netdev - [PATCH bpf-next] libbpf: clarify flags in ringbuf helpers

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Date:   Tue,  6 Apr 2021 15:58:04 -0300
From:   Pedro Tammela <pctammela@...il.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Joe Stringer <joe@...ium.io>,
        Quentin Monnet <quentin@...valent.com>,
        netdev@...r.kernel.org (open list:BPF (Safe dynamic programs and tools)),
        bpf@...r.kernel.org (open list:BPF (Safe dynamic programs and tools)),
        linux-kernel@...r.kernel.org (open list)
Cc:     Pedro Tammela <pctammela@...atatu.com>
Subject: [PATCH bpf-next] libbpf: clarify flags in ringbuf helpers

In 'bpf_ringbuf_reserve()' we require the flag to '0' at the moment.

For 'bpf_ringbuf_{discard,submit,output}' a flag of '0' might send a
notification to the process if needed.

Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
---
 include/uapi/linux/bpf.h       | 7 +++++++
 tools/include/uapi/linux/bpf.h | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 49371eba98ba..8c5c7a893b87 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4061,12 +4061,15 @@ union bpf_attr {
  * 		of new data availability is sent.
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
+ * 		If **0** is specified in *flags*, notification
+ * 		of new data availability is sent if needed.
  * 	Return
  * 		0 on success, or a negative error in case of failure.
  *
  * void *bpf_ringbuf_reserve(void *ringbuf, u64 size, u64 flags)
  * 	Description
  * 		Reserve *size* bytes of payload in a ring buffer *ringbuf*.
+ * 		*flags* must be 0.
  * 	Return
  * 		Valid pointer with *size* bytes of memory available; NULL,
  * 		otherwise.
@@ -4078,6 +4081,8 @@ union bpf_attr {
  * 		of new data availability is sent.
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
+ * 		If **0** is specified in *flags*, notification
+ * 		of new data availability is sent if needed.
  * 	Return
  * 		Nothing. Always succeeds.
  *
@@ -4088,6 +4093,8 @@ union bpf_attr {
  * 		of new data availability is sent.
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
+ * 		If **0** is specified in *flags*, notification
+ * 		of new data availability is sent if needed.
  * 	Return
  * 		Nothing. Always succeeds.
  *
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 69902603012c..51df1bd45cef 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4061,12 +4061,15 @@ union bpf_attr {
  * 		of new data availability is sent.
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
+ * 		If **0** is specified in *flags*, notification
+ * 		of new data availability is sent if needed.
  * 	Return
  * 		0 on success, or a negative error in case of failure.
  *
  * void *bpf_ringbuf_reserve(void *ringbuf, u64 size, u64 flags)
  * 	Description
  * 		Reserve *size* bytes of payload in a ring buffer *ringbuf*.
+ * 		*flags* must be 0.
  * 	Return
  * 		Valid pointer with *size* bytes of memory available; NULL,
  * 		otherwise.
@@ -4078,6 +4081,8 @@ union bpf_attr {
  * 		of new data availability is sent.
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
+ * 		If **0** is specified in *flags*, notification
+ * 		of new data availability is sent if needed.
  * 	Return
  * 		Nothing. Always succeeds.
  *
@@ -4088,6 +4093,8 @@ union bpf_attr {
  * 		of new data availability is sent.
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
+ * 		If **0** is specified in *flags*, notification
+ * 		of new data availability is sent if needed.
  * 	Return
  * 		Nothing. Always succeeds.
  *
-- 
2.25.1