Commit a81cf979 authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
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cdc-acm: implement put_char() and flush_chars() 



This should cut down latencies and waste if the tty layer writes single bytes.

Signed-off-by: default avatarOliver Neukum <&gt;oneukum@suse.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ca1c3e6f

drivers/usb/class/cdc-acm.c

+67 −0
Original line number Diff line number Diff line
@@ -713,9 +713,20 @@ static int acm_tty_write(struct tty_struct *tty, 
	}



	if (acm->susp_count) {

		if (acm->putbuffer) {

			/* now to preserve order */

			usb_anchor_urb(acm->putbuffer->urb, &acm->delayed);

			acm->putbuffer = NULL;

		}

		usb_anchor_urb(wb->urb, &acm->delayed);

		spin_unlock_irqrestore(&acm->write_lock, flags);

		return count;

	} else {

		if (acm->putbuffer) {

			/* at this point there is no good way to handle errors */

			acm_start_wb(acm, acm->putbuffer);

			acm->putbuffer = NULL;

		}

	}



	stat = acm_start_wb(acm, wb);
@@ -726,6 +737,60 @@ static int acm_tty_write(struct tty_struct *tty, 
	return count;

}



static void acm_tty_flush_chars(struct tty_struct *tty)

{

	struct acm *acm = tty->driver_data;

	struct acm_wb *cur = acm->putbuffer;

	int err;

	unsigned long flags;



	acm->putbuffer = NULL;

	err = usb_autopm_get_interface_async(acm->control);

	spin_lock_irqsave(&acm->write_lock, flags);

	if (err < 0) {

		cur->use = 0;

		goto out;

	}



	if (acm->susp_count)

		usb_anchor_urb(cur->urb, &acm->delayed);

	else

		acm_start_wb(acm, cur);

out:

	spin_unlock_irqrestore(&acm->write_lock, flags);

	return;

}



static int acm_tty_put_char(struct tty_struct *tty, unsigned char ch)

{

	struct acm *acm = tty->driver_data;

	struct acm_wb *cur;

	int wbn;

	unsigned long flags;



overflow:

	cur = acm->putbuffer;

	if (!cur) {

		spin_lock_irqsave(&acm->write_lock, flags);

		wbn = acm_wb_alloc(acm);

		if (wbn >= 0) {

			cur = &acm->wb[wbn];

			acm->putbuffer = cur;

		}

		spin_unlock_irqrestore(&acm->write_lock, flags);

		if (!cur)

			return 0;

	}



	if (cur->len == acm->writesize) {

		acm_tty_flush_chars(tty);

		goto overflow;

	}



	cur->buf[cur->len++] = ch;

	return 1;

}



static int acm_tty_write_room(struct tty_struct *tty)

{

	struct acm *acm = tty->driver_data;
@@ -1905,6 +1970,8 @@ static const struct tty_operations acm_ops = { 
	.cleanup =		acm_tty_cleanup,

	.hangup =		acm_tty_hangup,

	.write =		acm_tty_write,

	.put_char =		acm_tty_put_char,

	.flush_chars =		acm_tty_flush_chars,

	.write_room =		acm_tty_write_room,

	.ioctl =		acm_tty_ioctl,

	.throttle =		acm_tty_throttle,

drivers/usb/class/cdc-acm.h

+1 −0
Original line number Diff line number Diff line
@@ -94,6 +94,7 @@ struct acm { 
	unsigned long read_urbs_free;

	struct urb *read_urbs[ACM_NR];

	struct acm_rb read_buffers[ACM_NR];

	struct acm_wb *putbuffer;			/* for acm_tty_put_char() */

	int rx_buflimit;

	int rx_endpoint;

	spinlock_t read_lock;