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SubjectRe: [PATCH v3 1/2] iommu - Enable debugfs exposure of the IOMMU
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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.hook@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?
^^^^^^^^^^^^^

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