sr: fx2lafw: Calculate buffer size and timeout based on sample rate

[libsigrok.git] / hardware / fx2lafw / fx2lafw.c

diff --git a/hardware/fx2lafw/fx2lafw.c b/hardware/fx2lafw/fx2lafw.c
index fce5472b9e6fb4dfa79ee914d3b7f9cecaa86315..904347969803036ed31729939ac2ec4ba7ee9b9c 100644 (file)
--- a/hardware/fx2lafw/fx2lafw.c
+++ b/hardware/fx2lafw/fx2lafw.c
@@ -698,20 +698,6 @@ 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? */
@@ -860,6 +846,44 @@ static void receive_transfer(struct libusb_transfer *transfer)
        resubmit_transfer(transfer);
 }
 
+static unsigned int to_bytes_per_ms(unsigned int samplerate)
+{
+       return samplerate / 1000;
+}
+
+static size_t get_buffer_size(struct context *ctx)
+{
+       size_t s;
+
+       /* The buffer should be large enough to hold 10ms of data and a multiple
+        * of 512. */
+       s = 10 * to_bytes_per_ms(ctx->cur_samplerate);
+       return (s + 511) & ~511;
+}
+
+static unsigned int get_number_of_transfers(struct context *ctx)
+{
+       unsigned int n;
+
+       /* Total buffer size should be able to hold about 500ms of data */
+       n = 500 * to_bytes_per_ms(ctx->cur_samplerate) / get_buffer_size(ctx);
+
+       if (n > NUM_SIMUL_TRANSFERS)
+               return NUM_SIMUL_TRANSFERS;
+
+       return n;
+}
+
+static unsigned int get_timeout(struct context *ctx)
+{
+       size_t total_size;
+       unsigned int timeout;
+
+       total_size = get_buffer_size(ctx) * get_number_of_transfers(ctx);
+       timeout = total_size / to_bytes_per_ms(ctx->cur_samplerate);
+       return timeout + timeout / 4; /* Leave a headroom of 25% percent */
+}
+
 static int hw_dev_acquisition_start(int dev_index, void *cb_data)
 {
        struct sr_dev_inst *sdi;
@@ -869,7 +893,8 @@ static int hw_dev_acquisition_start(int dev_index, void *cb_data)
        struct context *ctx;
        struct libusb_transfer *transfer;
        const struct libusb_pollfd **lupfd;
-       int ret, size, i;
+       unsigned int i;
+       int ret;
        unsigned char *buf;
 
        if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
@@ -878,9 +903,11 @@ static int hw_dev_acquisition_start(int dev_index, void *cb_data)
        ctx->session_dev_id = cb_data;
        ctx->num_samples = 0;
 
-       /* Start with 2K transfer, subsequently increased to 4K. */
-       size = 2048;
-       for (i = 0; i < NUM_SIMUL_TRANSFERS; i++) {
+       const unsigned int timeout = get_timeout(ctx);
+       const unsigned int num_transfers = get_number_of_transfers(ctx);
+       const size_t size = get_buffer_size(ctx);
+
+       for (i = 0; i < num_transfers; i++) {
                if (!(buf = g_try_malloc(size))) {
                        sr_err("fx2lafw: %s: buf malloc failed.", __func__);
                        return SR_ERR_MALLOC;
@@ -888,7 +915,7 @@ static int hw_dev_acquisition_start(int dev_index, void *cb_data)
                transfer = libusb_alloc_transfer(0);
                libusb_fill_bulk_transfer(transfer, ctx->usb->devhdl,
                                2 | LIBUSB_ENDPOINT_IN, buf, size,
-                               receive_transfer, ctx, 40);
+                               receive_transfer, ctx, timeout);
                if (libusb_submit_transfer(transfer) != 0) {
                        /* TODO: Free them all. */
                        libusb_free_transfer(transfer);
@@ -897,13 +924,12 @@ static int hw_dev_acquisition_start(int dev_index, void *cb_data)
                }
 
                ctx->submitted_transfers++;
-               size = 4096;
        }
 
        lupfd = libusb_get_pollfds(usb_context);
        for (i = 0; lupfd[i]; i++)
                sr_source_add(lupfd[i]->fd, lupfd[i]->events,
-                             40, receive_data, NULL);
+                             timeout, receive_data, NULL);
        free(lupfd); /* NOT g_free()! */
 
        packet.type = SR_DF_HEADER;