staging: comedi: addi_apci_1500: Fix endian problem for command sample

BugLink: https://bugs.launchpad.net/bugs/1920246
commit ac0bbf55ed3be75fde1f8907e91ecd2fd589bde3 upstream.

The digital input subdevice supports Comedi asynchronous commands that
read interrupt status information.  This uses 16-bit Comedi samples (of
which only the bottom 8 bits contain status information).  However, the
interrupt handler is calling `comedi_buf_write_samples()` with the
address of a 32-bit variable `unsigned int status`.  On a bigendian
machine, this will copy 2 bytes from the wrong end of the variable.  Fix
it by changing the type of the variable to `unsigned short`.

Fixes: a8c66b684efa ("staging: comedi: addi_apci_1500: rewrite the subdevice support functions")
Cc: <stable@vger.kernel.org> #4.0+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20210223143055.257402-3-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

diff --git a/drivers/staging/comedi/drivers/addi_apci_1500.c b/drivers/staging/comedi/drivers/addi_apci_1500.c
index 816dd25b9d0e451d5312b762fd636be74e6ce067..8c3eff7cf465c1551a4840d971793a52457fc846 100644 (file)
--- a/drivers/staging/comedi/drivers/addi_apci_1500.c
+++ b/drivers/staging/comedi/drivers/addi_apci_1500.c
@@ -208,7 +208,7 @@ static irqreturn_t apci1500_interrupt(int irq, void *d)
        struct comedi_device *dev = d;
        struct apci1500_private *devpriv = dev->private;
        struct comedi_subdevice *s = dev->read_subdev;
-       unsigned int status = 0;
+       unsigned short status = 0;
        unsigned int val;
 
        val = inl(devpriv->amcc + AMCC_OP_REG_INTCSR);
@@ -238,14 +238,14 @@ static irqreturn_t apci1500_interrupt(int irq, void *d)
         *
         *    Mask     Meaning
         * ----------  ------------------------------------------
-        * 0x00000001  Event 1 has occurred
-        * 0x00000010  Event 2 has occurred
-        * 0x00000100  Counter/timer 1 has run down (not implemented)
-        * 0x00001000  Counter/timer 2 has run down (not implemented)
-        * 0x00010000  Counter 3 has run down (not implemented)
-        * 0x00100000  Watchdog has run down (not implemented)
-        * 0x01000000  Voltage error
-        * 0x10000000  Short-circuit error
+        * 0b00000001  Event 1 has occurred
+        * 0b00000010  Event 2 has occurred
+        * 0b00000100  Counter/timer 1 has run down (not implemented)
+        * 0b00001000  Counter/timer 2 has run down (not implemented)
+        * 0b00010000  Counter 3 has run down (not implemented)
+        * 0b00100000  Watchdog has run down (not implemented)
+        * 0b01000000  Voltage error
+        * 0b10000000  Short-circuit error
         */
        comedi_buf_write_samples(s, &status, 1);
        comedi_handle_events(dev, s);