sr: fx2lafw: Avoid unnecessary alloc/free combo

In receive_transfer for each completed transfer a new buffer is allocated and
the old one is freed. We can avoid this by simply reusing the buffer for the
next transfer. This is possible if we only resubmit the transfer after all
processing on the data buffer has been done. A new buffer is only allocated if
the size of the old one is not 4096 bytes.

Signed-off-by: Lars-Peter Clausen <redacted>

diff --git a/hardware/fx2lafw/fx2lafw.c b/hardware/fx2lafw/fx2lafw.c
index d38a199923ed6f141f680798cd1369b18b513afc..c03c6b87391726d59d024743d11fe5803da91d9e 100644 (file)
--- a/hardware/fx2lafw/fx2lafw.c
+++ b/hardware/fx2lafw/fx2lafw.c
@@ -696,6 +696,30 @@ static void free_transfer(struct libusb_transfer *transfer)
 
 }
 
+static void resubmit_transfer(struct libusb_transfer *transfer)
+{
+       uint8_t *new_buf;
+
+       /* Increase buffer size to 4096 */
+       if (transfer->length != 4096) {
+               new_buf = g_try_malloc(4096);
+               /* If allocation of the new buffer fails, just vdo not bother and
+                * continue to use the old one. */
+               if (new_buf) {
+                       g_free(transfer->buffer);
+                       transfer->buffer = new_buf;
+                       transfer->length = 4096;
+               }
+       }
+
+       if (libusb_submit_transfer(transfer) != 0) {
+               free_transfer(transfer);
+               /* TODO: Stop session? */
+               /* TODO: Better error message. */
+               sr_err("fx2lafw: %s: libusb_submit_transfer error.", __func__);
+       }
+}
+
 static void receive_transfer(struct libusb_transfer *transfer)
 {
        /* TODO: These statics have to move to the ctx struct. */
@@ -704,7 +728,6 @@ static void receive_transfer(struct libusb_transfer *transfer)
        struct sr_datafeed_logic logic;
        struct context *ctx = transfer->user_data;
        int trigger_offset, i;
-       uint8_t *new_buf;
 
        /*
         * If acquisition has already ended, just free any queued up
@@ -723,21 +746,6 @@ static void receive_transfer(struct libusb_transfer *transfer)
        const int sample_width = ctx->sample_wide ? 2 : 1;
        const int cur_sample_count = transfer->actual_length / sample_width;
 
-       /* Fire off a new request. */
-       if (!(new_buf = g_try_malloc(4096))) {
-               sr_err("fx2lafw: %s: new_buf malloc failed.", __func__);
-               free_transfer(transfer);
-               return; /* TODO: SR_ERR_MALLOC */
-       }
-
-       transfer->buffer = new_buf;
-       transfer->length = 4096;
-       if (libusb_submit_transfer(transfer) != 0) {
-               /* TODO: Stop session? */
-               /* TODO: Better error message. */
-               sr_err("fx2lafw: %s: libusb_submit_transfer error.", __func__);
-       }
-
        if (transfer->actual_length == 0) {
                empty_transfer_count++;
                if (empty_transfer_count > MAX_EMPTY_TRANSFERS) {
@@ -746,8 +754,10 @@ static void receive_transfer(struct libusb_transfer *transfer)
                         * will work out that the samplecount is short.
                         */
                        abort_acquisition(ctx);
+                       free_transfer(transfer);
+               } else {
+                       resubmit_transfer(transfer);
                }
-               g_free(cur_buf);
                return;
        } else {
                empty_transfer_count = 0;
@@ -832,7 +842,8 @@ static void receive_transfer(struct libusb_transfer *transfer)
                 * ratio-sized buffer.
                 */
        }
-       g_free(cur_buf);
+
+       resubmit_transfer(transfer);
 }
 
 static int hw_dev_acquisition_start(int dev_index, void *cb_data)