand Down