On 25/04/2019 18:13, Greg Kroah-Hartman wrote:
On Thu, Apr 25, 2019 at 05:26:44PM +0100, Ian Abbott wrote:
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@xxxxxxxxx>
---
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,
+};
Ick, no, static struct device are a very bad idea as this is a reference
counted structure and making it static can cause odd problems.
This was based on the use of `struct device x86_dma_fallback_dev` in
"arch/x86/kernel/pci-dma.c", and `static struct device isa_dma_dev` in
"arch/arm/kernel/dma-isa.c", but perhaps it is not appropriate in
non-arch code.
Why not just create a "real" one? Or better yet, use the real device
for the comedi device as all of these drivers should have one now.
I suppose I could use the comedi class device pointed to by the
`class_dev` member of `struct comedi_device` (although that could also
be NULL because the comedi core does not currently treat
`device_create()` failures as fatal).
thanks,
greg k-h
Thanks for the review,
Ian Abbott.
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