[PATCH xorg-gtest 16/16] Add Device::GetDeviceNode() to return device node path from an evemu device

[Chase Douglas]

On 07/02/2012 11:44 PM, Peter Hutterer wrote:
> evemu doesn't export this information and even evemu-device just trawls
> through the file system to print this info. So do the same here, noting the
> time before evemu_create() and the ctime of the new device file. If the
> latter is later than the former and the device names match, we can assume
> this is our device.

I just want to point out that it's a deficiency in uinput, not in evemu, 
in case anyone had any thoughts of trying to fix evemu instead.

> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> ---
>   include/xorg/gtest/evemu/xorg-gtest-device.h |   13 ++++++
>   src/device.cpp                               |   65 +++++++++++++++++++++++++-
>   2 files changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/include/xorg/gtest/evemu/xorg-gtest-device.h b/include/xorg/gtest/evemu/xorg-gtest-device.h
> index 5f8faa2..359e65b 100644
> --- a/include/xorg/gtest/evemu/xorg-gtest-device.h
> +++ b/include/xorg/gtest/evemu/xorg-gtest-device.h
> @@ -75,6 +75,17 @@ class Device {
>      */
>     void Play(const std::string& path) const;
>
> +  /**
> +   * Return the /dev/input/eventX device node for this device.
> +   *
> +   * Note that evemu doesn't know the device node, so we traverse the file
> +   * system looking for it. There is a tiny chance of the device node being
> +   * wrong.
> +   *
> +   * @return The string representing the device node
> +   */
> +  const char* GetDeviceNode(void);
> +
>    private:
>     struct Private;
>     std::auto_ptr<Private> d_;
> @@ -82,6 +93,8 @@ class Device {
>     /* Disable copy constructor & assignment operator */
>     Device(const Device&);
>     Device& operator=(const Device&);
> +
> +  void GuessDeviceNode(time_t ctime);
>   };
>
>   } // namespace evemu
> diff --git a/src/device.cpp b/src/device.cpp
> index 226d4e0..555e3e0 100644
> --- a/src/device.cpp
> +++ b/src/device.cpp
> @@ -28,18 +28,74 @@
>   #include "xorg/gtest/evemu/xorg-gtest-device.h"
>
>   #include <fcntl.h>
> +#include <dirent.h>
>
>   #include <stdexcept>
>
>   #include <gtest/gtest.h>
>
> +#define SYS_INPUT_DIR "/sys/class/input"
> +#define DEV_INPUT_DIR "/dev/input/"
> +
>   struct xorg::testing::evemu::Device::Private {
> -  Private() : fd(-1), device(NULL) {}
> +  Private() : fd(-1), device(NULL), device_node() {}
>
>     int fd;
>     struct evemu_device* device;
> +  std::string device_node;
>   };
>
> +static int _event_device_compare(const struct dirent **a,
> +                                 const struct dirent **b) {
> +  int na, nb;
> +
> +  sscanf((*a)->d_name, "event%d", &na);
> +  sscanf((*b)->d_name, "event%d", &nb);
> +
> +  return (na > nb) ? 1 : (na < nb) ? -1 : 0;
> +
> +}
> +
> +static int _event_device_filter(const struct dirent *d) {
> +  return (strncmp("event", d->d_name, sizeof("event") - 1) == 0);
> +}
> +
> +void xorg::testing::evemu::Device::GuessDeviceNode(time_t ctime) {
> +  struct dirent **event_devices;
> +  int n_event_devices;
> +
> +  n_event_devices = scandir(SYS_INPUT_DIR, &event_devices,
> +                            _event_device_filter, _event_device_compare);
> +
> +  if (n_event_devices < 0) {
> +    std::cerr << "Failed to guess device node." << std::endl;
> +    return;
> +  }
> +
> +  bool found = false;
> +  for (int i = 0; i < n_event_devices && !found; i++) {
> +    std::stringstream s;
> +    s << DEV_INPUT_DIR << event_devices[i]->d_name;
> +
> +    int fd = open(s.str().c_str(), O_RDONLY);
> +    char device_name[256];
> +
> +    ioctl(fd, EVIOCGNAME(sizeof(device_name)), device_name);
> +    if (strcmp(device_name, evemu_get_name(d_->device)) == 0) {
> +      struct stat buf;
> +      if (fstat(fd, &buf) == 0) {
> +        if (buf.st_ctime >= ctime) {
> +          d_->device_node = s.str();
> +          found = true;
> +        }
> +      }
> +    }
> +    close(fd);
> +    free(event_devices[i]);

We need to free each event device entry, but if we break out of the 
loops early because we've found a matching device, then we won't free 
the rest of the devices in the array.

> +  }
> +  free(event_devices);
> +}
> +
>   xorg::testing::evemu::Device::Device(const std::string& path)
>       : d_(new Private) {
>     static const char UINPUT_NODE[] = "/dev/uinput";
> @@ -68,11 +124,14 @@ xorg::testing::evemu::Device::Device(const std::string& path)
>       throw std::runtime_error("Failed to open uinput node");
>     }
>
> +  time_t ctime = time(NULL);
>     if (evemu_create(d_->device, d_->fd) < 0) {
>       close(d_->fd);
>       evemu_delete(d_->device);
>       throw std::runtime_error("Failed to create evemu device");
>     }
> +
> +  GuessDeviceNode(ctime);
>   }
>
>   void xorg::testing::evemu::Device::Play(const std::string& path) const {
> @@ -88,6 +147,10 @@ void xorg::testing::evemu::Device::Play(const std::string& path) const {
>     fclose(file);
>   }
>
> +const char* xorg::testing::evemu::Device::GetDeviceNode(void) {
> +  return d_->device_node.length() > 0 ? d_->device_node.c_str() : NULL;
> +}
> +
>   xorg::testing::evemu::Device::~Device() {
>     close(d_->fd);
>     evemu_delete(d_->device);
>