Received-SPF: pass (google.com: domain of linux-kernel+bounces-1730-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Received-SPF: Pass (protection.outlook.com: domain of opensynergy.com
 designates 217.66.60.4 as permitted sender) receiver=protection.outlook.com;
 client-ip=217.66.60.4; helo=SR-MAIL-03.open-synergy.com; pr=C
From: Peter Hilber <peter.hilber@opensynergy.com>
To: linux-kernel@vger.kernel.org
Cc: Peter Hilber <peter.hilber@opensynergy.com>,
	"D, Lakshmi Sowjanya" <lakshmi.sowjanya.d@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	jstultz@google.com,
	giometti@enneenne.com,
	corbet@lwn.net,
	andriy.shevchenko@linux.intel.com,
	"Dong, Eddie" <eddie.dong@intel.com>,
	"Hall, Christopher S" <christopher.s.hall@intel.com>,
	Marc Zyngier <maz@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org,
	"H. Peter Anvin" <hpa@zytor.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Richard Cochran <richardcochran@gmail.com>,
	kvm@vger.kernel.org,
	netdev@vger.kernel.org,
	Stephen Boyd <sboyd@kernel.org>
Subject: [RFC PATCH v2 1/7] timekeeping: Add clocksource ID to struct system_counterval_t
Date: Fri, 15 Dec 2023 23:06:06 +0100
Message-Id: <20231215220612.173603-2-peter.hilber@opensynergy.com>
In-Reply-To: <20231215220612.173603-1-peter.hilber@opensynergy.com>
References: <20231215220612.173603-1-peter.hilber@opensynergy.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Dec 2023 22:06:31.9216
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 63315aeb-092b-4706-5d21-08dbfdba1882
X-MS-Exchange-CrossTenant-Id: 800fae25-9b1b-4edc-993d-c939c4e84a64
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=800fae25-9b1b-4edc-993d-c939c4e84a64;Ip=[217.66.60.4];Helo=[SR-MAIL-03.open-synergy.com]
X-MS-Exchange-CrossTenant-AuthSource:
	AM6EUR05FT007.eop-eur05.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BEZP281MB2021
X-TM-AS-ERS: 104.47.11.169-0.0.0.0
X-TMASE-Version: StarCloud-1.3-9.1.1015-28060.002
X-TMASE-Result: 10--1.225700-4.000000
X-TMASE-MatchedRID: I6rpFm0lrcMEZ1mm50iAbgs6eGQ6Ral9EkUS8Erng9pzi8z2Fvgo+kp9
	UxJnBl3FHDf9l7U5F7SnyNbHJWoNRbkeKW6KfnZEiu6u4shZ+fHcHWFKCmADc2shUDcgZ8ILoMQ
	NBr66IpTrLAe8bL+cp6EWqZPwachiifyRQLERY0pCPQBD3xA/3aODSWu0oxbK6gfKtA7Yhlrtmy
	EvxwC5ZF4L45p2p0pV3+6k97GsyDgqZdHEYvGr9R+AJsLlsQNEJEWB6QUw47pwgry9e+z6K02xv
	NT0DEAe
X-TMASE-XGENCLOUD: e75e3261-40d8-4d1c-aac9-f728c685c5cd-0-0-200-0
X-TM-Deliver-Signature: 4B42FBC32BA0165278B8D7FEBEE10FBB
X-TM-Addin-Auth: lofU8dU7CdFAhD8V9sagn575AEfwI3X3ytRWn+nIQZBRhSeZKXpgWtk8ubW
	QsBx7yYGxPJkY5F/LuMy6srgWd65Qo9+qbrJx0kkJwJbZ7I308Dkk+O54/YXj5rQOiQ8GX33POb
	tI+wMsWLHcGhZAb2HqQZ2d8iE9WKWeV0fo06u2vUq5+u9LpVu9Q0EXqKR7IBL9Pbpzy6TVoJHxO
	ZVKdGzMhvoYlpRbbpEAAF7n6HO5Zz/ESbRSFRAKocnepMuUrzQkaY9FFpK1+mNYwquPne2LevC8
	XXE8/nOWtZqmvQM=.bPpDQlzcOcNoYt9A5H77a9CR386jDRBzQLsgklYU2XMC+ekPsNsfD1BP4A
	Jcb6vPqH/K8HQnLDHrWQFe4mpSdqnShAFqd3aOLNfdPEO08subNevpkOxsjEM6cgsECDXl3VXul
	ORxePK6hlb+HjiJdpifFwSMaiK8h6Up9Y2F3cMoK3utczzCmVZAJBN34jqyVWgruSlZ5Sasdk+t
	vZIJdF/oMam1o+kAAkKUrZS4lHhAy3jlxW0GqQ/B1RPFKHO+3x2EIAk2DQRfLe6551X6wH9YczS
	n2itYa2/OSiyu5Ng1EKUPUVwBELXWXr/49ibhsRpDc7fUnoMUDHJ+ClcjLQ==
X-TM-Addin-ProductCode: EMS
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=opensynergy.com;
	s=TM-DKIM-20210503141657; t=1702677995;
	bh=O8MqEDHj5ZPOM57SiFoYrD63DRexH/0RpOMiWwTA4kQ=; l=1727;
	h=From:To:Date;
	b=UrFihNp8K98r1vYbUF27TVe5ZLFY893mdg+6qxxVieR3os+tsgkRTv3vd47WKCotM
	 VO7if4ZlAgEs4+ifyEtmIYcB22F8y8jQdJT8vYcvF5zybfsQIpxQT+xrEiVIcb3xng
	 kAL2FqO7bJlKS0P0gl1TbsxFQM1ZgWMR8/G9Hb/GonrRcu83orW6RAGcshIR0JQ/5o
	 jg7tkio3dvaVTLF8pdrnvBRkh6RX4TJDP5eXRwKfqhqKbraoJRrN3wssNqJkbDYqmn
	 OquQ5QckNTMao5/XvlIDEadWKIwwWJl9nrOp8OJaJGYGjFydGdZXrB294q6wuoBfBw
	 ocH7CA6JWChBg==

Clocksource pointers can be problematic to obtain for drivers which are not
clocksource drivers themselves. In particular, the RFC virtio_rtc driver
[1] would require a new helper function to obtain a pointer to the Arm
Generic Timer clocksource. The ptp_kvm driver also required a similar
workaround.

Add a clocksource ID member to struct system_counterval_t, which in the
future shall identify the clocksource, and shall replace the struct
clocksource * member. By this, get_device_system_crosststamp() callers
(such as virtio_rtc and ptp_kvm) will be able to supply easily accessible
clocksource ids instead of clocksource pointers.

[1] https://lore.kernel.org/lkml/20230818012014.212155-1-peter.hilber@opensynergy.com/

Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
---

Notes:
    v2:
    
    - Refer to clocksource IDs as such in comments (Thomas Gleixner).

 include/linux/timekeeping.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index fe1e467ba046..74dc7c8b036f 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -272,10 +272,15 @@ struct system_device_crosststamp {
  * @cycles:	System counter value
  * @cs:		Clocksource corresponding to system counter value. Used by
  *		timekeeping code to verify comparibility of two cycle values
+ * @cs_id:	Clocksource ID corresponding to system counter value. To be
+ *		used instead of cs in the future.
+ *		The default ID, CSID_GENERIC, does not identify a specific
+ *		clocksource.
  */
 struct system_counterval_t {
 	u64			cycles;
 	struct clocksource	*cs;
+	enum clocksource_ids	cs_id;
 };
 
 /*
-- 
2.40.1