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s390_sthyi.2: Some minor additions 

* man2/s390_sthyi.2
  (.SH DESCRIPTION): Document the size of the resp_buffer when
    function_code is 0.
  (.SH NOTES): Document various aspects of the current
    implementation (the lifted requirement for the response buffer
    alignment, the presence of in-kernel cache), add description
    for the documentation URL.

Coauthored-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Eugene Syromyatnikov 2018-04-14 18:43:46 +02:00 committed by Michael Kerrisk
parent 03b3fa4a74
commit b2c7f822c6
1 changed files with 11 additions and 0 deletions
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man2/s390_sthyi.2
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@ -53,6 +53,9 @@ capacity information.
The
.I resp_buffer
argument specifies the address of a response buffer.
When the
.I function_code
is 0, it has to be one page (4K) in size.
If the system call returns 0,
the response buffer will be filled with CPU capacity information.
Otherwise, the response buffer's content is unchanged.
@ -126,6 +129,14 @@ to call it.
.PP
For details of the STHYI instruction, see
.UR https://www.ibm.com\:/support\:/knowledgecenter\:/SSB27U_6.3.0\:/com.ibm.zvm.v630.hcpb4\:/hcpb4sth.htm
the documentation page
.UE .
.PP
When the system call interface is used, the response buffer doesn't
have to fulfill alignment requirements described in the STHYI
instruction definition.
.PP
The kernel caches the response (for up to one second, as of Linux 4.16).
Subsequent system call invocations may return the cached response.
.SH SEE ALSO
.BR syscall (2)