ptp: support event queue reader channel masks

On systems with multiple timestamp event channels, some readers might
want to receive only a subset of those channels.

Add the necessary modifications to support timestamp event channel
filtering, including two IOCTL operations:

- Clear all channels
- Enable one channel

The mask modification operations will be applied exclusively on the
event queue assigned to the file descriptor used on the IOCTL operation,
so the typical procedure to have a reader receiving only a subset of the
enabled channels would be:

- Open device file
- ioctl: clear all channels
- ioctl: enable one channel
- start reading

Calling the enable one channel ioctl more than once will result in
multiple enabled channels.

Signed-off-by: Xabier Marquiegui <[e-mail]>
Suggested-by: Richard Cochran <[e-mail]>
Suggested-by: Vinicius Costa Gomes <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/ptp/ptp_chardev.c

···
 	queue = kzalloc(sizeof(*queue), GFP_KERNEL);
 	if (!queue)
 		return -EINVAL;
+	queue->mask = bitmap_alloc(PTP_MAX_CHANNELS, GFP_KERNEL);
+	if (!queue->mask) {
+		kfree(queue);
+		return -EINVAL;
+	}
+	bitmap_set(queue->mask, 0, PTP_MAX_CHANNELS);
 	spin_lock_init(&queue->lock);
 	list_add_tail(&queue->qlist, &ptp->tsevqs);
 	pccontext->private_clkdata = queue;
···
 		spin_lock_irqsave(&queue->lock, flags);
 		list_del(&queue->qlist);
 		spin_unlock_irqrestore(&queue->lock, flags);
+		bitmap_free(queue->mask);
 		kfree(queue);
 	}
 	return 0;
···
 	struct system_device_crosststamp xtstamp;
 	struct ptp_clock_info *ops = ptp->info;
 	struct ptp_sys_offset *sysoff = NULL;
+	struct timestamp_event_queue *tsevq;
 	struct ptp_system_timestamp sts;
 	struct ptp_clock_request req;
 	struct ptp_clock_caps caps;
···
 	struct ptp_pin_desc pd;
 	struct timespec64 ts;
 	int enable, err = 0;
+
+	tsevq = pccontext->private_clkdata;
 
 	switch (cmd) {
 
···
 			return -ERESTARTSYS;
 		err = ptp_set_pinfunc(ptp, pin_index, pd.func, pd.chan);
 		mutex_unlock(&ptp->pincfg_mux);
+		break;
+
+	case PTP_MASK_CLEAR_ALL:
+		bitmap_clear(tsevq->mask, 0, PTP_MAX_CHANNELS);
+		break;
+
+	case PTP_MASK_EN_SINGLE:
+		if (copy_from_user(&i, (void __user *)arg, sizeof(i))) {
+			err = -EFAULT;
+			break;
+		}
+		if (i >= PTP_MAX_CHANNELS) {
+			err = -EFAULT;
+			break;
+		}
+		set_bit(i, tsevq->mask);
 		break;
 
 	default:

drivers/ptp/ptp_clock.c

···
 	spin_lock_irqsave(&tsevq->lock, flags);
 	list_del(&tsevq->qlist);
 	spin_unlock_irqrestore(&tsevq->lock, flags);
+	bitmap_free(tsevq->mask);
 	kfree(tsevq);
 	ida_free(&ptp_clocks_map, ptp->index);
 	kfree(ptp);
···
 	if (!queue)
 		goto no_memory_queue;
 	list_add_tail(&queue->qlist, &ptp->tsevqs);
+	queue->mask = bitmap_alloc(PTP_MAX_CHANNELS, GFP_KERNEL);
+	if (!queue->mask)
+		goto no_memory_bitmap;
+	bitmap_set(queue->mask, 0, PTP_MAX_CHANNELS);
 	spin_lock_init(&queue->lock);
 	mutex_init(&ptp->pincfg_mux);
 	mutex_init(&ptp->n_vclocks_mux);
···
 kworker_err:
 	mutex_destroy(&ptp->pincfg_mux);
 	mutex_destroy(&ptp->n_vclocks_mux);
+	bitmap_free(queue->mask);
+no_memory_bitmap:
 	list_del(&queue->qlist);
 	kfree(queue);
 no_memory_queue:
···
 		break;
 
 	case PTP_CLOCK_EXTTS:
-		/* Enqueue timestamp on all queues */
+		/* Enqueue timestamp on selected queues */
 		list_for_each_entry(tsevq, &ptp->tsevqs, qlist) {
-			enqueue_external_timestamp(tsevq, event);
+			if (test_bit((unsigned int)event->index, tsevq->mask))
+				enqueue_external_timestamp(tsevq, event);
 		}
 		wake_up_interruptible(&ptp->tsev_wq);
 		break;

drivers/ptp/ptp_private.h

···
 #include <linux/ptp_clock_kernel.h>
 #include <linux/time.h>
 #include <linux/list.h>
+#include <linux/bitmap.h>
 
 #define PTP_MAX_TIMESTAMPS 128
 #define PTP_BUF_TIMESTAMPS 30
 #define PTP_DEFAULT_MAX_VCLOCKS 20
+#define PTP_MAX_CHANNELS 2048
 
 struct timestamp_event_queue {
 	struct ptp_extts_event buf[PTP_MAX_TIMESTAMPS];
···
 	int tail;
 	spinlock_t lock;
 	struct list_head qlist;
+	unsigned long *mask;
 };
 
 struct ptp_clock {

include/uapi/linux/ptp_clock.h

···
 	_IOWR(PTP_CLK_MAGIC, 17, struct ptp_sys_offset_precise)
 #define PTP_SYS_OFFSET_EXTENDED2 \
 	_IOWR(PTP_CLK_MAGIC, 18, struct ptp_sys_offset_extended)
+#define PTP_MASK_CLEAR_ALL  _IO(PTP_CLK_MAGIC, 19)
+#define PTP_MASK_EN_SINGLE  _IOW(PTP_CLK_MAGIC, 20, unsigned int)
 
 struct ptp_extts_event {
 	struct ptp_clock_time t; /* Time event occured. */