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Commit 1c53093a authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
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staging: comedi: pcl818: fix pcl818_handle_dma() for short DMA transaction 



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: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7a37b7a7

drivers/staging/comedi/drivers/pcl818.c

+17 −17
Original line number Diff line number Diff line
@@ -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;