Date: Tue, 25 Apr 2017 13:28:42 +0300
From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org, Mats Karrman <mats.dev.list@gmail.com>,
        Badhri Jagan Sridharan <badhri@google.com>,
        Oliver Neukum <oneukum@suse.com>, Guenter Roeck <groeck@chromium.org>
Subject: Re: [RFC PATCH v5 1/2] usb: typec: USB Type-C Port Manager (tcpm)
Message-ID: <20170425102842.GD14268@kuha.fi.intel.com>
References: <1492812953-30434-1-git-send-email-linux@roeck-us.net>
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Hi Guenter,

On Fri, Apr 21, 2017 at 03:15:52PM -0700, Guenter Roeck wrote:
> +/*
> + * Logging
> + */
> +
> +#ifdef CONFIG_DEBUG_FS
> +
> +static bool tcpm_log_full(struct tcpm_port *port)
> +{
> +	return port->logbuffer_tail ==
> +		(port->logbuffer_head + 1) % LOG_BUFFER_ENTRIES;
> +}
> +
> +static void _tcpm_log(struct tcpm_port *port, const char *fmt, va_list args)
> +{
> +	char tmpbuffer[LOG_BUFFER_ENTRY_SIZE];
> +	u64 ts_nsec = local_clock();
> +	unsigned long rem_nsec;
> +
> +	if (!port->logbuffer[port->logbuffer_head]) {
> +		port->logbuffer[port->logbuffer_head] =
> +				kzalloc(LOG_BUFFER_ENTRY_SIZE, GFP_KERNEL);
> +		if (!port->logbuffer[port->logbuffer_head])
> +			return;
> +	}
> +
> +	vsnprintf(tmpbuffer, sizeof(tmpbuffer), fmt, args);
> +
> +	mutex_lock(&port->logbuffer_lock);
> +
> +	if (tcpm_log_full(port)) {
> +		port->logbuffer_head = max(port->logbuffer_head - 1, 0);
> +		strcpy(tmpbuffer, "overflow");
> +	}
> +
> +	if (port->logbuffer_head < 0 ||
> +	    port->logbuffer_head >= LOG_BUFFER_ENTRIES) {
> +		dev_warn(port->dev,
> +			 "Bad log buffer index %d\n", port->logbuffer_head);
> +		goto abort;
> +	}
> +
> +	if (!port->logbuffer[port->logbuffer_head]) {
> +		dev_warn(port->dev,
> +			 "Log buffer index %d is NULL\n", port->logbuffer_head);
> +		goto abort;
> +	}
> +
> +	rem_nsec = do_div(ts_nsec, 1000000000);
> +	scnprintf(port->logbuffer[port->logbuffer_head],
> +		  LOG_BUFFER_ENTRY_SIZE, "[%5lu.%06lu] %s",
> +		  (unsigned long)ts_nsec, rem_nsec / 1000,
> +		  tmpbuffer);
> +	port->logbuffer_head = (port->logbuffer_head + 1) % LOG_BUFFER_ENTRIES;
> +
> +abort:
> +	mutex_unlock(&port->logbuffer_lock);
> +}
> +
> +static void tcpm_log(struct tcpm_port *port, const char *fmt, ...)
> +{
> +	va_list args;
> +
> +	/* Do not log while disconnected and unattached */
> +	if (tcpm_port_is_disconnected(port) &&
> +	    (port->state == SRC_UNATTACHED || port->state == SNK_UNATTACHED ||
> +	     port->state == DRP_TOGGLING))
> +		return;
> +
> +	va_start(args, fmt);
> +	_tcpm_log(port, fmt, args);
> +	va_end(args);
> +}
> +
> +static void tcpm_log_force(struct tcpm_port *port, const char *fmt, ...)
> +{
> +	va_list args;
> +
> +	va_start(args, fmt);
> +	_tcpm_log(port, fmt, args);
> +	va_end(args);
> +}
> +
> +static int tcpm_seq_show(struct seq_file *s, void *v)
> +{
> +	struct tcpm_port *port = (struct tcpm_port *)s->private;
> +	int tail;
> +
> +	mutex_lock(&port->logbuffer_lock);
> +	tail = port->logbuffer_tail;
> +	while (tail != port->logbuffer_head) {
> +		seq_printf(s, "%s\n", port->logbuffer[tail]);
> +		tail = (tail + 1) % LOG_BUFFER_ENTRIES;
> +	}
> +	if (!seq_has_overflowed(s))
> +		port->logbuffer_tail = tail;
> +	mutex_unlock(&port->logbuffer_lock);
> +
> +	return 0;
> +}
> +
> +static int tcpm_debug_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, tcpm_seq_show, inode->i_private);
> +}
> +
> +static const struct file_operations tcpm_debug_operations = {
> +	.open		= tcpm_debug_open,
> +	.llseek		= seq_lseek,
> +	.read		= seq_read,
> +	.release	= single_release,
> +};
> +
> +static struct dentry *rootdir;
> +
> +static int tcpm_debugfs_init(struct tcpm_port *port)
> +{
> +	mutex_init(&port->logbuffer_lock);
> +	/* /sys/kernel/debug/tcpm/usbcX */
> +	if (!rootdir) {
> +		rootdir = debugfs_create_dir("tcpm", NULL);
> +		if (!rootdir)
> +			return -ENOMEM;
> +	}
> +
> +	port->dentry = debugfs_create_file(dev_name(port->dev),
> +					   S_IFREG | 0444, rootdir,
> +					   port, &tcpm_debug_operations);
> +
> +	return 0;
> +}
> +
> +static void tcpm_debugfs_exit(struct tcpm_port *port)
> +{
> +	debugfs_remove(port->dentry);
> +}
> +
> +#else
> 
> +static void tcpm_log(const struct tcpm_port *port, const char *fmt, ...) { }
> +static int tcpm_debugfs_init(const struct tcpm_port *port) { return 0; }
> +static void tcpm_debugfs_exit(const struct tcpm_port *port) { }
> +
> +#endif

I think those should be converted into tracepoints at one point.


Thanks,

-- 
heikki