[PATCH v1 2/2] usb: typec: tcpm: Add module parameter to wrap around logs

Badhri Jagan Sridharan
2021-05-17T23:36:18Z

When the buffer is full, TCPM stops logging into the buffer.
This change adds log_wraparound module parameter which when set
flushes out the oldest log entries (FIFO) to make way for the
newer ones.

Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
---
drivers/usb/typec/tcpm/tcpm.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index b79194919b27..a369decade60 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -38,6 +38,10 @@ static bool modparam_log_misc_dev;
module_param_named(log_misc_dev, modparam_log_misc_dev, bool, 0444);
MODULE_PARM_DESC(log_misc_dev, "Expose tcpm logs through misc device");

+static bool modparam_log_wraparound;
+module_param_named(log_wraparound, modparam_log_wraparound, bool, 0444);
+MODULE_PARM_DESC(log_wraparound, "Wrap around logs");
+
#define FOREACH_STATE(S) \
S(INVALID_STATE), \
S(TOGGLING), \
@@ -597,7 +601,7 @@ static void _tcpm_log(struct tcpm_port *port, const char *fmt, va_list args)

vsnprintf(tmpbuffer, sizeof(tmpbuffer), fmt, args);

- if (tcpm_log_full(port)) {
+ if (!modparam_log_wraparound && tcpm_log_full(port)) {
port->logbuffer_head = max(port->logbuffer_head - 1, 0);
strcpy(tmpbuffer, "overflow");
}
@@ -621,6 +625,9 @@ static void _tcpm_log(struct tcpm_port *port, const char *fmt, va_list args)
(unsigned long)ts_nsec, rem_nsec / 1000,
tmpbuffer);
port->logbuffer_head = (port->logbuffer_head + 1) % LOG_BUFFER_ENTRIES;
+ if (modparam_log_wraparound && port->logbuffer_head == port->logbuffer_tail)
+ port->logbuffer_tail =
+ (port->logbuffer_tail + 1) % LOG_BUFFER_ENTRIES;

abort:
mutex_unlock(&port->logbuffer_lock);
@@ -733,7 +740,7 @@ static int tcpm_log_show(struct seq_file *s, void *v)
seq_printf(s, "%s\n", port->logbuffer[tail]);
tail = (tail + 1) % LOG_BUFFER_ENTRIES;
}
- if (!seq_has_overflowed(s))
+ if (!modparam_log_wraparound && !seq_has_overflowed(s))
port->logbuffer_tail = tail;
mutex_unlock(&port->logbuffer_lock);

--
2.31.1.751.gd2f1c929bd-goog