staging: comedi: ni_65xx: Use 16-bit 0 for interrupt data

The ni_65xx driver has an "interrupt" subdevice that supports Comedi
asynchronous commands, placing a value in the Comedi buffer for each
interrupt.  The subdevice uses Comedi's 16-bit sample format but the
interrupt handler is calling `comedi_buf_write_samples()` with the
address of a 32-bit integer `&s->state`.  On bigendian machines, this
will copy 2 bytes from the wrong end of the 32-bit integer.  This isn't
really a problem since `s->state` will always be 0 for this subdevice,
but clean it up by using a 16-bit variable initialized to 0 to pass the
value.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20210223143055.257402-14-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/ni_65xx.c b/drivers/staging/comedi/drivers/ni_65xx.c
index eb3f9f7..7cd8497 100644 (file)
--- a/drivers/staging/comedi/drivers/ni_65xx.c
+++ b/drivers/staging/comedi/drivers/ni_65xx.c
@@ -472,6 +472,7 @@ static irqreturn_t ni_65xx_interrupt(int irq, void *d)
        struct comedi_device *dev = d;
        struct comedi_subdevice *s = dev->read_subdev;
        unsigned int status;
+       unsigned short val = 0;
 
        status = readb(dev->mmio + NI_65XX_STATUS_REG);
        if ((status & NI_65XX_STATUS_INT) == 0)
@@ -482,7 +483,7 @@ static irqreturn_t ni_65xx_interrupt(int irq, void *d)
        writeb(NI_65XX_CLR_EDGE_INT | NI_65XX_CLR_OVERFLOW_INT,
               dev->mmio + NI_65XX_CLR_REG);
 
-       comedi_buf_write_samples(s, &s->state, 1);
+       comedi_buf_write_samples(s, &val, 1);
        comedi_handle_events(dev, s);
 
        return IRQ_HANDLED;