Re: [PATCH v2 07/12] can: Add support for serdev LIN adapters

[Jiri Slaby <jirislaby@kernel.org>]

On 02. 05. 24, 9:55, Christoph Fritz wrote:
> This commit introduces LIN-Bus support for UART devices equipped with
> LIN transceivers, utilizing the Serial Device Bus (serdev) interface.
> 
> For more details on an adapter, visit: https://hexdev.de/hexlin#tty
...
> --- /dev/null
> +++ b/drivers/net/can/lin-serdev.c
> @@ -0,0 +1,514 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/* Copyright (C) 2024 hexDEV GmbH - https://hexdev.de */
> +
> +#include <linux/module.h>
> +#include <linux/wait.h>
> +#include <linux/init.h>
> +#include <linux/errno.h>
> +#include <linux/string.h>
> +#include <linux/kernel.h>

What do you need kernel.h for? You should explicitly require what you 
need (you apparently do), so kernel.h should not be needed.

> +#include <net/lin.h>
> +#include <linux/of.h>
> +#include <linux/serdev.h>
> +#include <linux/slab.h>
> +#include <linux/kfifo.h>
> +#include <linux/workqueue.h>
> +#include <linux/tty.h>

Might be eaier to maintain if you sort them.

> +#define LINSER_SAMPLES_PER_CHAR		10
> +#define LINSER_TX_BUFFER_SIZE		11
> +#define LINSER_RX_FIFO_SIZE		256
> +#define LINSER_PARSE_BUFFER		24
> +
> +struct linser_rx {
> +	u8 data;
> +	u8 flag;
> +};
> +
> +enum linser_rx_status {
> +	NEED_MORE = -1,
> +	MODE_OK = 0,
> +	NEED_FORCE,
> +};
> +
> +struct linser_priv {
> +	struct lin_device *lin_dev;
> +	struct serdev_device *serdev;
> +	DECLARE_KFIFO_PTR(rx_fifo, struct linser_rx);
> +	struct delayed_work rx_work;
> +	ulong break_usleep_min;
> +	ulong break_usleep_max;
> +	ulong post_break_usleep_min;
> +	ulong post_break_usleep_max;
> +	ulong force_timeout_jfs;

The same as for uint :)

> +	struct lin_responder_answer respond_answ[LIN_NUM_IDS];
> +	struct mutex resp_lock; /* protects respond_answ */
> +	bool is_stopped;
> +};
...
> +static void linser_derive_timings(struct linser_priv *priv, u16 bitrate)
> +{
> +	unsigned long break_baud = (bitrate * 2) / 3;
> +	unsigned long timeout_us;
> +

Are those 1000000UL USEC_PER_SEC?

> +	priv->break_usleep_min = (1000000UL * LINSER_SAMPLES_PER_CHAR) /
> +				 break_baud;
> +	priv->break_usleep_max = priv->break_usleep_min + 50;
> +	priv->post_break_usleep_min = (1000000UL * 1 /* 1 bit */) / break_baud;
> +	priv->post_break_usleep_max = priv->post_break_usleep_min + 30;
> +
> +	timeout_us = DIV_ROUND_CLOSEST(1000000UL * 256 /* bit */, bitrate);
> +	priv->force_timeout_jfs = usecs_to_jiffies(timeout_us);
> +}
...
> +static bool linser_tx_frame_as_responder(struct linser_priv *priv, u8 id)
> +{
> +	struct lin_responder_answer *answ = &priv->respond_answ[id];
> +	struct serdev_device *serdev = priv->serdev;
> +	u8 buf[LINSER_TX_BUFFER_SIZE];
> +	u8 checksum, count, n;
> +	ssize_t write_len;
> +
> +	mutex_lock(&priv->resp_lock);
> +
> +	if (!answ->is_active)
> +		goto unlock_and_exit_false;
> +
> +	if (answ->is_event_frame) {
> +		struct lin_responder_answer *e_answ;
> +
> +		e_answ = &priv->respond_answ[answ->event_associated_id];
> +		n = min(e_answ->lf.len, LIN_MAX_DLEN);
> +		if (memcmp(answ->lf.data, e_answ->lf.data, n) != 0) {
> +			memcpy(answ->lf.data, e_answ->lf.data, n);
> +			checksum = lin_get_checksum(LIN_FORM_PID(answ->lf.lin_id),
> +						    n, e_answ->lf.data,
> +						    answ->lf.checksum_mode);
> +			answ = e_answ;
> +		} else {
> +			goto unlock_and_exit_false;

Can't you simply use guard(mutex) above and avoid the error-prone 
gotos/cleanup completely?

> +		}
> +	} else {
> +		checksum = answ->lf.checksum;
> +	}
> +
> +	count = min(answ->lf.len, LIN_MAX_DLEN);
> +	memcpy(&buf[0], answ->lf.data, count);
> +	buf[count] = checksum;
> +
> +	mutex_unlock(&priv->resp_lock);
> +
> +	write_len = serdev_device_write(serdev, buf, count + 1, 0);
> +	if (write_len < count + 1)
> +		return false;
> +
> +	serdev_device_wait_until_sent(serdev, 0);
> +
> +	return true;
> +
> +unlock_and_exit_false:
> +	mutex_unlock(&priv->resp_lock);
> +	return false;
> +}
> +
> +static void linser_pop_fifo(struct linser_priv *priv, size_t n)
> +{
> +	struct serdev_device *serdev = priv->serdev;
> +	struct linser_rx dummy;
> +	size_t ret, i;
> +
> +	for (i = 0; i < n; i++) {
> +		ret = kfifo_out(&priv->rx_fifo, &dummy, 1);

Does kfifo_skip() not work for records? (I added it recently for serial.)

> +		if (ret != 1) {
> +			dev_err(&serdev->dev, "Failed to pop from FIFO\n");
> +			break;
> +		}
> +	}
> +}


thanks,
-- 
js
suse labs