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Subject[PATCH] staging: comedi: comedi_isadma: Use a non-NULL device for DMA API
Date
The "comedi_isadma" module calls `dma_alloc_coherent()` and
`dma_free_coherent()` with a NULL device pointer which is no longer
allowed. If the `hw_dev` member of the `struct comedi_device` has been
set to a valid device, that can be used instead. Unfortunately, all the
current users of the "comedi_isadma" module leave the `hw_dev` member
set to NULL. In that case, use a static dummy fallback device structure
with the coherent DMA mask set to the ISA bus limit of 16MB.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
---
drivers/staging/comedi/drivers/comedi_isadma.c | 15 +++++++++++++--
drivers/staging/comedi/drivers/comedi_isadma.h | 3 +++
2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/comedi/drivers/comedi_isadma.c b/drivers/staging/comedi/drivers/comedi_isadma.c
index b77dc8d5d3ff..8929952516a1 100644
--- a/drivers/staging/comedi/drivers/comedi_isadma.c
+++ b/drivers/staging/comedi/drivers/comedi_isadma.c
@@ -14,6 +14,16 @@

#include "comedi_isadma.h"

+/*
+ * Fallback device used when hardware device is NULL.
+ * This can be removed after drivers have been converted to use isa_driver.
+ */
+static struct device fallback_dev = {
+ .init_name = "comedi_isadma fallback device",
+ .coherent_dma_mask = DMA_BIT_MASK(24),
+ .dma_mask = &fallback_dev.coherent_dma_mask,
+};
+
/**
* comedi_isadma_program - program and enable an ISA DMA transfer
* @desc: the ISA DMA cookie to program and enable
@@ -172,6 +182,7 @@ struct comedi_isadma *comedi_isadma_alloc(struct comedi_device *dev,
goto no_dma;
dma->desc = desc;
dma->n_desc = n_desc;
+ dma->dev = dev->hw_dev ? dev->hw_dev : &fallback_dev;

dma_chans[0] = dma_chan1;
if (dma_chan2 == 0 || dma_chan2 == dma_chan1)
@@ -192,7 +203,7 @@ struct comedi_isadma *comedi_isadma_alloc(struct comedi_device *dev,
desc = &dma->desc[i];
desc->chan = dma_chans[i];
desc->maxsize = maxsize;
- desc->virt_addr = dma_alloc_coherent(NULL, desc->maxsize,
+ desc->virt_addr = dma_alloc_coherent(dma->dev, desc->maxsize,
&desc->hw_addr,
GFP_KERNEL);
if (!desc->virt_addr)
@@ -224,7 +235,7 @@ void comedi_isadma_free(struct comedi_isadma *dma)
for (i = 0; i < dma->n_desc; i++) {
desc = &dma->desc[i];
if (desc->virt_addr)
- dma_free_coherent(NULL, desc->maxsize,
+ dma_free_coherent(dma->dev, desc->maxsize,
desc->virt_addr,
desc->hw_addr);
}
diff --git a/drivers/staging/comedi/drivers/comedi_isadma.h b/drivers/staging/comedi/drivers/comedi_isadma.h
index 2bd1329d727f..9d2b12db7e6e 100644
--- a/drivers/staging/comedi/drivers/comedi_isadma.h
+++ b/drivers/staging/comedi/drivers/comedi_isadma.h
@@ -10,6 +10,7 @@
#include <linux/types.h>

struct comedi_device;
+struct device;

/*
* These are used to avoid issues when <asm/dma.h> and the DMA_MODE_
@@ -38,6 +39,7 @@ struct comedi_isadma_desc {

/**
* struct comedi_isadma - ISA DMA data
+ * @dev: device to allocate non-coherent memory for
* @desc: cookie for each DMA buffer
* @n_desc: the number of cookies
* @cur_dma: the current cookie in use
@@ -45,6 +47,7 @@ struct comedi_isadma_desc {
* @chan2: the second DMA channel requested
*/
struct comedi_isadma {
+ struct device *dev;
struct comedi_isadma_desc *desc;
int n_desc;
int cur_dma;
--
2.20.1
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