diff options
Diffstat (limited to 'recipes-demo/de10-nano-gpio-apps/files/show_KEY0_pb_state.c')
| -rw-r--r-- | recipes-demo/de10-nano-gpio-apps/files/show_KEY0_pb_state.c | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/recipes-demo/de10-nano-gpio-apps/files/show_KEY0_pb_state.c b/recipes-demo/de10-nano-gpio-apps/files/show_KEY0_pb_state.c new file mode 100644 index 0000000..c243a73 --- /dev/null +++ b/recipes-demo/de10-nano-gpio-apps/files/show_KEY0_pb_state.c @@ -0,0 +1,186 @@ +#include <stdio.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <error.h> +#include <errno.h> +#include <limits.h> +#include <unistd.h> +#include <dirent.h> +#include <string.h> + +int main(void) { + DIR *gpio_dir; + const char *gpio_dir_path = "/sys/class/gpio"; + const char *gpiochip_str = "gpiochip"; + const char *gpio_label = "gpio@0x100005000"; + size_t gpiochip_str_len = strlen(gpiochip_str); + int result; + struct dirent *dir_entry; + char path[PATH_MAX]; + int path_length; + int file_fd; + char buffer[PATH_MAX + 1] = {0}; + char gpio_number_buffer[PATH_MAX + 1] = {0}; + char *str_result = NULL; + char *newline_ptr; + + // open the sysfs gpio directory + gpio_dir = opendir(gpio_dir_path); + if(gpio_dir == NULL) + error(1, errno, "could not open directory '%s'", gpio_dir_path); + + // find the gpio controller for the KEY0 push button 'gpio@0x100005000' + while(1) { + // read the next directory entry + errno = 0; + dir_entry = readdir(gpio_dir); + if(dir_entry == NULL) { + if(errno != 0) + error(1, errno, "reading directory '%s'", + gpio_dir_path); + else + break; + } + + // check if this is a gpio controller entry + result = strncmp(dir_entry->d_name, gpiochip_str, + gpiochip_str_len); + if(result != 0) + continue; + + // open the gpio controller label file and read label value + path_length = snprintf(path, PATH_MAX, "%s/%s/label", + gpio_dir_path, dir_entry->d_name); + if(path_length < 0) + error(1, 0, "path output error"); + if(path_length >= PATH_MAX) + error(1, 0, "path length overflow"); + + file_fd = open(path, O_RDONLY | O_SYNC); + if(file_fd < 0) + error(1, errno, "could not open file '%s'", path); + + result = read(file_fd, buffer, PATH_MAX); + if(result < 0) + error(1, errno, "reading from '%s'", path); + if(result == PATH_MAX) + error(1, errno, "buffer overflow reading '%s'", path); + + result = close(file_fd); + if(result < 0) + error(1, errno, "could not close file '%s'", path); + + buffer[PATH_MAX] = 0; + // test the gpio controller label value for our gpio controller + str_result = strstr(buffer, gpio_label); + if(str_result != NULL) + break; + } + + if(str_result == NULL) + error(1, 0, "unable to locate gpio controller"); + + // open the gpio controller base file and read base value + path_length = snprintf(path, PATH_MAX, "%s/%s/base", + gpio_dir_path, dir_entry->d_name); + if(path_length < 0) + error(1, 0, "path output error"); + if(path_length >= PATH_MAX) + error(1, 0, "path length overflow"); + + file_fd = open(path, O_RDONLY | O_SYNC); + if(file_fd < 0) + error(1, errno, "could not open file '%s'", path); + + result = read(file_fd, gpio_number_buffer, PATH_MAX); + if(result < 0) + error(1, errno, "reading from '%s'", path); + if(result == PATH_MAX) + error(1, errno, "buffer overflow reading '%s'", path); + + result = close(file_fd); + if(result < 0) + error(1, errno, "could not close file '%s'", path); + + gpio_number_buffer[PATH_MAX] = 0; + // remove the newline at the end of the string + newline_ptr = strchr(gpio_number_buffer,'\n'); + if(newline_ptr != NULL) + memset(newline_ptr, '\0', 1); + + // open the gpio export file and write our gpio number + path_length = snprintf(path, PATH_MAX, "%s/export", + gpio_dir_path); + if(path_length < 0) + error(1, 0, "path output error"); + if(path_length >= PATH_MAX) + error(1, 0, "path length overflow"); + + file_fd = open(path, O_WRONLY | O_SYNC); + if(file_fd < 0) + error(1, errno, "could not open file '%s'", path); + + result = write(file_fd, gpio_number_buffer, strlen(gpio_number_buffer)); + // NOTE: we don't bother checking for errors here because if this gpio + // has already been exported this write will receive a device busy error + // which is perfectly normal. + + result = close(file_fd); + if(result < 0) + error(1, errno, "could not close file '%s'", path); + + // open the gpio value file and read the value + path_length = snprintf(path, PATH_MAX, "%s/gpio%s/value", + gpio_dir_path, gpio_number_buffer); + if(path_length < 0) + error(1, 0, "path output error"); + if(path_length >= PATH_MAX) + error(1, 0, "path length overflow"); + + file_fd = open(path, O_RDONLY | O_SYNC); + if(file_fd < 0) + error(1, errno, "could not open file '%s'", path); + + result = read(file_fd, buffer, PATH_MAX); + if(result < 0) + error(1, errno, "reading from '%s'", path); + if(result == PATH_MAX) + error(1, errno, "buffer overflow reading '%s'", path); + + result = close(file_fd); + if(result < 0) + error(1, errno, "could not close file '%s'", path); + + buffer[PATH_MAX] = 0; + // remove the newline at the end of the string + newline_ptr = strchr(buffer,'\n'); + if(newline_ptr != NULL) + memset(newline_ptr, '\0', 1); + + // print the KEY0 push button state value + printf("KEY0 push button is at state '%s'\n", buffer); + + // open the gpio unexport file and write our gpio number + path_length = snprintf(path, PATH_MAX, "%s/unexport", + gpio_dir_path); + if(path_length < 0) + error(1, 0, "path output error"); + if(path_length >= PATH_MAX) + error(1, 0, "path length overflow"); + + file_fd = open(path, O_WRONLY | O_SYNC); + if(file_fd < 0) + error(1, errno, "could not open file '%s'", path); + + result = write(file_fd, gpio_number_buffer, strlen(gpio_number_buffer)); + if(result < 0) + error(1, errno, "writing to '%s'", path); + if((size_t)(result) != strlen(gpio_number_buffer)) + error(1, errno, "buffer underflow writing '%s'", path); + + result = close(file_fd); + if(result < 0) + error(1, errno, "could not close file '%s'", path); +} + |