staging: comedi: adl_pci9118: tidy up pci9118_ai_setup_dma()

For aesthetics, init the dmalen[01] local variables when they are declared.

Use a local variable, 'scan_bytes', for the (devpriv->ai_n_realscanlen << 1)
calculation. For aesthetics and clarification, use comedi_bytes_per_sample()
instead of the '<< 1' shift to calculate the value.

The local variable 'i' is badly named. Remove it and use a local variable
'tmp' where it is used.

When checking the DMA buffer lengths for non-neverending commands the
scan length calculation, (devpriv->ai_n_realscanlen << 1) * cmd->stop_arg,
could overflow. Use and unsigned long long local variable to hold the
calculation and avoid the overflow.

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/adl_pci9118.c b/drivers/staging/comedi/drivers/adl_pci9118.c
index e2302cb..0dff1db 100644 (file)
--- a/drivers/staging/comedi/drivers/adl_pci9118.c
+++ b/drivers/staging/comedi/drivers/adl_pci9118.c
@@ -801,10 +801,11 @@ static int pci9118_ai_setup_dma(struct comedi_device *dev,
        struct comedi_cmd *cmd = &s->async->cmd;
        struct pci9118_dmabuf *dmabuf0 = &devpriv->dmabuf[0];
        struct pci9118_dmabuf *dmabuf1 = &devpriv->dmabuf[1];
-       unsigned int dmalen0, dmalen1, i;
+       unsigned int dmalen0 = dmabuf0->size;
+       unsigned int dmalen1 = dmabuf1->size;
+       unsigned int scan_bytes = devpriv->ai_n_realscanlen *
+                                 comedi_bytes_per_sample(s);
 
-       dmalen0 = dmabuf0->size;
-       dmalen1 = dmabuf1->size;
        /* isn't output buff smaller that our DMA buff? */
        if (dmalen0 > s->async->prealloc_bufsz) {
                /* align to 32bit down */
@@ -817,15 +818,15 @@ static int pci9118_ai_setup_dma(struct comedi_device *dev,
 
        /* we want wake up every scan? */
        if (devpriv->ai_flags & CMDF_WAKE_EOS) {
-               if (dmalen0 < (devpriv->ai_n_realscanlen << 1)) {
+               if (dmalen0 < scan_bytes) {
                        /* uff, too short DMA buffer, disable EOS support! */
                        devpriv->ai_flags &= (~CMDF_WAKE_EOS);
                        dev_info(dev->class_dev,
                                 "WAR: DMA0 buf too short, can't support CMDF_WAKE_EOS (%d<%d)\n",
-                                 dmalen0, devpriv->ai_n_realscanlen << 1);
+                                 dmalen0, scan_bytes);
                } else {
                        /* short first DMA buffer to one scan */
-                       dmalen0 = devpriv->ai_n_realscanlen << 1;
+                       dmalen0 = scan_bytes;
                        if (dmalen0 < 4) {
                                dev_info(dev->class_dev,
                                         "ERR: DMA0 buf len bug? (%d<4)\n",
@@ -835,15 +836,15 @@ static int pci9118_ai_setup_dma(struct comedi_device *dev,
                }
        }
        if (devpriv->ai_flags & CMDF_WAKE_EOS) {
-               if (dmalen1 < (devpriv->ai_n_realscanlen << 1)) {
+               if (dmalen1 < scan_bytes) {
                        /* uff, too short DMA buffer, disable EOS support! */
                        devpriv->ai_flags &= (~CMDF_WAKE_EOS);
                        dev_info(dev->class_dev,
                                 "WAR: DMA1 buf too short, can't support CMDF_WAKE_EOS (%d<%d)\n",
-                                dmalen1, devpriv->ai_n_realscanlen << 1);
+                                dmalen1, scan_bytes);
                } else {
                        /* short second DMA buffer to one scan */
-                       dmalen1 = devpriv->ai_n_realscanlen << 1;
+                       dmalen1 = scan_bytes;
                        if (dmalen1 < 4) {
                                dev_info(dev->class_dev,
                                         "ERR: DMA1 buf len bug? (%d<4)\n",
@@ -855,45 +856,39 @@ static int pci9118_ai_setup_dma(struct comedi_device *dev,
 
        /* transfer without CMDF_WAKE_EOS */
        if (!(devpriv->ai_flags & CMDF_WAKE_EOS)) {
+               unsigned int tmp;
+
                /* if it's possible then align DMA buffers to length of scan */
-               i = dmalen0;
-               dmalen0 =
-                   (dmalen0 / (devpriv->ai_n_realscanlen << 1)) *
-                   (devpriv->ai_n_realscanlen << 1);
+               tmp = dmalen0;
+               dmalen0 = (dmalen0 / scan_bytes) * scan_bytes;
                dmalen0 &= ~3L;
                if (!dmalen0)
-                       dmalen0 = i;    /* uff. very long scan? */
-               i = dmalen1;
-               dmalen1 =
-                   (dmalen1 / (devpriv->ai_n_realscanlen << 1)) *
-                   (devpriv->ai_n_realscanlen << 1);
+                       dmalen0 = tmp;  /* uff. very long scan? */
+               tmp = dmalen1;
+               dmalen1 = (dmalen1 / scan_bytes) * scan_bytes;
                dmalen1 &= ~3L;
                if (!dmalen1)
-                       dmalen1 = i;    /* uff. very long scan? */
+                       dmalen1 = tmp;  /* uff. very long scan? */
                /*
                 * if measure isn't neverending then test, if it fits whole
                 * into one or two DMA buffers
                 */
                if (!devpriv->ai_neverending) {
+                       unsigned long long scanlen;
+
+                       scanlen = (unsigned long long)scan_bytes *
+                                 cmd->stop_arg;
+
                        /* fits whole measure into one DMA buffer? */
-                       if (dmalen0 >
-                           ((devpriv->ai_n_realscanlen << 1) *
-                            cmd->stop_arg)) {
-                               dmalen0 =
-                                   (devpriv->ai_n_realscanlen << 1) *
-                                   cmd->stop_arg;
+                       if (dmalen0 > scanlen) {
+                               dmalen0 = scanlen;
                                dmalen0 &= ~3L;
-                       } else {        /*
-                                        * fits whole measure into
-                                        * two DMA buffer?
-                                        */
-                               if (dmalen1 >
-                                   ((devpriv->ai_n_realscanlen << 1) *
-                                    cmd->stop_arg - dmalen0))
-                                       dmalen1 =
-                                           (devpriv->ai_n_realscanlen << 1) *
-                                           cmd->stop_arg - dmalen0;
-                               dmalen1 &= ~3L;
+                       } else {
+                               /* fits whole measure into two DMA buffer? */
+                               if (dmalen1 > (scanlen - dmalen0)) {
+                                       dmalen1 = scanlen - dmalen0;
+                                       dmalen1 &= ~3L;
+                               }
                        }
                }
        }