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    SubjectRe: [PATCH/RFCv4 3/6] mm: cma: Added SysFS support
    On Fri, Aug 20, 2010 at 11:50:43AM +0200, Michal Nazarewicz wrote:
    > The SysFS development interface lets one change the map attribute
    > at run time as well as observe what regions have been reserved.
    >
    > Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
    > Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
    > ---
    > .../ABI/testing/sysfs-kernel-mm-contiguous | 53 +++
    > Documentation/contiguous-memory.txt | 4 +
    > include/linux/cma.h | 7 +
    > mm/Kconfig | 18 +-
    > mm/cma.c | 345 +++++++++++++++++++-
    > 5 files changed, 423 insertions(+), 4 deletions(-)
    > create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-contiguous
    >
    > diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-contiguous b/Documentation/ABI/testing/sysfs-kernel-mm-contiguous
    > new file mode 100644
    > index 0000000..8df15bc
    > --- /dev/null
    > +++ b/Documentation/ABI/testing/sysfs-kernel-mm-contiguous
    > @@ -0,0 +1,53 @@
    > +What: /sys/kernel/mm/contiguous/
    > +Date: August 2010
    > +Contact: Michal Nazarewicz <m.nazarewicz@samsung.com>
    > +Description:
    > + If CMA has been built with SysFS support,
    > + /sys/kernel/mm/contiguous/ contains a file called
    > + "map", a file called "allocators" and a directory
    > + called "regions".
    > +
    > + The "map" file lets one change the CMA's map attribute
    > + at run-time.
    > +
    > + The "allocators" file list all registered allocators.
    > + Allocators with no name are listed as a single minus
    > + sign.
    > +
    > + The "regions" directory list all reserved regions.
    > +
    > + For more details see
    > + Documentation/contiguous-memory.txt.
    > +
    > +What: /sys/kernel/mm/contiguous/regions/
    > +Date: August 2010
    > +Contact: Michal Nazarewicz <m.nazarewicz@samsung.com>
    > +Description:
    > + The /sys/kernel/mm/contiguous/regions/ directory
    > + contain directories for each registered CMA region.
    > + The name of the directory is the same as the start
    > + address of the region.
    > +
    > + If region is named there is also a symbolic link named
    > + like the region pointing to the region's directory.
    > +
    > + Such directory contains the following files:
    > +
    > + * "name" -- the name of the region or an empty file
    > + * "start" -- starting address of the region (formatted
    > + with %p, ie. hex).
    > + * "size" -- size of the region (in bytes).
    > + * "free" -- free space in the region (in bytes).
    > + * "users" -- number of chunks allocated in the region.
    > + * "alloc" -- name of the allocator.
    > +
    > + If allocator is not attached to the region, "alloc" is
    > + either the name of desired allocator in square
    > + brackets (ie. "[foo]") or an empty file if region is
    > + to be attached to default allocator. If an allocator
    > + is attached to the region. "alloc" is either its name
    > + or "-" if attached allocator has no name.
    > +
    > + If there are no chunks allocated in given region
    > + ("users" is "0") then a name of desired allocator can
    > + be written to "alloc".
    > diff --git a/Documentation/contiguous-memory.txt b/Documentation/contiguous-memory.txt
    > index 8fc2400..8d189b8 100644
    > --- a/Documentation/contiguous-memory.txt
    > +++ b/Documentation/contiguous-memory.txt
    > @@ -256,6 +256,10 @@
    > iff it matched in previous pattern. If the second part is
    > omitted it will mach any type of memory requested by device.
    >
    > + If SysFS support is enabled, this attribute is accessible via
    > + SysFS and can be changed at run-time by writing to
    > + /sys/kernel/mm/contiguous/map.
    > +
    > Some examples (whitespace added for better readability):
    >
    > cma_map = foo/quaz = r1;
    > diff --git a/include/linux/cma.h b/include/linux/cma.h
    > index cd63f52..eede28d 100644
    > --- a/include/linux/cma.h
    > +++ b/include/linux/cma.h
    > @@ -17,6 +17,9 @@
    >
    > #include <linux/rbtree.h>
    > #include <linux/list.h>
    > +#if defined CONFIG_CMA_SYSFS
    > +# include <linux/kobject.h>
    > +#endif
    >
    >
    > struct device;
    > @@ -203,6 +206,10 @@ struct cma_region {
    > unsigned users;
    > struct list_head list;
    >
    > +#if defined CONFIG_CMA_SYSFS
    > + struct kobject kobj;
    > +#endif
    > +
    > unsigned used:1;
    > unsigned registered:1;
    > unsigned reserved:1;
    > diff --git a/mm/Kconfig b/mm/Kconfig
    > index 3e9317c..ac0bb08 100644
    > --- a/mm/Kconfig
    > +++ b/mm/Kconfig
    > @@ -319,12 +319,26 @@ config CMA
    > To make use of CMA you need to specify the regions and
    > driver->region mapping on command line when booting the kernel.
    >
    > -config CMA_DEBUG
    > - bool "CMA debug messages (DEVELOPEMENT)"
    > +config CMA_DEVELOPEMENT
    > + bool "Include CMA developement features"
    > depends on CMA
    > help
    > + This lets you enable some developement features of the CMA
    > + freamework.
    > +
    > +config CMA_DEBUG
    > + bool "CMA debug messages"
    > + depends on CMA_DEVELOPEMENT
    > + help
    > Enable debug messages in CMA code.
    >
    > +config CMA_SYSFS
    > + bool "CMA SysFS interface support"
    > + depends on CMA_DEVELOPEMENT
    > + help
    > + Enable support for SysFS interface.

    Whats the rationale for having those #ifdef CONFIG_CMA_SYSFS sprinkled
    in the C code? Is SysFS not used on StrongARM? Why not implicitly include
    the SysFS support?



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