On Thu, Dec 10, 2020 at 05:05:17PM +0100, Greg Kroah-Hartman wrote:
> From: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
>
> TCPM logs overflow once the logbuffer is full. Clear old entries and
> allow logging the newer ones as the newer would be more relevant to the
> issue being debugged.
>
> Also, do not reset the logbuffer tail as end users might take back to
> back bugreports which would result in an empty buffer.
>
Historically, the reason for not doing this was that, once a problem occurs,
the log would fill up quickly (typically with reconnect attempts), and the
actual reason for the problem would be overwritten. Maybe that reasoning
no longer applies; I just wanted to point out that there _was_ a reason for
not clearing old log entries.
Guenter
> Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
> Cc: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> Cc: Kyle Tso <kyletso@xxxxxxxxxx>
> Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
> Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/usb/typec/tcpm/tcpm.c | 16 +++-------------
> 1 file changed, 3 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index cedc6cf82d61..0ceeab50ed64 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -470,12 +470,6 @@ static bool tcpm_port_is_disconnected(struct tcpm_port *port)
>
> #ifdef CONFIG_DEBUG_FS
>
> -static bool tcpm_log_full(struct tcpm_port *port)
> -{
> - return port->logbuffer_tail ==
> - (port->logbuffer_head + 1) % LOG_BUFFER_ENTRIES;
> -}
> -
> __printf(2, 0)
> static void _tcpm_log(struct tcpm_port *port, const char *fmt, va_list args)
> {
> @@ -495,11 +489,6 @@ 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)) {
> - 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,
> @@ -519,6 +508,9 @@ 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 (port->logbuffer_head == port->logbuffer_tail)
> + port->logbuffer_tail =
> + (port->logbuffer_tail + 1) % LOG_BUFFER_ENTRIES;
>
> abort:
> mutex_unlock(&port->logbuffer_lock);
> @@ -622,8 +614,6 @@ static int tcpm_debug_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))
> - port->logbuffer_tail = tail;
> mutex_unlock(&port->logbuffer_lock);
>
> return 0;
> --
> 2.29.2
>
