linux-kernel - Re: [PATCH v5] PCI: hotplug: Add a generic RAS tracepoint for hotplug event

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Message-ID: <20250113155503.71467082@gandalf.local.home>
Date: Mon, 13 Jan 2025 15:55:03 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Shuai Xue <xueshuai@...ux.alibaba.com>
Cc: lukas@...ner.de, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, helgaas@...nel.org,
 bhelgaas@...gle.com, tony.luck@...el.com, bp@...en8.de,
 mhiramat@...nel.org, mathieu.desnoyers@...icios.com, oleg@...hat.com,
 naveen@...nel.org, davem@...emloft.net, anil.s.keshavamurthy@...el.com,
 mark.rutland@....com, peterz@...radead.org, tianruidong@...ux.alibaba.com
Subject: Re: [PATCH v5] PCI: hotplug: Add a generic RAS tracepoint for
 hotplug event

On Thu,  9 Jan 2025 10:55:43 +0800
Shuai Xue <xueshuai@...ux.alibaba.com> wrote:

> diff --git a/drivers/pci/hotplug/trace.h b/drivers/pci/hotplug/trace.h
> new file mode 100644
> index 000000000000..5b60cd7bcffb
> --- /dev/null
> +++ b/drivers/pci/hotplug/trace.h
> @@ -0,0 +1,68 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#if !defined(_TRACE_HW_EVENT_PCI_HP_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_HW_EVENT_PCI_HP_H
> +
> +#include <linux/tracepoint.h>
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM pci
> +
> +#define PCI_HOTPLUG_EVENT					\
> +	EM(PCI_HOTPLUG_LINK_UP,			"Link Up")	\
> +	EM(PCI_HOTPLUG_LINK_DOWN,		"Link Down")	\
> +	EM(PCI_HOTPLUG_CARD_PRESENT,		"Card present")	\
> +	EMe(PCI_HOTPLUG_CARD_NOT_PRESENT,	"Card not present")

Since you are creating these enums in this patch, you can also do a
shortcut here too. Instead of doing the define here, move it to
include/uapi/linux/pci.h:

> +
> +/* Enums require being exported to userspace, for user tool parsing */
> +#undef EM
> +#undef EMe
> +#define EM(a, b)	TRACE_DEFINE_ENUM(a);
> +#define EMe(a, b)	TRACE_DEFINE_ENUM(a);
> +
> +PCI_HOTPLUG_EVENT
> +
> +/*
> + * Now redefine the EM() and EMe() macros to map the enums to the strings
> + * that will be printed in the output.
> + */
> +#undef EM
> +#undef EMe
> +#define EM(a, b)	{a, b},
> +#define EMe(a, b)	{a, b}
> +
> +TRACE_EVENT(pci_hp_event,
> +
> +	TP_PROTO(const char *port_name,
> +		 const char *slot,
> +		 const int event),
> +
> +	TP_ARGS(port_name, slot, event),
> +
> +	TP_STRUCT__entry(
> +		__string(	port_name,	port_name	)
> +		__string(	slot,		slot		)
> +		__field(	int,		event	)
> +	),
> +
> +	TP_fast_assign(
> +		__assign_str(port_name);
> +		__assign_str(slot);
> +		__entry->event = event;
> +	),
> +
> +	TP_printk("%s slot:%s, event:%s\n",
> +		__get_str(port_name),
> +		__get_str(slot),
> +		__print_symbolic(__entry->event, PCI_HOTPLUG_EVENT)
> +	)
> +);
> +
> +#endif /* _TRACE_HW_EVENT_PCI_HP_H */
> +
> +#undef TRACE_INCLUDE_PATH
> +#define TRACE_INCLUDE_PATH  ../../drivers/pci/hotplug
> +#undef TRACE_INCLUDE_FILE
> +#define TRACE_INCLUDE_FILE trace
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> diff --git a/include/uapi/linux/pci.h b/include/uapi/linux/pci.h
> index a769eefc5139..4f150028965d 100644
> --- a/include/uapi/linux/pci.h
> +++ b/include/uapi/linux/pci.h
> @@ -39,4 +39,11 @@
>  #define PCIIOC_MMAP_IS_MEM	(PCIIOC_BASE | 0x02)	/* Set mmap state to MEM space. */
>  #define PCIIOC_WRITE_COMBINE	(PCIIOC_BASE | 0x03)	/* Enable/disable write-combining. */
>  
> +enum pci_hotplug_event {
> +	PCI_HOTPLUG_LINK_UP,
> +	PCI_HOTPLUG_LINK_DOWN,
> +	PCI_HOTPLUG_CARD_PRESENT,
> +	PCI_HOTPLUG_CARD_NOT_PRESENT,
> +};

Instead of defining the enum as you did above, if you have the define of
the enums here, you could do:

#define PCI_HOTPLUG_EVENT					\
	EM(PCI_HOTPLUG_LINK_UP,			"Link Up")	\
	EM(PCI_HOTPLUG_LINK_DOWN,		"Link Down")	\
	EM(PCI_HOTPLUG_CARD_PRESENT,		"Card present")	\
	EMe(PCI_HOTPLUG_CARD_NOT_PRESENT,	"Card not present")

#undef EM
#undef EMe
#define EM(a, b)	a,
#define EMe(a, b)	a,

enum pci_hotplug_event {
	PCI_HOTPLUG_EVENT
};

Then you only have one place to worry about adding new enums ;-)

-- Steve

> +
>  #endif /* _UAPILINUX_PCI_H */