usb: Enforce that there can only be one USB event source for now.

[libsigrok.git] / hardware / common / usb.c

diff --git a/hardware/common/usb.c b/hardware/common/usb.c
index 64f887de91458c7a0ac75ff6c89168dba5170ff8..c4d78f90a236acd036c4ad7e60a1ea902f225fa1 100644 (file)
--- a/hardware/common/usb.c
+++ b/hardware/common/usb.c
@@ -277,6 +277,11 @@ SR_PRIV int usb_callback(int fd, int revents, void *cb_data)
 SR_PRIV int usb_source_add(struct sr_context *ctx, int timeout,
                sr_receive_data_callback_t cb, void *cb_data)
 {
+       if (ctx->usb_source_present) {
+               sr_err("A USB event source is already present.");
+               return SR_ERR;
+       }
+
 #ifdef _WIN32
        ctx->usb_event = CreateEvent(NULL, TRUE, FALSE, NULL);
        g_mutex_init(&ctx->usb_mutex);
@@ -296,12 +301,16 @@ SR_PRIV int usb_source_add(struct sr_context *ctx, int timeout,
                sr_source_add(lupfd[i]->fd, lupfd[i]->events, timeout, cb, cb_data);
        free(lupfd);
 #endif
+       ctx->usb_source_present = TRUE;
 
        return SR_OK;
 }
 
 SR_PRIV int usb_source_remove(struct sr_context *ctx)
 {
+       if (!ctx->usb_source_present)
+               return SR_OK;
+
 #ifdef _WIN32
        ctx->usb_thread_running = FALSE;
        g_mutex_unlock(&ctx->usb_mutex);
@@ -319,6 +328,7 @@ SR_PRIV int usb_source_remove(struct sr_context *ctx)
                sr_source_remove(lupfd[i]->fd);
        free(lupfd);
 #endif
+       ctx->usb_source_present = FALSE;
 
        return SR_OK;
 }