staging: comedi: addi_apci_3120: prevent deadlock in apci3120_ao_insn_write()

The DA_READY bit (0x0001) in the status register needs to be set before the
analog outputs can be updated.

Use comedi_timeout() to prevent a deadlock condition while waiting for the
DA_READY bit to get set.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/addi-data/hwdrv_apci3120.c b/drivers/staging/comedi/drivers/addi-data/hwdrv_apci3120.c
index 0ba4b79..b6c11fe 100644 (file)
--- a/drivers/staging/comedi/drivers/addi-data/hwdrv_apci3120.c
+++ b/drivers/staging/comedi/drivers/addi-data/hwdrv_apci3120.c
@@ -1923,21 +1923,34 @@ static int apci3120_do_insn_bits(struct comedi_device *dev,
        return insn->n;
 }
 
+static int apci3120_ao_ready(struct comedi_device *dev,
+                            struct comedi_subdevice *s,
+                            struct comedi_insn *insn,
+                            unsigned long context)
+{
+       unsigned int status;
+
+       status = inw(dev->iobase + APCI3120_RD_STATUS);
+       if (status & 0x0001)    /* waiting for DA_READY */
+               return 0;
+       return -EBUSY;
+}
+
 static int apci3120_ao_insn_write(struct comedi_device *dev,
                                  struct comedi_subdevice *s,
                                  struct comedi_insn *insn,
                                  unsigned int *data)
 {
        unsigned int ui_Channel;
-       unsigned short us_TmpValue;
+       int ret;
 
        ui_Channel = CR_CHAN(insn->chanspec);
 
        data[0] = ((((ui_Channel & 0x03) << 14) & 0xC000) | data[0]);
 
-       do {                    /* Waiting of DA_READY BIT */
-               us_TmpValue = inw(dev->iobase + APCI3120_RD_STATUS) & 0x0001;
-       } while (us_TmpValue != 0x0001);
+       ret = comedi_timeout(dev, s, insn, apci3120_ao_ready, 0);
+       if (ret)
+               return ret;
 
        if (ui_Channel <= 3)
                /*