usrp1: use the transport frame sizes to calculate the max spp

The max send spp is the frame size minus the alignment padding.
This allows us to copy a remainder into a new buffer and always
commit multiples of the alignment size (512 bytes).

Reworked the managed send buffer implementation to handle the above.
Uses only managed memory, and only mem-copied under the alignment.

1 files changed, 2 insertions, 8 deletions

diff --git a/host/lib/usrp/usrp1/usrp1_impl.hpp b/host/lib/usrp/usrp1/usrp1_impl.hpp
index f2c464610..ff4d40762 100644
--- a/host/lib/usrp/usrp1/usrp1_impl.hpp
+++ b/host/lib/usrp/usrp1/usrp1_impl.hpp
@@ -90,15 +90,9 @@ public:
                 const uhd::io_type_t &,
                 recv_mode_t, double);
 
-    static const size_t BYTES_PER_PACKET = 512*4; //under the transfer size
+    size_t get_max_send_samps_per_packet(void) const;
 
-    size_t get_max_send_samps_per_packet(void) const {
-        return BYTES_PER_PACKET/_tx_otw_type.get_sample_size()/_tx_subdev_spec.size();
-    }
-
-    size_t get_max_recv_samps_per_packet(void) const {
-        return BYTES_PER_PACKET/_rx_otw_type.get_sample_size()/_rx_subdev_spec.size();
-    }
+    size_t get_max_recv_samps_per_packet(void) const;
 
     bool recv_async_msg(uhd::async_metadata_t &, double);