ptp: add debugfs interface to see applied channel masks

Use debugfs to be able to view channel mask applied to every timestamp
event queue.

Every time the device is opened, a new entry is created in
`$DEBUGFS_MOUNTPOINT/ptpN/$INSTANCE_ADDRESS/mask`.

The mask value can be viewed grouped in 32bit decimal values using cat,
or converted to hexadecimal with the included `ptpchmaskfmt.sh` script.
32 bit values are listed from least significant to most significant.

Signed-off-by: Xabier Marquiegui <reibax@gmail.com>
Suggested-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index ac2f2b5ea0b7..282cd7d24077 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -10,6 +10,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/timekeeping.h>
+#include <linux/debugfs.h>
 
 #include <linux/nospec.h>
 
@@ -106,6 +107,7 @@ int ptp_open(struct posix_clock_context *pccontext, fmode_t fmode)
 	struct ptp_clock *ptp =
 		container_of(pccontext->clk, struct ptp_clock, clock);
 	struct timestamp_event_queue *queue;
+	char debugfsname[32];
 
 	queue = kzalloc(sizeof(*queue), GFP_KERNEL);
 	if (!queue)
@@ -119,6 +121,17 @@ int ptp_open(struct posix_clock_context *pccontext, fmode_t fmode)
 	spin_lock_init(&queue->lock);
 	list_add_tail(&queue->qlist, &ptp->tsevqs);
 	pccontext->private_clkdata = queue;
+
+	/* Debugfs contents */
+	sprintf(debugfsname, "0x%p", queue);
+	queue->debugfs_instance =
+		debugfs_create_dir(debugfsname, ptp->debugfs_root);
+	queue->dfs_bitmap.array = (u32 *)queue->mask;
+	queue->dfs_bitmap.n_elements =
+		DIV_ROUND_UP(PTP_MAX_CHANNELS, BITS_PER_BYTE * sizeof(u32));
+	debugfs_create_u32_array("mask", 0444, queue->debugfs_instance,
+				 &queue->dfs_bitmap);
+
 	return 0;
 }
 
@@ -128,6 +141,7 @@ int ptp_release(struct posix_clock_context *pccontext)
 	unsigned long flags;
 
 	if (queue) {
+		debugfs_remove(queue->debugfs_instance);
 		pccontext->private_clkdata = NULL;
 		spin_lock_irqsave(&queue->lock, flags);
 		list_del(&queue->qlist);