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SubjectRe: [PATCH v7 2/2] tty: add rpmsg driver
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On 24. 03. 20, 18:04, Arnaud Pouliquen wrote:
> --- /dev/null
> +++ b/drivers/tty/rpmsg_tty.c
> @@ -0,0 +1,417 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) STMicroelectronics 2020 - All Rights Reserved
> + * Authors: Arnaud Pouliquen <arnaud.pouliquen@st.com> for STMicroelectronics.
> + */
...
> +typedef void (*rpmsg_tty_rx_cb_t)(struct rpmsg_device *, void *, int, void *,
> + u32);

Unused, it seems?

> +static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len,
> + void *priv, u32 src)
> +{
> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev);
> + int copied;
> +
> + if (src == cport->data_dst) {
> + /* data message */
> + if (!len)
> + return -EINVAL;
> + copied = tty_insert_flip_string_fixed_flag(&cport->port, data,
> + TTY_NORMAL, len);

Provided you always pass TTY_NORMAL, why not simply call
tty_insert_flip_string instead?

> + if (copied != len)
> + dev_dbg(&rpdev->dev, "trunc buffer: available space is %d\n",
> + copied);
> + tty_flip_buffer_push(&cport->port);
> + } else {
> + /* control message */
> + struct rpmsg_tty_ctrl *msg = data;
> +
> + if (len != sizeof(*msg))
> + return -EINVAL;
> +
> + cport->data_dst = msg->d_ept_addr;
> +
> + /* Update remote cts state */
> + cport->cts = msg->cts ? 1 : 0;

Number to bool implicit conversion needs no magic, just do:
cport->cts = msg->cts;

> + if (cport->cts)
> + tty_port_tty_wakeup(&cport->port);
> + }
> +
> + return 0;
> +}
> +
> +static void rpmsg_tty_send_term_ready(struct tty_struct *tty, u8 state)

Should the state be bool? Should it be named "ready" instead?

> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> + struct rpmsg_tty_ctrl m_ctrl;
> + int ret;
> +
> + m_ctrl.cts = state;
> + m_ctrl.d_ept_addr = cport->d_ept->addr;
> +
> + ret = rpmsg_trysend(cport->cs_ept, &m_ctrl, sizeof(m_ctrl));
> + if (ret < 0)
> + dev_dbg(tty->dev, "cannot send control (%d)\n", ret);
> +};
> +
> +static void rpmsg_tty_throttle(struct tty_struct *tty)
> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> +
> + /* Disable remote transmission */
> + if (cport->cs_ept)
> + rpmsg_tty_send_term_ready(tty, 0);

then s/0/false/;

> +};
> +
> +static void rpmsg_tty_unthrottle(struct tty_struct *tty)
> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> +
> + /* Enable remote transmission */
> + if (cport->cs_ept)
> + rpmsg_tty_send_term_ready(tty, 1);

and s/1/true/;

> +};
...
> +static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len)
> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> + struct rpmsg_device *rpdev;
> + int msg_max_size, msg_size;
> + int ret;
> + u8 *tmpbuf;
> +
> + /* 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);
> +
> + msg_max_size = rpmsg_get_mtu(rpdev->ept);
> +
> + msg_size = min(len, msg_max_size);
> + tmpbuf = kzalloc(msg_size, GFP_KERNEL);
> + if (!tmpbuf)
> + return -ENOMEM;
> +
> + memcpy(tmpbuf, buf, msg_size);

This is kmemdup, but why do you do that in the first place?

> + /*
> + * Try to send the message to remote processor, if failed return 0 as
> + * no data sent
> + */
> + ret = rpmsg_trysendto(cport->d_ept, tmpbuf, msg_size, cport->data_dst);

data of rpmsg_trysendto is not const. OK, you seem you need to change
that first, I see no blocker for that.

> + kfree(tmpbuf);
> + if (ret) {
> + dev_dbg(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
> + return 0;
> + }
> +
> + return msg_size;
> +}
> +
> +static int rpmsg_tty_write_room(struct tty_struct *tty)
> +{
> + struct rpmsg_tty_port *cport = tty->driver_data;
> +
> + return cport->cts ? rpmsg_get_mtu(cport->rpdev->ept) : 0;

With if, this would be more readable, IMO.

> +}
...> +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);

You should return ERR_PTR(cport->id) instead. It might be ENOMEM too.

> + }
> +
> + return cport;
> +}
...
> +static int rpmsg_tty_port_activate(struct tty_port *p, struct tty_struct *tty)
> +{
> + p->low_latency = (p->flags & ASYNC_LOW_LATENCY) ? 1 : 0;
> +
> + /* Allocate the buffer we use for writing data */

Where exactly -- am I missing something?

> + 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 int rpmsg_tty_probe(struct rpmsg_device *rpdev)
> +{
> + struct rpmsg_tty_port *cport;
> + struct device *dev = &rpdev->dev;
> + struct rpmsg_channel_info chinfo;
> + 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);
> + }
> +
> + if (!strncmp(rpdev->id.name, TTY_CH_NAME_WITH_CTS,
> + sizeof(TTY_CH_NAME_WITH_CTS))) {

sizeof of a string feels unnatural, but will work in this case. Can a
compiler optimize strlen of a static string?

> + /*
> + * the default endpoint is used for control. Create a second
> + * endpoint for the data that would be exchanges trough control
> + * endpoint. address of the data endpoint will be provided with
> + * the cts state
> + */
> + cport->cs_ept = rpdev->ept;
> + cport->data_dst = RPMSG_ADDR_ANY;
> +
> + strscpy(chinfo.name, TTY_CH_NAME_WITH_CTS, sizeof(chinfo.name));
> + chinfo.src = RPMSG_ADDR_ANY;
> + chinfo.dst = RPMSG_ADDR_ANY;
> +
> + cport->d_ept = rpmsg_create_ept(rpdev, rpmsg_tty_cb, cport,
> + chinfo);
> + if (!cport->d_ept) {
> + dev_err(dev, "failed to create tty control channel\n");
> + ret = -ENOMEM;
> + goto err_r_cport;
> + }
> + dev_dbg(dev, "%s: creating data endpoint with address %#x\n",
> + __func__, cport->d_ept->addr);
> + } else {
> + /*
> + * TTY over rpmsg without CTS management the default endpoint
> + * is use for raw data transmission.
> + */
> + cport->cs_ept = NULL;
> + cport->cts = 1;
> + cport->d_ept = rpdev->ept;
> + cport->data_dst = rpdev->dst;
> + }
> +
> + tty_port_init(&cport->port);
> + cport->port.ops = &rpmsg_tty_port_ops;

I expected these two in rpmsg_tty_alloc_cport.

> +
> + 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;
> + }
> +
> + cport->rpdev = rpdev;
> +
> + dev_set_drvdata(dev, cport);
> +
> + dev_dbg(dev, "new channel: 0x%x -> 0x%x : ttyRPMSG%d\n",
> + rpdev->src, rpdev->dst, cport->id);
> +
> + return 0;
> +
> +err_destroy:
> + tty_port_destroy(&cport->port);
> + if (cport->cs_ept)
> + rpmsg_destroy_ept(cport->d_ept);
> +err_r_cport:
> + rpmsg_tty_release_cport(cport);
> +
> + return ret;
> +}

thanks,
--
js
suse labs

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