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staging: comedi: pcl818: fix pcl818_handle_dma() for short DMA transaction

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Currently this function always transfers the full DMA buffer to the comedi
async buffer. When the cmd->stop_src == TRIG_COUNT the last DMA transfer
might be smaller than the buffer size. This results in invalid data being
added to the asunc buffer.

Add a 'size' member to the DMA descriptor and initialize it with the
actual size of the DMA transfer. Use that in pcl818_handle_dma() to
return the proper number of samples. Use the comedi_bytes_to_samples()
helper to convert the byte size to comedi samples. Remove the unnecessary
'bufptr' local variable.

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>
This commit is contained in:
H Hartley Sweeten 2015-01-12 10:55:59 -07:00 committed by Greg Kroah-Hartman
parent 7a37b7a755
commit 1c53093a1d
1 changed files with 17 additions and 17 deletions
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34
drivers/staging/comedi/drivers/pcl818.c
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@ -305,6 +305,7 @@ static const struct pcl818_board boardtypes[] = {
struct pcl818_dma_desc {
void *virt_addr; /* virtual address of DMA buffer */
dma_addr_t hw_addr; /* hardware (bus) address of DMA buffer */
unsigned int size; /* transfer size (in bytes) */
};
struct pcl818_private {
@ -349,17 +350,17 @@ static void pcl818_ai_setup_dma(struct comedi_device *dev,
struct pcl818_dma_desc *dma = &devpriv->dma_desc[0];
struct comedi_cmd *cmd = &s->async->cmd;
unsigned int flags;
unsigned int bytes;
disable_dma(devpriv->dma); /* disable dma */
bytes = devpriv->hwdmasize;
if (cmd->stop_src == TRIG_COUNT) {
bytes = cmd->stop_arg * comedi_bytes_per_scan(s);
devpriv->dma_runs_to_end = bytes / devpriv->hwdmasize;
devpriv->last_dma_run = bytes % devpriv->hwdmasize;
dma->size = cmd->stop_arg * comedi_bytes_per_scan(s);
devpriv->dma_runs_to_end = dma->size / devpriv->hwdmasize;
devpriv->last_dma_run = dma->size % devpriv->hwdmasize;
devpriv->dma_runs_to_end--;
if (devpriv->dma_runs_to_end >= 0)
bytes = devpriv->hwdmasize;
dma->size = devpriv->hwdmasize;
} else {
dma->size = devpriv->hwdmasize;
}
devpriv->cur_dma = 0;
@ -367,7 +368,7 @@ static void pcl818_ai_setup_dma(struct comedi_device *dev,
flags = claim_dma_lock();
clear_dma_ff(devpriv->dma);
set_dma_addr(devpriv->dma, dma->hw_addr);
set_dma_count(devpriv->dma, bytes);
set_dma_count(devpriv->dma, dma->size);
release_dma_lock(flags);
enable_dma(devpriv->dma);
}
@ -385,13 +386,14 @@ static void pcl818_ai_setup_next_dma(struct comedi_device *dev,
if (devpriv->dma_runs_to_end > -1 || cmd->stop_src == TRIG_NONE) {
/* switch dma bufs */
dma = &devpriv->dma_desc[devpriv->cur_dma];
if (devpriv->dma_runs_to_end || cmd->stop_src == TRIG_NONE)
dma->size = devpriv->hwdmasize;
else
dma->size = devpriv->last_dma_run;
set_dma_mode(devpriv->dma, DMA_MODE_READ);
flags = claim_dma_lock();
set_dma_addr(devpriv->dma, dma->hw_addr);
if (devpriv->dma_runs_to_end || cmd->stop_src == TRIG_NONE)
set_dma_count(devpriv->dma, devpriv->hwdmasize);
else
set_dma_count(devpriv->dma, devpriv->last_dma_run);
set_dma_count(devpriv->dma, dma->size);
release_dma_lock(flags);
enable_dma(devpriv->dma);
}
@ -565,17 +567,15 @@ static void pcl818_handle_dma(struct comedi_device *dev,
struct pcl818_private *devpriv = dev->private;
struct pcl818_dma_desc *dma = &devpriv->dma_desc[devpriv->cur_dma];
unsigned short *ptr = dma->virt_addr;
unsigned int nsamples = comedi_bytes_to_samples(s, dma->size);
unsigned int chan;
unsigned int val;
int i, len, bufptr;
int i;
pcl818_ai_setup_next_dma(dev, s);
len = devpriv->hwdmasize >> 1;
bufptr = 0;
for (i = 0; i < len; i++) {
val = ptr[bufptr++];
for (i = 0; i < nsamples; i++) {
val = ptr[i];
chan = val & 0xf;
val = (val >> 4) & s->maxdata;