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Initialize the usb library only once

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Initializing the hidapi library more than once is tricky. The hid_init()
function can be called multiple times, but the the hid_exit() function
will free the resources unconditionally, regardless of how many times
the hid_init() function has been called. The consequence is a premature
termination of the library.

To avoid this problem, the calls are reference counted. Note that this
workaround can't protect against calls made outside the libdivecomputer
code!

The libusb library doesn't suffer from this problem, because each
initialization returns a new context pointer. But for consistency, we
now also use a single reference counted libusb context.
This commit is contained in:
Jef Driesen 2017-09-25 23:50:55 +02:00
parent efe2edd83c
commit 7b920f5c42
1 changed files with 66 additions and 30 deletions
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96
src/usbhid.c
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@ -52,7 +52,6 @@ struct dc_usbhid_t {
dc_context_t *context;
/* Internal state. */
#if defined(USE_LIBUSB)
libusb_context *ctx;
libusb_device_handle *handle;
int interface;
unsigned char endpoint_in;
@ -87,13 +86,65 @@ syserror(int errcode)
}
#endif
#ifdef USBHID
static size_t g_usbhid_refcount = 0;
#ifdef USE_LIBUSB
static libusb_context *g_usbhid_ctx = NULL;
#endif
static dc_status_t
dc_usbhid_init (dc_context_t *context)
{
dc_status_t status = DC_STATUS_SUCCESS;
if (g_usbhid_refcount == 0) {
#if defined(USE_LIBUSB)
int rc = libusb_init (&g_usbhid_ctx);
if (rc != LIBUSB_SUCCESS) {
ERROR (context, "Failed to initialize usb support (%s).",
libusb_error_name (rc));
status = syserror (rc);
goto error;
}
#elif defined(USE_HIDAPI)
int rc = hid_init();
if (rc < 0) {
ERROR (context, "Failed to initialize usb support.");
status = DC_STATUS_IO;
goto error;
}
#endif
}
g_usbhid_refcount++;
error:
return status;
}
static dc_status_t
dc_usbhid_exit (void)
{
if (--g_usbhid_refcount == 0) {
#if defined(USE_LIBUSB)
libusb_exit (g_usbhid_ctx);
g_usbhid_ctx = NULL;
#elif defined(USE_HIDAPI)
hid_exit ();
#endif
}
return DC_STATUS_SUCCESS;
}
#endif
dc_status_t
dc_usbhid_open (dc_usbhid_t **out, dc_context_t *context, unsigned int vid, unsigned int pid)
{
#ifdef USBHID
dc_status_t status = DC_STATUS_SUCCESS;
dc_usbhid_t *usbhid = NULL;
int rc = 0;
if (out == NULL)
return DC_STATUS_INVALIDARGS;
@ -110,21 +161,19 @@ dc_usbhid_open (dc_usbhid_t **out, dc_context_t *context, unsigned int vid, unsi
// Library context.
usbhid->context = context;
#if defined(USE_LIBUSB)
struct libusb_device **devices = NULL;
struct libusb_config_descriptor *config = NULL;
// Initialize the libusb library.
rc = libusb_init (&usbhid->ctx);
if (rc != LIBUSB_SUCCESS) {
ERROR (context, "Failed to initialize usb support (%s).",
libusb_error_name (rc));
status = syserror (rc);
// Initialize the usb library.
status = dc_usbhid_init (context);
if (status != DC_STATUS_SUCCESS) {
goto error_free;
}
#if defined(USE_LIBUSB)
struct libusb_device **devices = NULL;
struct libusb_config_descriptor *config = NULL;
int rc = 0;
// Enumerate the USB devices.
ssize_t ndevices = libusb_get_device_list (usbhid->ctx, &devices);
ssize_t ndevices = libusb_get_device_list (g_usbhid_ctx, &devices);
if (ndevices < 0) {
ERROR (context, "Failed to enumerate the usb devices (%s).",
libusb_error_name (ndevices));
@ -243,21 +292,12 @@ dc_usbhid_open (dc_usbhid_t **out, dc_context_t *context, unsigned int vid, unsi
libusb_free_device_list (devices, 1);
#elif defined(USE_HIDAPI)
// Initialize the hidapi library.
rc = hid_init();
if (rc < 0) {
ERROR (context, "Failed to initialize usb support.");
status = DC_STATUS_IO;
goto error_free;
}
// Open the USB device.
usbhid->handle = hid_open (vid, pid, NULL);
if (usbhid->handle == NULL) {
ERROR (context, "Failed to open the usb device.");
status = DC_STATUS_IO;
goto error_hid_exit;
goto error_usb_exit;
}
usbhid->timeout = -1;
@ -274,12 +314,9 @@ error_usb_free_config:
libusb_free_config_descriptor (config);
error_usb_free_list:
libusb_free_device_list (devices, 1);
error_usb_exit:
libusb_exit (usbhid->ctx);
#elif defined(USE_HIDAPI)
error_hid_exit:
hid_exit ();
#endif
error_usb_exit:
dc_usbhid_exit ();
error_free:
free (usbhid);
return status;
@ -300,11 +337,10 @@ dc_usbhid_close (dc_usbhid_t *usbhid)
#if defined(USE_LIBUSB)
libusb_release_interface (usbhid->handle, usbhid->interface);
libusb_close (usbhid->handle);
libusb_exit (usbhid->ctx);
#elif defined(USE_HIDAPI)
hid_close(usbhid->handle);
hid_exit();
#endif
dc_usbhid_exit();
free (usbhid);
return status;