diff options
| -rw-r--r-- | host/arch/arm/lib/crossystem_arch.c | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/host/arch/arm/lib/crossystem_arch.c b/host/arch/arm/lib/crossystem_arch.c index 700622f6..79fb152e 100644 --- a/host/arch/arm/lib/crossystem_arch.c +++ b/host/arch/arm/lib/crossystem_arch.c @@ -18,6 +18,7 @@ #include <sys/ioctl.h> #include <sys/wait.h> #include <dirent.h> +#include <errno.h> #include <fcntl.h> #include <unistd.h> #include <netinet/in.h> @@ -199,13 +200,33 @@ static int gpioline_read_value(int chip_fd, int idx, bool active_low) .lines = 1, }; struct gpiohandle_data data; + int trynum; int ret; - ret = ioctl(chip_fd, GPIO_GET_LINEHANDLE_IOCTL, &request); + /* + * If two callers try to read the same GPIO at the same time then + * one of the two will get back EBUSY. There's no great way to + * solve this, so we'll just retry a bunch with a small sleep in + * between. + */ + for (trynum = 0; true; trynum++) { + ret = ioctl(chip_fd, GPIO_GET_LINEHANDLE_IOCTL, &request); + + /* + * Not part of the loop condition so usleep doesn't clobber + * errno (implicitly used by perror). + */ + if (ret >= 0 || errno != EBUSY || trynum >= 50) + break; + + usleep(trynum * 1000); + } + if (ret < 0) { perror("GPIO_GET_LINEHANDLE_IOCTL"); return -1; } + if (request.fd < 0) { fprintf(stderr, "bad LINEHANDLE fd %d\n", request.fd); return -1; |