On 17/04/18 18:46, Hook, Gary wrote:
On 4/6/2018 9:17 AM, Gary R Hook wrote:
Provide base enablement for using debugfs to expose internal data of
an IOMMU driver. When called, create the /sys/kernel/debug/iommu
directory. Emit a strong warning at boot time to indicate that this
feature is enabled.
This patch adds a top-level function that will create the (above)
directory, under which a driver may create a hw-specific directory for
its use. The function
iommu_debugfs_setup()
returns a pointer to the new dentry structure created for
/sys/kernel/debug/iommu, or NULL in the event of a failure. An IOMMU
driver should call this function first, and then create a directory
beneath it. A driver implementation might look something like:
static struct dentry *my_debugfs;
struct dentry *d_top;
if (!my_debugfs) {
d_top = iommu_debugfs_setup();
if (d_top)
my_debugfs = debugfs_create_dir("vendor", d_top);
}
Since the IOMMU driver can not be removed from the running system, this
patch only provides an "on" function.
Signed-off-by: Gary R Hook <gary.h...@amd.com>
---
drivers/iommu/Kconfig | 11 ++++++++
drivers/iommu/Makefile | 1 +
drivers/iommu/iommu-debugfs.c | 58
+++++++++++++++++++++++++++++++++++++++++
include/linux/iommu.h | 4 +++
4 files changed, 74 insertions(+)
create mode 100644 drivers/iommu/iommu-debugfs.c
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index f3a21343e636..c1e39dabfec2 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -60,6 +60,17 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST
endmenu
+config IOMMU_DEBUG
+ bool "Enable IOMMU internals in DebugFS"
+ depends on DEBUG_FS
+ default n
+ help
+ Allows exposure of IOMMU device internals. This option enables
+ the use of debugfs by IOMMU drivers as required. Devices can,
+ at initialization time, cause the IOMMU code to create a top-level
+ debug/iommu directory, and then populate a subdirectory with
+ entries as required.
I should explicitly ask about this:
Joerg had suggested IOMMU_DEBUGFS, but here I've changed to IOMMU_DEBUG.
I'm not seeing a lot of CONFIG options that use DEBUGFS for debugfs
options, so I chose to follow an implied convention.
Question: should this indeed be IOMMU_DEBUGFS?
^^^^^^^^^^^^^
Personally I'd say yes, since there is at least some precedent for
*_DEBUGFS already, and it does help make the intent that much clearer
(*_DEBUG often just means lots of dmesg spam rather than an actual
debugfs interface).
Robin.
