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-rw-r--r--Documentation/powerpc/cxlflash.txt42
1 files changed, 38 insertions, 4 deletions
diff --git a/Documentation/powerpc/cxlflash.txt b/Documentation/powerpc/cxlflash.txt
index 4202d1bc583c..f4c119092b98 100644
--- a/Documentation/powerpc/cxlflash.txt
+++ b/Documentation/powerpc/cxlflash.txt
@@ -171,11 +171,30 @@ DK_CXLFLASH_ATTACH
destroyed, the tokens are to be considered stale and subsequent
usage will result in errors.
+ - A valid adapter file descriptor (fd2 >= 0) is only returned on
+ the initial attach for a context. Subsequent attaches to an
+ existing context (DK_CXLFLASH_ATTACH_REUSE_CONTEXT flag present)
+ do not provide the adapter file descriptor as it was previously
+ made known to the application.
+
- When a context is no longer needed, the user shall detach from
- the context via the DK_CXLFLASH_DETACH ioctl.
+ the context via the DK_CXLFLASH_DETACH ioctl. When this ioctl
+ returns with a valid adapter file descriptor and the return flag
+ DK_CXLFLASH_APP_CLOSE_ADAP_FD is present, the application _must_
+ close the adapter file descriptor following a successful detach.
+
+ - When this ioctl returns with a valid fd2 and the return flag
+ DK_CXLFLASH_APP_CLOSE_ADAP_FD is present, the application _must_
+ close fd2 in the following circumstances:
+
+ + Following a successful detach of the last user of the context
+ + Following a successful recovery on the context's original fd2
+ + In the child process of a fork(), following a clone ioctl,
+ on the fd2 associated with the source context
- - A close on fd2 will invalidate the tokens. This operation is not
- required by the user.
+ - At any time, a close on fd2 will invalidate the tokens. Applications
+ should exercise caution to only close fd2 when appropriate (outlined
+ in the previous bullet) to avoid premature loss of I/O.
DK_CXLFLASH_USER_DIRECT
-----------------------
@@ -254,6 +273,10 @@ DK_CXLFLASH_DETACH
success, all "tokens" which had been provided to the user from the
DK_CXLFLASH_ATTACH onward are no longer valid.
+ When the DK_CXLFLASH_APP_CLOSE_ADAP_FD flag was returned on a successful
+ attach, the application _must_ close the fd2 associated with the context
+ following the detach of the final user of the context.
+
DK_CXLFLASH_VLUN_CLONE
----------------------
This ioctl is responsible for cloning a previously created
@@ -261,7 +284,7 @@ DK_CXLFLASH_VLUN_CLONE
support maintaining user space access to storage after a process
forks. Upon success, the child process (which invoked the ioctl)
will have access to the same LUNs via the same resource handle(s)
- and fd2 as the parent, but under a different context.
+ as the parent, but under a different context.
Context sharing across processes is not supported with CXL and
therefore each fork must be met with establishing a new context
@@ -275,6 +298,12 @@ DK_CXLFLASH_VLUN_CLONE
translation tables are copied from the parent context to the child's
and then synced with the AFU.
+ When the DK_CXLFLASH_APP_CLOSE_ADAP_FD flag was returned on a successful
+ attach, the application _must_ close the fd2 associated with the source
+ context (still resident/accessible in the parent process) following the
+ clone. This is to avoid a stale entry in the file descriptor table of the
+ child process.
+
DK_CXLFLASH_VERIFY
------------------
This ioctl is used to detect various changes such as the capacity of
@@ -309,6 +338,11 @@ DK_CXLFLASH_RECOVER_AFU
at which time the context/resources they held will be freed as part of
the release fop.
+ When the DK_CXLFLASH_APP_CLOSE_ADAP_FD flag was returned on a successful
+ attach, the application _must_ unmap and close the fd2 associated with the
+ original context following this ioctl returning success and indicating that
+ the context was recovered (DK_CXLFLASH_RECOVER_AFU_CONTEXT_RESET).
+
DK_CXLFLASH_MANAGE_LUN
----------------------
This ioctl is used to switch a LUN from a mode where it is available