trying to clarify interrupt logic a little

diff --git a/comedi/drivers/das16.c b/comedi/drivers/das16.c
index 60ab43d55b8b1d3026b9feed3d22f3db808a6854..ea9a31eaef171f0bfe8195080c397dca4e65c40c 100644 (file)
--- a/comedi/drivers/das16.c
+++ b/comedi/drivers/das16.c
@@ -717,7 +717,8 @@ struct das16_private_struct {
        unsigned int divisor2;  // divisor dividing master clock to get conversion frequency
        unsigned int dma_chan;  // dma channel
        sampl_t *dma_buffer;
-       volatile unsigned int dma_transfer_size;        // number of bytes transfered per dma shot
+       volatile unsigned int target_transfer_size;     // target number of bytes to transfer per dma shot
+       volatile unsigned int actual_transfer_size;     // number of bytes in current dma transfer
        // user-defined analog input and output ranges defined from config options
        comedi_lrange *user_ai_range_table;
        comedi_lrange *user_ao_range_table;
@@ -950,8 +951,9 @@ static int das16_cmd_exec(comedi_device *dev,comedi_subdevice *s)
        clear_dma_ff(devpriv->dma_chan);
        set_dma_addr(devpriv->dma_chan, virt_to_bus(devpriv->dma_buffer));
        // set appropriate size of transfer
-       devpriv->dma_transfer_size = das16_suggest_transfer_size(dev, *cmd);
-       set_dma_count(devpriv->dma_chan, devpriv->dma_transfer_size);
+       devpriv->target_transfer_size = das16_suggest_transfer_size(dev, *cmd);
+       devpriv->actual_transfer_size = devpriv->target_transfer_size;
+       set_dma_count(devpriv->dma_chan, devpriv->actual_transfer_size);
        enable_dma(devpriv->dma_chan);
        release_dma_lock(flags);
 
@@ -1157,8 +1159,9 @@ static void das16_interrupt( comedi_device *dev )
        comedi_subdevice *s = dev->read_subdev;
        comedi_async *async;
        comedi_cmd *cmd;
-       int num_points, num_bytes, residue, next_num_bytes;
+       int num_points, num_bytes, residue;
        sampl_t dpnt;
+       unsigned int target_xfer;
 
        if(dev->attached == 0)
        {
@@ -1183,13 +1186,13 @@ static void das16_interrupt( comedi_device *dev )
         * the stop_src is set to external triggering.
         */
        residue = get_dma_residue(devpriv->dma_chan);
-       if(residue > devpriv->dma_transfer_size)
+       if(residue > devpriv->actual_transfer_size)
        {
                comedi_error(dev, "residue > transfer size!\n");
                async->events |= COMEDI_CB_ERROR | COMEDI_CB_EOA;
                num_bytes = 0;
        }else
-               num_bytes = devpriv->dma_transfer_size - residue;
+               num_bytes = devpriv->actual_transfer_size + devpriv->remains - residue;
        num_points = num_bytes / sample_size;
        devpriv->remains = num_bytes % sample_size;
 
@@ -1211,10 +1214,12 @@ static void das16_interrupt( comedi_device *dev )
        }
 
        // figure out how many bytes for next transfer
-       next_num_bytes = devpriv->dma_transfer_size - devpriv->remains;
+       target_xfer = devpriv->target_transfer_size;
        if(cmd->stop_src == TRIG_COUNT && devpriv->timer_mode == 0 &&
-               next_num_bytes + devpriv->remains > devpriv->adc_count * sample_size)
-               next_num_bytes = devpriv->adc_count * sample_size - devpriv->remains;
+               target_xfer > devpriv->adc_count * sample_size)
+               target_xfer = devpriv->adc_count * sample_size;
+
+       devpriv->actual_transfer_size = target_xfer - devpriv->remains;
 
        // re-enable  dma
        if(( async->events & COMEDI_CB_EOA ) == 0)
@@ -1222,7 +1227,7 @@ static void das16_interrupt( comedi_device *dev )
                // copy possible leftover byte to beginning of buffer to be read next time
                devpriv->dma_buffer[0] = devpriv->dma_buffer[num_points];
                set_dma_addr(devpriv->dma_chan, virt_to_bus(devpriv->dma_buffer) + devpriv->remains);
-               set_dma_count(devpriv->dma_chan, next_num_bytes);
+               set_dma_count(devpriv->dma_chan, devpriv->actual_transfer_size);
                enable_dma(devpriv->dma_chan);
        }
        release_dma_lock(flags);