On Tue, Sep 27, 2011 at 3:56 AM, KyongHo Cho <pullip.cho@xxxxxxxxxxx> wrote:
> I wanted the IOMMU driver to provide default fault handler to its users
> that does not provide fault handler for debugging purpose.
> If a user want to handle MMU fault, IOMMU driver welcomes to overwrite
> the existing 'default' fault handler.
Ok, this one patch below should allow you to do that.
report_iommu_fault() will now reliably tell you if a fault handler
failed or not, or if one isn't even installed.
This way your IOMMU driver doesn't need to define a fault handler of
its own, and instead, can do everything directly in
exynos_sysmmu_irq() where all the required information is now
available.
Thanks,
Ohad.
>From 0f2287abe5761e40d25f0da0c8e7964d18ebb3ef Mon Sep 17 00:00:00 2001
From: Ohad Ben-Cohen <ohad@xxxxxxxxxx>
Date: Tue, 27 Sep 2011 11:14:22 +0300
Subject: [PATCH] iommu/core: let drivers know if an iommu fault
handler isn't installed
Let report_iommu_fault() return -ENOSYS whenever an iommu fault
handler isn't installed, so IOMMU drivers can then do their own
platform-specific default behavior if they want.
Clarify that -ENOSYS is reserved for this purpose, and that fault
handlers are prohibited from using it.
Signed-off-by: Ohad Ben-Cohen <ohad@xxxxxxxxxx>
---
drivers/iommu/iommu.c | 7 +++++++
include/linux/iommu.h | 3 ++-
2 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3a07259..c41a6a1 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -43,6 +43,13 @@ EXPORT_SYMBOL_GPL(iommu_found);
* iommu_set_fault_handler() - set a fault handler for an iommu domain
* @domain: iommu domain
* @handler: fault handler
+ *
+ * This function should be used by IOMMU users which want to be notified
+ * whenever an IOMMU fault happens.
+ *
+ * The fault handler itself should return 0 on success, and an appropriate
+ * error code otherwise. It should never return -ENOSYS though, as this is
+ * reserved for the IOMMU core to return when no handler is installed.
*/
void iommu_set_fault_handler(struct iommu_domain *domain,
iommu_fault_handler_t handler)
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index d084e87..2987199 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -98,11 +98,12 @@ extern void iommu_set_fault_handler(struct
iommu_domain *domain,
* Returns 0 on success and an appropriate error code otherwise (if dynamic
* PTE/TLB loading will one day be supported, implementations will be able
* to tell whether it succeeded or not according to this return value).
+ * If a fault handler isn't installed, -ENOSYS is returned.
*/
static inline int report_iommu_fault(struct iommu_domain *domain,
struct device *dev, unsigned long iova, int flags)
{
- int ret = 0;
+ int ret = -ENOSYS;
/*
* if upper layers showed interest and installed a fault handler,
--
1.7.4.1
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