Re: [PATCH v3 2/2] tty: add rpmsg driver

Jiri Slaby
2019-05-22T09:01:41Z

On 17. 05. 19, 16:27, Arnaud Pouliquen wrote:
> This driver exposes a standard tty interface on top of the rpmsg
> framework through the "rpmsg-tty-channel" rpmsg service.
>
> This driver supports multi-instances, offering a /dev/ttyRPMSGx entry
> per rpmsg endpoint.
>
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
> Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
> ---
> Documentation/serial/tty_rpmsg.txt | 38 +++
> drivers/tty/Kconfig | 9 +
> drivers/tty/Makefile | 1 +
> drivers/tty/rpmsg_tty.c | 479 +++++++++++++++++++++++++++++++++++++
> 4 files changed, 527 insertions(+)
> create mode 100644 Documentation/serial/tty_rpmsg.txt
> create mode 100644 drivers/tty/rpmsg_tty.c
>
> diff --git a/Documentation/serial/tty_rpmsg.txt b/Documentation/serial/tty_rpmsg.txt
> new file mode 100644
> index 000000000000..e069ed268a2b
> --- /dev/null
> +++ b/Documentation/serial/tty_rpmsg.txt
> @@ -0,0 +1,38 @@
> +
> + The rpmsg TTY

Perhaps you should use rst nowadays.

> diff --git a/drivers/tty/rpmsg_tty.c b/drivers/tty/rpmsg_tty.c
> new file mode 100644
> index 000000000000..c7f53352acb6
> --- /dev/null
> +++ b/drivers/tty/rpmsg_tty.c
> @@ -0,0 +1,479 @@
...
> +struct rpmsg_tty_port {
> + struct tty_port port; /* TTY port data */
> + int id; /* TTY rpmsg index */
> + struct rpmsg_device *rpdev; /* rpmsg device */
> + int cts; /* remote reception status */

Just a nit, but if you move this int to the one above, you save some
bytes thanks to alignment and holes.

> +};
> +
> +typedef void (*rpmsg_tty_rx_cb_t)(struct rpmsg_device *, void *, int, void *,
> + u32);
> +
> +static void rpmsg_tty_data_handler(struct rpmsg_device *rpdev, void *data,
> + int len, void *priv, u32 src)
> +{
> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
> + u8 *cbuf;
> + int space;
> +
> + dev_dbg(&rpdev->dev, "msg(<- src 0x%x) len %d\n", src, len);
> +
> + if (!len)
> + return;
> +
> + space = tty_prepare_flip_string(&cport->port, &cbuf, len);
> + if (space != len)
> + dev_dbg(&rpdev->dev, "trunc buffer: available space is %d\n",
> + len, space);
> + if (space <= 0)
> + return;
> +
> + memcpy(cbuf, data, space);

Why is the above not tty_insert_flip_string_fixed_flag instead?

> + tty_flip_buffer_push(&cport->port);
> +}
> +
> +static void rpmsg_tty_ctrl_handler(struct rpmsg_device *rpdev, void *data,
> + int len, void *priv, u32 src)
> +{
> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
> + struct rpmsg_tty_ctrl *ctrl = data;
> +
> + dev_dbg(&rpdev->dev, "%s: ctrl received %d\n", __func__, ctrl->ctrl);
> + print_hex_dump_debug(__func__, DUMP_PREFIX_NONE, 16, 1, data, len,
> + true);
> +
> + if (len <= sizeof(*ctrl)) {
> + dev_err(&rpdev->dev, "%s: ctrl message invalid\n", __func__);
> + return;
> + }
> +
> + if (ctrl->ctrl == DATA_TERM_READY) {

Could this be switch-case instead?

> + /* Update the CTS according to remote RTS */
> + if (!ctrl->values[0]) {
> + cport->cts = 0;
> + } else {
> + cport->cts = 1;
> + tty_port_tty_wakeup(&cport->port);
> + }
> + } else {
> + dev_err(&rpdev->dev, "unknown control ID %d\n", ctrl->ctrl);
> + }
> +}
> +
> +static const rpmsg_tty_rx_cb_t rpmsg_tty_handler[] = {
> + [RPMSG_DATA] = rpmsg_tty_data_handler,
> + [RPMSG_CTRL] = rpmsg_tty_ctrl_handler,
> +};
> +
> +static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len,
> + void *priv, u32 src)
> +{
> + struct rpmsg_tty_payload *rbuf = data;
> +
> + if (len <= sizeof(*rbuf) || rbuf->cmd > NUM_RPMSG_TTY_TYPE) {
> + dev_err(&rpdev->dev, "Invalid message: size %d, type %d\n",
> + len, rbuf->cmd);
> + return -EINVAL;
> + }
> +
> + rpmsg_tty_handler[rbuf->cmd](rpdev, &rbuf->data,
> + len - sizeof(rbuf->cmd), priv, src);

Out-of-bound access if rbuf->cmd == NUM_RPMSG_TTY_TYPE, right? Nice hole.

> +
> + return 0;
> +}
> +
> +static int rpmsg_tty_write_control(struct tty_struct *tty, u8 ctrl, u8 *values,
> + unsigned int n_value)
> +{
> + struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
> + struct rpmsg_tty_payload *msg;
> + struct rpmsg_tty_ctrl *m_ctrl;
> + struct rpmsg_device *rpdev;
> + unsigned int msg_size;
> + int ret;
> +
> + if (!cport) {
> + dev_err(tty->dev, "cannot get cport\n");
> + return -ENODEV;
> + }
> +
> + rpdev = cport->rpdev;
> +
> + msg_size = sizeof(*msg) + sizeof(*m_ctrl) + n_value;
> + msg = kzalloc(msg_size, GFP_KERNEL);
> + if (!msg)
> + return -ENOMEM;
> +
> + msg->cmd = RPMSG_CTRL;
> + m_ctrl = (struct rpmsg_tty_ctrl *)&msg->data[0];
> + m_ctrl->ctrl = DATA_TERM_READY;
> + memcpy(m_ctrl->values, values, n_value);
> +
> + ret = rpmsg_trysend(rpdev->ept, msg, msg_size);
> + if (ret < 0) {
> + dev_dbg(tty->dev, "cannot send control (%d)\n", ret);
> + ret = 0;
> + }
> + kfree(msg);
> +
> + return ret;
> +};
> +
> +static void rpmsg_tty_throttle(struct tty_struct *tty)
> +{
> + u8 rts = 0;
> +
> + /* Disable remote transmission */
> + rpmsg_tty_write_control(tty, DATA_TERM_READY, &rts, 1);
> +};
> +
> +static void rpmsg_tty_unthrottle(struct tty_struct *tty)
> +{
> + u8 rts = 1;
> +
> + /* Enable remote transmission */
> + rpmsg_tty_write_control(tty, DATA_TERM_READY, &rts, 1);
> +};
> +
> +static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty)
> +{
> + struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
> +
> + if (!cport) {
> + dev_err(tty->dev, "cannot get cport\n");
> + return -ENODEV;
> + }

Set cport to driver_data?

> +
> + return tty_port_install(&cport->port, driver, tty);
> +}
> +
> +static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp)
> +{
> + return tty_port_open(tty->port, tty, filp);
> +}
> +
> +static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp)
> +{
> + return tty_port_close(tty->port, tty, filp);
> +}
> +
> +static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len)
> +{
> + struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);

Get from driver_data?

> + struct rpmsg_device *rpdev;
> + int msg_size, msg_max_size, ret = 0;
> + int cmd_sz = sizeof(struct rpmsg_tty_payload);
> + u8 *tmpbuf;
> +
> + if (!cport) {

This would be superflous then?

> + dev_err(tty->dev, "cannot get cport\n");
> + return -ENODEV;
> + }
> +
> + /* If cts not set, the message is not sent*/
> + if (!cport->cts)
> + return 0;
> +
> + rpdev = cport->rpdev;
> +
> + dev_dbg(&rpdev->dev, "%s: send msg from tty->index = %d, len = %d\n",
> + __func__, tty->index, len);
> + if (!buf) {

How can this happen?

> + dev_err(&rpdev->dev, "buf shouldn't be null.\n");
> + return -ENOMEM;
> + }
> +
> + msg_max_size = rpmsg_get_buf_payload_size(rpdev->ept);
> + if (msg_max_size < 0)
> + return msg_max_size;
> +
> + msg_size = min(len + cmd_sz, msg_max_size);
> + tmpbuf = kzalloc(msg_size, GFP_KERNEL);
> + if (!tmpbuf)
> + return -ENOMEM;
> +
> + tmpbuf[0] = RPMSG_DATA;
> + memcpy(&tmpbuf[cmd_sz], buf, msg_size - cmd_sz);

Just curious: could "msg_size - cmd_sz" overflow to negatives? i.e.
msg_max_size < sizeof(struct rpmsg_tty_payload)?

> +
> + /*
> + * Try to send the message to remote processor, if failed return 0 as
> + * no data sent
> + */
> + ret = rpmsg_trysend(rpdev->ept, (void *)tmpbuf, msg_size);

No need to cast.

> + kfree(tmpbuf);
> + if (ret) {
> + dev_dbg(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
> + return 0;
> + }
> +
> + return msg_size - sizeof(struct rpmsg_tty_payload);

The latter is cmd_sz or not?

> +}
> +
> +static int rpmsg_tty_write_room(struct tty_struct *tty)
> +{
> + struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
> + int space = 0;
> +
> + if (!cport) {

The same as above.

> + dev_err(tty->dev, "cannot get cport\n");
> + return -ENODEV;
> + }
> +
> + /*
> + * Report the space in the rpmsg buffer, first byte is reserved to
> + * define the buffer type.
> + */
> + if (cport->cts) {
> + space = rpmsg_get_buf_payload_size(cport->rpdev->ept);
> + space -= sizeof(struct rpmsg_tty_payload);
> + }
> +
> + return space;
> +}
> +
> +static const struct tty_operations rpmsg_tty_ops = {
> + .install = rpmsg_tty_install,
> + .open = rpmsg_tty_open,
> + .close = rpmsg_tty_close,
> + .write = rpmsg_tty_write,
> + .write_room = rpmsg_tty_write_room,
> + .throttle = rpmsg_tty_throttle,
> + .unthrottle = rpmsg_tty_unthrottle,
> +};
> +
> +static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void)
> +{
> + struct rpmsg_tty_port *cport;
> +
> + cport = kzalloc(sizeof(*cport), GFP_KERNEL);
> + if (!cport)
> + return ERR_PTR(-ENOMEM);
> +
> + mutex_lock(&idr_lock);
> + cport->id = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL);
> + mutex_unlock(&idr_lock);
> +
> + if (cport->id < 0) {
> + kfree(cport);
> + return ERR_PTR(-ENOSPC);
> + }
> +
> + return cport;
> +}
> +
> +static void rpmsg_tty_release_cport(struct rpmsg_tty_port *cport)
> +{
> + mutex_lock(&idr_lock);
> + idr_remove(&tty_idr, cport->id);
> + mutex_unlock(&idr_lock);
> +
> + kfree(cport);
> +}
> +
> +static int rpmsg_tty_port_activate(struct tty_port *p, struct tty_struct *tty)
> +{
> + /* Allocate the buffer we use for writing data */
> + return tty_port_alloc_xmit_buf(p);
> +}
> +
> +static void rpmsg_tty_port_shutdown(struct tty_port *p)
> +{
> + /* Free the write buffer */
> + tty_port_free_xmit_buf(p);
> +}
> +
> +static void rpmsg_tty_dtr_rts(struct tty_port *port, int raise)
> +{
> + struct rpmsg_tty_port *cport =
> + container_of(port, struct rpmsg_tty_port, port);
> +
> + pr_debug("%s: dtr_rts state %d\n", __func__, raise);
> + if (!port->tty || !cport) {

The latter barely can happen given you use container_of above.

> + pr_err("invalid port\n");
> + return;
> + }
> +
> + cport->cts = raise;
> +
> + if (raise)
> + rpmsg_tty_unthrottle(port->tty);
> + else
> + rpmsg_tty_throttle(port->tty);
> +}
> +
> +static const struct tty_port_operations rpmsg_tty_port_ops = {
> + .activate = rpmsg_tty_port_activate,
> + .shutdown = rpmsg_tty_port_shutdown,
> + .dtr_rts = rpmsg_tty_dtr_rts,
> +};
> +
> +static int rpmsg_tty_probe(struct rpmsg_device *rpdev)
> +{
> + struct rpmsg_tty_port *cport;
> + struct device *dev = &rpdev->dev;
> + struct device *tty_dev;
> + int ret;
> +
> + cport = rpmsg_tty_alloc_cport();
> + if (IS_ERR(cport)) {
> + dev_err(dev, "failed to alloc tty port\n");
> + return PTR_ERR(cport);
> + }
> +
> + tty_port_init(&cport->port);
> + cport->port.low_latency = cport->port.flags | ASYNC_LOW_LATENCY;

"|"? Not "&"? You should prepend "!!" in any way as low latency is 13th bit.

> + cport->port.ops = &rpmsg_tty_port_ops;
> +
> + tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver,
> + cport->id, dev);
> + if (IS_ERR(tty_dev)) {
> + dev_err(dev, "failed to register tty port\n");
> + ret = PTR_ERR(tty_dev);
> + goto err_destroy;
> + }
...
regards,
--
js
suse labs