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author | Jacob Keller <jacob.e.keller@intel.com> | 2022-11-28 23:36:44 +0300 |
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committer | Jakub Kicinski <kuba@kernel.org> | 2022-12-01 07:54:30 +0300 |
commit | af6397c9ee2b42988c912dcad2fca1f43d5c1c99 (patch) | |
tree | e03db8f360ad11aabc59a99489d9fb683c9d5915 /Documentation/networking | |
parent | 2d4caf0988bd3e9663c300e95cead91f2f954fae (diff) | |
download | linux-af6397c9ee2b42988c912dcad2fca1f43d5c1c99.tar.xz |
devlink: support directly reading from region memory
To read from a region, user space must currently request a new snapshot of
the region and then read from that snapshot. This can sometimes be overkill
if user space only reads a tiny portion. They first create the snapshot,
then request a read, then destroy the snapshot.
For regions which have a single underlying "contents", it makes sense to
allow supporting direct reading of the region data.
Extend the DEVLINK_CMD_REGION_READ to allow direct reading from a region if
requested via the new DEVLINK_ATTR_REGION_DIRECT. If this attribute is set,
then perform a direct read instead of using a snapshot. Direct read is
mutually exclusive with DEVLINK_ATTR_REGION_SNAPSHOT_ID, and care is taken
to ensure that we reject commands which provide incorrect attributes.
Regions must enable support for direct read by implementing the .read()
callback function. If a region does not support such direct reads, a
suitable extended error message is reported.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'Documentation/networking')
-rw-r--r-- | Documentation/networking/devlink/devlink-region.rst | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/networking/devlink/devlink-region.rst b/Documentation/networking/devlink/devlink-region.rst index f06dca9a1eb6..9232cd7da301 100644 --- a/Documentation/networking/devlink/devlink-region.rst +++ b/Documentation/networking/devlink/devlink-region.rst @@ -31,6 +31,15 @@ in its ``devlink_region_ops`` structure. If snapshot id is not set in the ``DEVLINK_CMD_REGION_NEW`` request kernel will allocate one and send the snapshot information to user space. +Regions may optionally allow directly reading from their contents without a +snapshot. Direct read requests are not atomic. In particular a read request +of size 256 bytes or larger will be split into multiple chunks. If atomic +access is required, use a snapshot. A driver wishing to enable this for a +region should implement the ``.read`` callback in the ``devlink_region_ops`` +structure. User space can request a direct read by using the +``DEVLINK_ATTR_REGION_DIRECT`` attribute instead of specifying a snapshot +id. + example usage ------------- @@ -65,6 +74,10 @@ example usage $ devlink region read pci/0000:00:05.0/fw-health snapshot 1 address 0 length 16 0000000000000000 0014 95dc 0014 9514 0035 1670 0034 db30 + # Read from the region without a snapshot + $ devlink region read pci/0000:00:05.0/fw-health address 16 length 16 + 0000000000000010 0000 0000 ffff ff04 0029 8c00 0028 8cc8 + As regions are likely very device or driver specific, no generic regions are defined. See the driver-specific documentation files for information on the specific regions a driver supports. |