asix-sigma: fix buffer length check in register write helper

[libsigrok.git] / src / hardware / asix-sigma / protocol.c

diff --git a/src/hardware/asix-sigma/protocol.c b/src/hardware/asix-sigma/protocol.c
index f17a962332fb08ef0488e0d8c91981778fe43f73..d2670b4c3a974e503330f9a1564fd2b1737772e1 100644 (file)
--- a/src/hardware/asix-sigma/protocol.c
+++ b/src/hardware/asix-sigma/protocol.c
@@ -51,7 +51,7 @@ SR_PRIV const uint64_t samplerates[] = {
        SR_MHZ(200),    /* Special FW needed */
 };
 
-SR_PRIV const int SAMPLERATES_COUNT = ARRAY_SIZE(samplerates);
+SR_PRIV const size_t samplerates_count = ARRAY_SIZE(samplerates);
 
 static const char sigma_firmware_files[][24] = {
        /* 50 MHz, supports 8 bit fractions */
@@ -105,9 +105,9 @@ SR_PRIV int sigma_write_register(uint8_t reg, uint8_t *data, size_t len,
        uint8_t buf[80];
        int idx = 0;
 
-       if ((len + 2) > sizeof(buf)) {
+       if ((2 * len + 2) > sizeof(buf)) {
                sr_err("Attempted to write %zu bytes, but buffer is too small.",
-                      len + 2);
+                      len);
                return SR_ERR_BUG;
        }
 
@@ -523,20 +523,26 @@ SR_PRIV int sigma_set_samplerate(const struct sr_dev_inst *sdi, uint64_t sampler
 {
        struct dev_context *devc;
        struct drv_context *drvc;
-       unsigned int i;
+       size_t i;
        int ret;
 
        devc = sdi->priv;
        drvc = sdi->driver->context;
        ret = SR_OK;
 
-       for (i = 0; i < ARRAY_SIZE(samplerates); i++) {
+       /* Reject rates that are not in the list of supported rates. */
+       for (i = 0; i < samplerates_count; i++) {
                if (samplerates[i] == samplerate)
                        break;
        }
-       if (samplerates[i] == 0)
+       if (i >= samplerates_count || samplerates[i] == 0)
                return SR_ERR_SAMPLERATE;
 
+       /*
+        * Depending on the samplerates of 200/100/50- MHz, specific
+        * firmware is required and higher rates might limit the set
+        * of available channels.
+        */
        if (samplerate <= SR_MHZ(50)) {
                ret = upload_firmware(drvc->sr_ctx, 0, devc);
                devc->num_channels = 16;
@@ -548,6 +554,11 @@ SR_PRIV int sigma_set_samplerate(const struct sr_dev_inst *sdi, uint64_t sampler
                devc->num_channels = 4;
        }
 
+       /*
+        * Derive the sample period from the sample rate as well as the
+        * number of samples that the device will communicate within
+        * an "event" (memory organization internal to the device).
+        */
        if (ret == SR_OK) {
                devc->cur_samplerate = samplerate;
                devc->period_ps = 1000000000000ULL / samplerate;
@@ -555,6 +566,18 @@ SR_PRIV int sigma_set_samplerate(const struct sr_dev_inst *sdi, uint64_t sampler
                devc->state.state = SIGMA_IDLE;
        }
 
+       /*
+        * Support for "limit_samples" is implemented by stopping
+        * acquisition after a corresponding period of time.
+        * Re-calculate that period of time, in case the limit is
+        * set first and the samplerate gets (re-)configured later.
+        */
+       if (ret == SR_OK && devc->limit_samples) {
+               uint64_t msecs;
+               msecs = devc->limit_samples * 1000 / devc->cur_samplerate;
+               devc->limit_msec = msecs;
+       }
+
        return ret;
 }