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SubjectRe: [PATCH 2/2] tty: add rpmsg driver
On Thu, Mar 21, 2019 at 04:47:19PM +0100, Fabien Dessenne 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>
> ---
> drivers/tty/Kconfig | 9 ++
> drivers/tty/Makefile | 1 +
> drivers/tty/rpmsg_tty.c | 309 ++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 319 insertions(+)
> create mode 100644 drivers/tty/rpmsg_tty.c

> +static int rpmsg_tty_write(struct tty_struct *tty, const unsigned char *buf,
> + int total)
> +{
> + int count, ret = 0;
> + const unsigned char *tbuf;
> + struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index);
> + struct rpmsg_device *rpdev;
> + int msg_size;
> +
> + if (!cport) {
> + dev_err(tty->dev, "cannot get cport\n");
> + return -ENODEV;
> + }
> +
> + rpdev = cport->rpdev;
> +
> + dev_dbg(&rpdev->dev, "%s: send message from tty->index = %d\n",
> + __func__, tty->index);
> +
> + if (!buf) {
> + dev_err(&rpdev->dev, "buf shouldn't be null.\n");
> + return -ENOMEM;
> + }
> +
> + msg_size = rpmsg_get_buf_payload_size(rpdev->ept);
> + if (msg_size < 0)
> + return msg_size;
> +
> + count = total;
> + tbuf = buf;
> + do {
> + /* send a message to our remote processor */
> + ret = rpmsg_send(rpdev->ept, (void *)tbuf,
> + min(count, msg_size));

Just a drive-by comment; it looks like rpmsg_send() may block, but
the tty-driver write() callback must never sleep.

> + if (ret) {
> + dev_err(&rpdev->dev, "rpmsg_send failed: %d\n", ret);
> + return ret;
> + }
> +
> + if (count > msg_size) {
> + count -= msg_size;
> + tbuf += msg_size;
> + } else {
> + count = 0;
> + }
> + } while (count > 0);
> +
> + return total;
> +}

Johan

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