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SubjectRe: [PATCH v7 2/2] tty: add rpmsg driver
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On 3/25/20 9:45 AM, Jiri Slaby wrote:
> 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;

In this case i would prefer cport->cts = (msg->cts != 1);
for the conversion

>
>> + 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.

I created a temporary buffer to ensure that buffer to sent does not exceed the
MTU size.
But perhaps this is an useless protection as the rpmsg_tty_write_room already
return the MTU value, and so the 'len' variable can not be higher that value
returned by the write_room?

>
>> + 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?

in tty_port_alloc_xmit_buf. it's a copy past from mips_ejtag_fdc.c,
I will clean this line if it's confusing.

>
>> + 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?

I don't know if a compiler can do this...
what about replacing sizeof by strlen function?
i saw some code example that use strlen with static string...
(e.g https://elixir.bootlin.com/linux/latest/source/drivers/edac/edac_mc.c#L1193)


I will take into account all your other comments in may next version.

Thanks for the review,
Arnaud

>
>> + /*
>> + * 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,
>

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