RE: [net-next, v3, 02/10] ptp: support ptp physical/virtual clocks conversion

Hi Richard,

-----Original Message-----
From: Richard Cochran <richardcochran@gmail.com>
Sent: 2021年6月18日 2:28
To: Y.b. Lu <yangbo.lu@nxp.com>
Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org;
linux-kselftest@vger.kernel.org; mptcp@lists.linux.dev; David S . Miller
[off-list ref]; Jakub Kicinski [off-list ref]; Mat Martineau
[off-list ref]; Matthieu Baerts
[off-list ref]; Shuah Khan [off-list ref]; Michal
Kubecek [off-list ref]; Florian Fainelli [off-list ref];
Andrew Lunn [off-list ref]; Rui Sousa [off-list ref]; Sebastien
Laveze [off-list ref]
Subject: Re: [net-next, v3, 02/10] ptp: support ptp physical/virtual clocks
conversion

On Tue, Jun 15, 2021 at 05:45:09PM +0800, Yangbo Lu wrote:

quoted

diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h
index 3f388d63904c..6949afc9d733 100644
--- a/drivers/ptp/ptp_private.h
+++ b/drivers/ptp/ptp_private.h

@@ -46,6 +46,9 @@ struct ptp_clock {
 	const struct attribute_group *pin_attr_groups[2];
 	struct kthread_worker *kworker;
 	struct kthread_delayed_work aux_work;
+	u8 n_vclocks;

Hm, type is u8, but ...

quoted

+	struct mutex n_vclocks_mux; /* protect concurrent n_vclocks access */
+	bool vclock_flag;
 };

quoted

 #define info_to_vclock(d) container_of((d), struct ptp_vclock, info)

diff --git a/include/uapi/linux/ptp_clock.h

b/include/uapi/linux/ptp_clock.h index 1d108d597f66..4b933dc1b81b
100644

--- a/include/uapi/linux/ptp_clock.h
+++ b/include/uapi/linux/ptp_clock.h

@@ -69,6 +69,11 @@
  */
 #define PTP_PEROUT_V1_VALID_FLAGS	(0)

+/*
+ * Max number of PTP virtual clocks per PTP physical clock  */
+#define PTP_MAX_VCLOCKS			20

Only 20 clocks are allowed?  Why?

Initially I think vclock can be used for ptp multiple domains synchronization. Since the PTP domainValue is u8, u8 vclock number is large enough.
This is not a good idea to hard-code a PTP_MAX_VCLOCKS value. But it looks a little crazy to create numbers of vclocks via one command (echo n > /sys/class/ptp/ptp0/n_vclocks).
Maybe a typo creates hundreds of vclocks we don’t need. 
Do you think we should be care about setting a limitation of vclock number? Any suggestion for implementation?
Thanks.

Thanks,
Richard