The following error can happen when trying to build it:
```
drivers/firmware/qcom_scm.c: In function ‘qcom_scm_assign_mem’:
drivers/firmware/qcom_scm.c:460:47: error: passing argument 3 of ‘dma_alloc_coherent’ from incompatible pointer type [-Werror=incompatible-pointer-types]
ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL);
^
In file included from drivers/firmware/qcom_scm.c:12:0:
./include/linux/dma-mapping.h:636:21: note: expected ‘dma_addr_t * {aka long long unsigned int *}’ but argument is of type ‘phys_addr_t * {aka unsigned int *}’
static inline void *dma_alloc_coherent(struct device *dev, size_t size,
^~~~~~~~~~~~~~~~~~
```
We just can cast phys_addr_t to dma_addr_t here.
Cc: Andy Gross <[email protected]>
Cc: David Brown <[email protected]>
Signed-off-by: Minwoo Im <[email protected]>
---
drivers/firmware/qcom_scm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index 2ddc118dba1b..7f6c841fa200 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -457,7 +457,8 @@ int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz,
ptr_sz = ALIGN(src_sz, SZ_64) + ALIGN(mem_to_map_sz, SZ_64) +
ALIGN(dest_sz, SZ_64);
- ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL);
+ ptr = dma_alloc_coherent(__scm->dev, ptr_sz, (dma_addr_t *) &ptr_phys,
+ GFP_KERNEL);
if (!ptr)
return -ENOMEM;
--
2.17.1
Adding people who have worked on drivers/firmware/qcom_scm.c or DMA
On 19/07/2019 15:43, Minwoo Im wrote:
> The following error can happen when trying to build it:
>
> ```
> drivers/firmware/qcom_scm.c: In function ‘qcom_scm_assign_mem’:
> drivers/firmware/qcom_scm.c:460:47: error: passing argument 3 of ‘dma_alloc_coherent’ from incompatible pointer type [-Werror=incompatible-pointer-types]
> ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL);
> ^
> In file included from drivers/firmware/qcom_scm.c:12:0:
> ./include/linux/dma-mapping.h:636:21: note: expected ‘dma_addr_t * {aka long long unsigned int *}’ but argument is of type ‘phys_addr_t * {aka unsigned int *}’
> static inline void *dma_alloc_coherent(struct device *dev, size_t size,
> ^~~~~~~~~~~~~~~~~~
> ```
>
> We just can cast phys_addr_t to dma_addr_t here.
IME, casting is rarely a proper solution.
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index 2ddc118dba1b..7f6c841fa200 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -457,7 +457,8 @@ int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz,
> ptr_sz = ALIGN(src_sz, SZ_64) + ALIGN(mem_to_map_sz, SZ_64) +
> ALIGN(dest_sz, SZ_64);
>
> - ptr = dma_alloc_coherent(__scm->dev, ptr_sz, &ptr_phys, GFP_KERNEL);
> + ptr = dma_alloc_coherent(__scm->dev, ptr_sz, (dma_addr_t *) &ptr_phys,
> + GFP_KERNEL);
> if (!ptr)
> return -ENOMEM;
>
On Mon, Jul 22, 2019 at 10:38:55AM +0200, Marc Gonzalez wrote:
> > In file included from drivers/firmware/qcom_scm.c:12:0:
> > ./include/linux/dma-mapping.h:636:21: note: expected ‘dma_addr_t * {aka long long unsigned int *}’ but argument is of type ‘phys_addr_t * {aka unsigned int *}’
> > static inline void *dma_alloc_coherent(struct device *dev, size_t size,
> > ^~~~~~~~~~~~~~~~~~
> > ```
> >
> > We just can cast phys_addr_t to dma_addr_t here.
>
> IME, casting is rarely a proper solution.
*nod*
ptr_phys probably should be a dma_addr_t. Unless this driver is so
magic that it really wants a physical and not a dma address, in which
case it needs to use alloc_pages instead of dma_alloc_coherent
and then call page_to_phys on the returned page, and a very big comment
explaining why it is so special.
On Mon 22 Jul 02:30 PDT 2019, Christoph Hellwig wrote:
> On Mon, Jul 22, 2019 at 10:38:55AM +0200, Marc Gonzalez wrote:
> > > In file included from drivers/firmware/qcom_scm.c:12:0:
> > > ./include/linux/dma-mapping.h:636:21: note: expected ?dma_addr_t * {aka long long unsigned int *}? but argument is of type ?phys_addr_t * {aka unsigned int *}?
> > > static inline void *dma_alloc_coherent(struct device *dev, size_t size,
> > > ^~~~~~~~~~~~~~~~~~
> > > ```
> > >
> > > We just can cast phys_addr_t to dma_addr_t here.
> >
> > IME, casting is rarely a proper solution.
>
> *nod*
>
> ptr_phys probably should be a dma_addr_t. Unless this driver is so
> magic that it really wants a physical and not a dma address, in which
> case it needs to use alloc_pages instead of dma_alloc_coherent
> and then call page_to_phys on the returned page, and a very big comment
> explaining why it is so special.
The scm call takes physical addresses (which happens to be 1:1 with DMA
addresses for this driver).
This allocation started off (downstream) as a simple kmalloc(), but
while the scm call is being executed an access from Linux will cause a
security violation (that's not handled gracefully). The properties of
dma_alloc is closer, so that's where the code is today.
Optimally this should be something like alloc_pages() and some mechanism
for unmapping the pages during the call. But no one has come up with a
suitable patch for that.
But there's a patch from Stephen for this already (not doing a
typecast). Apparently I missed merging this, so I'll do that.
https://lore.kernel.org/linux-arm-msm/[email protected]/
Regards,
Bjorn
> > > > We just can cast phys_addr_t to dma_addr_t here.
> > >
> > > IME, casting is rarely a proper solution.
> >
> > *nod*
> >
> > ptr_phys probably should be a dma_addr_t. Unless this driver is so
> > magic that it really wants a physical and not a dma address, in which
> > case it needs to use alloc_pages instead of dma_alloc_coherent
> > and then call page_to_phys on the returned page, and a very big comment
> > explaining why it is so special.
>
> The scm call takes physical addresses (which happens to be 1:1 with DMA
> addresses for this driver).
>
> This allocation started off (downstream) as a simple kmalloc(), but
> while the scm call is being executed an access from Linux will cause a
> security violation (that's not handled gracefully). The properties of
> dma_alloc is closer, so that's where the code is today.
>
> Optimally this should be something like alloc_pages() and some mechanism
> for unmapping the pages during the call. But no one has come up with a
> suitable patch for that.
>
>
> But there's a patch from Stephen for this already (not doing a
> typecast). Apparently I missed merging this, so I'll do that.
>
> https://lore.kernel.org/linux-arm-msm/[email protected]/
Bjron,
I appreciate for checking this. And also thanks all you guys for the
comments here!
Thanks,