staging: comedi: store the 'index' for each subdevice

Store the 'index' for each comedi_subdevice when they are initially
allocated by comedi_alloc_subdevice(). This allows removing the
pointer math in comedi_fops.c which is used to figure out the
index that user space uses to access the individual subdevices.

Fix the ni_mio_common driver so it also uses the 'index' instead
of doing the pointer math.

Also, remove a couple unused macros in the pcmda12, pcmmio, and
pcmuio drivers which also do the pointer math to figure out the
index.

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

drivers/staging/comedi/comedi_fops.c

@@ -169,7 +169,7 @@ static int resize_async_buffer(struct comedi_device *dev,
 	}
 
 	DPRINTK("comedi%i subd %d buffer resized to %i bytes\n",
-		dev->minor, (int)(s - dev->subdevices), async->prealloc_bufsz);
+		dev->minor, s->index, async->prealloc_bufsz);
 	return 0;
 }
 
@@ -624,13 +624,13 @@ static int do_devinfo_ioctl(struct comedi_device *dev,
 
 	s = comedi_read_subdevice(info);
 	if (s)
-		devinfo.read_subdevice = s - dev->subdevices;
+		devinfo.read_subdevice = s->index;
 	else
 		devinfo.read_subdevice = -1;
 
 	s = comedi_write_subdevice(info);
 	if (s)
-		devinfo.write_subdevice = s - dev->subdevices;
+		devinfo.write_subdevice = s->index;
 	else
 		devinfo.write_subdevice = -1;
 
@@ -2398,7 +2398,7 @@ int comedi_alloc_subdevice_minor(struct comedi_device *dev,
 	s->minor = i;
 	csdev = device_create(comedi_class, dev->class_dev,
 			      MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i_subd%i",
-			      dev->minor, (int)(s - dev->subdevices));
+			      dev->minor, s->index);
 	if (!IS_ERR(csdev))
 		s->class_dev = csdev;
 	dev_set_drvdata(csdev, info);

drivers/staging/comedi/comedidev.h

@@ -77,6 +77,7 @@
 
 struct comedi_subdevice {
 	struct comedi_device *device;
+	int index;
 	int type;
 	int n_chan;
 	int subdev_flags;

drivers/staging/comedi/drivers.c

@@ -70,6 +70,7 @@ int comedi_alloc_subdevices(struct comedi_device *dev, int num_subdevices)
 	for (i = 0; i < num_subdevices; ++i) {
 		s = &dev->subdevices[i];
 		s->device = dev;
+		s->index = i;
 		s->async_dma_dir = DMA_NONE;
 		spin_lock_init(&s->spin_lock);
 		s->minor = -1;

drivers/staging/comedi/drivers/ni_mio_common.c

@@ -986,7 +986,7 @@ static void ni_event(struct comedi_device *dev, struct comedi_subdevice *s)
 	if (s->
 	    async->events & (COMEDI_CB_ERROR | COMEDI_CB_OVERFLOW |
 			     COMEDI_CB_EOA)) {
-		switch (s - dev->subdevices) {
+		switch (s->index) {
 		case NI_AI_SUBDEV:
 			ni_ai_reset(dev, s);
 			break;

drivers/staging/comedi/drivers/pcmda12.c

@@ -55,7 +55,6 @@ Configuration Options:
 
 #include <linux/pci.h>		/* for PCI devices */
 
-#define SDEV_NO ((int)(s - dev->subdevices))
 #define CHANS 8
 #define IOSIZE 16
 #define LSB(x) ((unsigned char)((x) & 0xff))

drivers/staging/comedi/drivers/pcmmio.c

@@ -94,7 +94,6 @@ Configuration Options:
 #define INTR_PORTS_PER_SUBDEV (INTR_CHANS_PER_ASIC/CHANS_PER_PORT)
 #define MAX_DIO_CHANS   (PORTS_PER_ASIC*1*CHANS_PER_PORT)
 #define MAX_ASICS       (MAX_DIO_CHANS/CHANS_PER_ASIC)
-#define SDEV_NO ((int)(s - dev->subdevices))
 #define CALC_N_DIO_SUBDEVS(nchans) ((nchans)/MAX_CHANS_PER_SUBDEV + (!!((nchans)%MAX_CHANS_PER_SUBDEV)) /*+ (nchans > INTR_CHANS_PER_ASIC ? 2 : 1)*/)
 /* IO Memory sizes */
 #define ASIC_IOSIZE (0x0B)

drivers/staging/comedi/drivers/pcmuio.c

@@ -92,7 +92,6 @@ Configuration Options:
 #define INTR_PORTS_PER_SUBDEV (INTR_CHANS_PER_ASIC/CHANS_PER_PORT)
 #define MAX_DIO_CHANS   (PORTS_PER_ASIC*2*CHANS_PER_PORT)
 #define MAX_ASICS       (MAX_DIO_CHANS/CHANS_PER_ASIC)
-#define SDEV_NO ((int)(s - dev->subdevices))
 #define CALC_N_SUBDEVS(nchans) ((nchans)/MAX_CHANS_PER_SUBDEV + (!!((nchans)%MAX_CHANS_PER_SUBDEV)) /*+ (nchans > INTR_CHANS_PER_ASIC ? 2 : 1)*/)
 /* IO Memory sizes */
 #define ASIC_IOSIZE (0x10)