...
> > --- /dev/null
> > +++ b/drivers/net/can/lin.c
> ...> +static int lin_create_sysfs_id_files(struct net_device *ndev)
> > +{
> > + struct lin_device *ldev = netdev_priv(ndev);
> > + struct kobj_attribute *attr;
> > + int ret;
> > +
> > + for (int id = 0; id < LIN_NUM_IDS; id++) {
> > + ldev->sysfs_entries[id].ldev = ldev;
> > + attr = &ldev->sysfs_entries[id].attr;
> > + attr->attr.name = kasprintf(GFP_KERNEL, "%02x", id);
> > + if (!attr->attr.name)
> > + return -ENOMEM;
> > + attr->attr.mode = 0644;
> > + attr->show = lin_identifier_show;
> > + attr->store = lin_identifier_store;
> > +
> > + sysfs_attr_init(&attr->attr);
> > + ret = sysfs_create_file(ldev->lin_ids_kobj, &attr->attr);
> > + if (ret) {
> > + kfree(attr->attr.name);
> > + kfree(attr);
>
> Is the latter kfree() right? It appears not.
Thanks for the catch, it's wrong and will be removed in v2.
>
> > + return -ENOMEM;
> > + }
> > + }
> > +
> > + return 0;
> > +}
> ...
> > +static void lin_tx_work_handler(struct work_struct *ws)
> > +{
> > + struct lin_device *ldev = container_of(ws, struct lin_device,
> > + tx_work);
> > + struct net_device *ndev = ldev->ndev;
> > + struct canfd_frame *cfd;
> > + struct lin_frame lf;
> > +
> > + ldev->tx_busy = true;
>
> How is this store protected against reordering/race conditions?
Falsely it is not, like in mcp251x.c I'll add a mutex.
>
> > +
> > + cfd = (struct canfd_frame *)ldev->tx_skb->data;
> > + lf.checksum_mode = (cfd->can_id & LIN_ENHANCED_CKSUM_FLAG) ?
> > + LINBUS_ENHANCED : LINBUS_CLASSIC;
> > + lf.lin_id = (u8)(cfd->can_id & LIN_ID_MASK);
>
> Why is that cast necessary?
It's not.
>
> > + lf.len = min(cfd->len, LIN_MAX_DLEN);
> > + memcpy(lf.data, cfd->data, lf.len);
> > +
> > + ret = ldev->ldev_ops->ldo_tx(ldev, &lf);
> > + if (ret) {
> > + DEV_STATS_INC(ndev, tx_dropped);
> > + netdev_err_once(ndev, "transmission failure %d\n", ret);
> > + goto lin_tx_out;
>
> Where is this label?
In a later patch, let me fix the patchset accordingly.
>
> > + }
> > +
> > + DEV_STATS_INC(ndev, tx_packets);
> > + DEV_STATS_ADD(ndev, tx_bytes, lf.len);
> > + ldev->tx_busy = false;
>
> The same as above.
OK
>
> > + netif_wake_queue(ndev);
> > +}
> > +
> > +static netdev_tx_t lin_start_xmit(struct sk_buff *skb,
> > + struct net_device *ndev)
> > +{
> > + struct lin_device *ldev = netdev_priv(ndev);
> > +
> > + if (ldev->tx_busy)
> > + return NETDEV_TX_BUSY;
>
> And here too.
OK
>
> > +
> > + netif_stop_queue(ndev);
> > + ldev->tx_skb = skb;
> > + queue_work(ldev->wq, &ldev->tx_work);
> > +
> > + return NETDEV_TX_OK;
> > +}
> ...
> > +u8 lin_get_checksum(u8 pid, u8 n_of_bytes, const u8 *bytes,
> > + enum lin_checksum_mode cm)
> > +{
> > + uint csum = 0;
>
> Is "uint" of the preffered types in the kernel?
OK, no sysv 'uint', will be changed in another patch too
>
> > + int i;
> > +
> > + if (cm == LINBUS_ENHANCED)
> > + csum += pid;
> > +
> > + for (i = 0; i < n_of_bytes; i++) {
> > + csum += bytes[i];
> > + if (csum > 255)
> > + csum -= 255;
> > + }
> > +
> > + return (u8)(~csum & 0xff);
>
> Unnecessary cast?
Yes
>
> > +}
>
>
> > +int lin_rx(struct lin_device *ldev, const struct lin_frame *lf)
> > +{
> > + struct net_device *ndev = ldev->ndev;
> > + struct can_frame *cf;
> > + struct sk_buff *skb;
> > + int ret;
> > +
> > + if (!ndev)
> > + return -ENODEV;
>
> Is this racy or is this only a sanity check?
Just beeing cautious, I guess it can be removed
>
> > + netdev_dbg(ndev, "id:%02x, len:%u, data:%*ph, checksum:%02x (%s)\n",
> > + lf->lin_id, lf->len, lf->len, lf->data, lf->checksum,
> > + lf->checksum_mode ? "enhanced" : "classic");
> > +
> > + ret = lin_bump_rx_err(ldev, lf);
> > + if (ret) {
> > + DEV_STATS_INC(ndev, rx_dropped);
> > + return ret;
> > + }
> > +
> > + skb = alloc_can_skb(ndev, &cf);
> > + if (unlikely(!skb)) {
> > + DEV_STATS_INC(ndev, rx_dropped);
> > + return -ENOMEM;
> > + }
> > +
> > + cf->can_id = lf->lin_id;
> > + cf->len = min(lf->len, LIN_MAX_DLEN);
> > + memcpy(cf->data, lf->data, cf->len);
> > +
> > + DEV_STATS_INC(ndev, rx_packets);
> > + DEV_STATS_ADD(ndev, rx_bytes, cf->len);
> > +
> > + netif_receive_skb(skb);
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(lin_rx);
> > +
> > +static int lin_set_bittiming(struct net_device *ndev)
> > +{
> > + struct lin_device *ldev = netdev_priv(ndev);
> > + unsigned int bitrate;
> > + int ret;
> > +
> > + bitrate = ldev->can.bittiming.bitrate;
> > + ret = ldev->ldev_ops->update_bitrate(ldev, bitrate);
> > +
> > + return ret;
>
> No need for ret then.
Compact code, sure, will get adapted
>
> > +}
> > +
> > +static const u32 lin_bitrate[] = { 1200, 2400, 4800, 9600, 19200 };
> > +
> > +struct lin_device *register_lin(struct device *dev,
> > + const struct lin_device_ops *ldops)
> > +{
> > + struct net_device *ndev;
> > + struct lin_device *ldev;
> > + int ret;
> > +
> > + if (!ldops || !ldops->ldo_tx || !ldops->update_bitrate) {
> > + netdev_err(ndev, "missing mandatory lin_device_ops\n");
> > + return ERR_PTR(-EOPNOTSUPP);
>
> Would EINVAL fit better?
no preference over the other, will use EINVAL
>
> > + }
> > +
> > + ndev = alloc_candev(sizeof(struct lin_device), 1);
> > + if (!ndev)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + ldev = netdev_priv(ndev);
> > +
> > + ldev->ldev_ops = ldops;
> > + ndev->netdev_ops = &lin_netdev_ops;
> > + ndev->flags |= IFF_ECHO;
> > + ndev->mtu = CANFD_MTU;
> > + ldev->can.bittiming.bitrate = LIN_DEFAULT_BAUDRATE;
> > + ldev->can.ctrlmode = CAN_CTRLMODE_LIN;
> > + ldev->can.ctrlmode_supported = 0;
> > + ldev->can.bitrate_const = lin_bitrate;
> > + ldev->can.bitrate_const_cnt = ARRAY_SIZE(lin_bitrate);
> > + ldev->can.do_set_bittiming = lin_set_bittiming;
> > + ldev->ndev = ndev;
> > + ldev->dev = dev;
> > +
> > + SET_NETDEV_DEV(ndev, dev);
> > +
> > + ret = lin_set_bittiming(ndev);
> > + if (ret) {
> > + netdev_err(ndev, "set bittiming failed\n");
> > + goto exit_candev;
> > + }
> > +
> > + ret = register_candev(ndev);
> > + if (ret)
> > + goto exit_candev;
> > +
> > + ldev->lin_ids_kobj = kobject_create_and_add("lin_ids", &ndev->dev.kobj);
> > + if (!ldev->lin_ids_kobj) {
> > + netdev_err(ndev, "Failed to create sysfs directory\n");
> > + ret = -ENOMEM;
> > + goto exit_unreg;
> > + }
> > +
> > + ret = lin_create_sysfs_id_files(ndev);
> > + if (ret) {
> > + netdev_err(ndev, "Failed to create sysfs entry: %d\n", ret);
> > + goto exit_kobj_put;
> > + }
> > +
> > + ldev->wq = alloc_workqueue(dev_name(dev), WQ_FREEZABLE | WQ_MEM_RECLAIM,
> > + 0);
>
> It would be worth noting why you need your own WQ.
I'll add a comment stating:
/* Use workqueue as tx over USB/SPI/... may sleep */
>
> > + if (!ldev->wq)
> > + goto exit_rm_files;
> > +
> > + INIT_WORK(&ldev->tx_work, lin_tx_work_handler);
> > +
> > + netdev_info(ndev, "LIN initialized.\n");
> > +
> > + return ldev;
> > +
> > +exit_rm_files:
> > + lin_remove_sysfs_id_files(ndev);
> > +exit_kobj_put:
> > + kobject_put(ldev->lin_ids_kobj);
> > +exit_unreg:
> > + unregister_candev(ndev);
> > +exit_candev:
> > + free_candev(ndev);
> > + return ERR_PTR(ret);
> > +}
> > +EXPORT_SYMBOL_GPL(register_lin);
> > +
> > +void unregister_lin(struct lin_device *ldev)
> > +{
> > + struct net_device *ndev = ldev->ndev;
> > +
> > + lin_remove_sysfs_id_files(ndev);
> > + kobject_put(ldev->lin_ids_kobj);
> > + unregister_candev(ndev);
> > + destroy_workqueue(ldev->wq);
> > + free_candev(ndev);
> > +}
> > +EXPORT_SYMBOL_GPL(unregister_lin);
> > +
> > +MODULE_LICENSE("GPL");
> > +MODULE_AUTHOR("Christoph Fritz <christoph.fritz@xxxxxxxxx>");
> > +MODULE_DESCRIPTION("LIN bus to CAN glue driver");
> > diff --git a/include/net/lin.h b/include/net/lin.h
> > new file mode 100644
> > index 0000000000000..2fe16e142db96
> > --- /dev/null
> > +++ b/include/net/lin.h
> > @@ -0,0 +1,97 @@
> > +/* SPDX-License-Identifier: GPL-2.0+ */
> > +/* Copyright (C) 2024 hexDEV GmbH - https://hexdev.de */
> > +
> > +#ifndef _NET_LIN_H_
> > +#define _NET_LIN_H_
> > +
> > +#include <linux/can/dev.h>
> > +#include <linux/device.h>
> > +
> > +#define LIN_NUM_IDS 64
> > +#define LIN_HEADER_SIZE 3
> > +#define LIN_MAX_DLEN 8
> > +
> > +#define LIN_MAX_BAUDRATE 20000
> > +#define LIN_MIN_BAUDRATE 1000
> > +#define LIN_DEFAULT_BAUDRATE 9600
> > +#define LIN_SYNC_BYTE 0x55
> > +
> > +#define LIN_ID_MASK 0x0000003FU
>
> GEN_MASK() ?
In the upcoming v2 I'll use:
#define LIN_ID_MASK GENMASK(5, 0)
>
> > +/* special ID descriptions for LIN */
> > +#define LIN_ENHANCED_CKSUM_FLAG 0x00000100U
> > +
> > +static const unsigned char lin_id_parity_tbl[] = {
>
> This ends up in every translation unit you include lin.h into. Bad.
This is also being used by a serial lin driver. But I guess most of the drivers have no need for this. Mhm, ... any ideas?
> And perhaps u8?
OK
>
> > + 0x80, 0xc0, 0x40, 0x00, 0xc0, 0x80, 0x00, 0x40,
> > + 0x00, 0x40, 0xc0, 0x80, 0x40, 0x00, 0x80, 0xc0,
> > + 0x40, 0x00, 0x80, 0xc0, 0x00, 0x40, 0xc0, 0x80,
> > + 0xc0, 0x80, 0x00, 0x40, 0x80, 0xc0, 0x40, 0x00,
> > + 0x00, 0x40, 0xc0, 0x80, 0x40, 0x00, 0x80, 0xc0,
> > + 0x80, 0xc0, 0x40, 0x00, 0xc0, 0x80, 0x00, 0x40,
> > + 0xc0, 0x80, 0x00, 0x40, 0x80, 0xc0, 0x40, 0x00,
> > + 0x40, 0x00, 0x80, 0xc0, 0x00, 0x40, 0xc0, 0x80,
> > +};
> > +
> > +#define LIN_GET_ID(PID) ((PID) & LIN_ID_MASK)
>
> FIELD_GET() ?
In the upcoming v2 I'll use:
#define LIN_GET_ID(PID) FIELD_GET(LIN_ID_MASK, PID)
>
> > +#define LIN_FORM_PID(ID) (LIN_GET_ID(ID) | \
> > + lin_id_parity_tbl[LIN_GET_ID(ID)])
> > +#define LIN_GET_PARITY(PID) ((PID) & ~LIN_ID_MASK)
> > +#define LIN_CHECK_PID(PID) (LIN_GET_PARITY(PID) == \
> > + LIN_GET_PARITY(LIN_FORM_PID(PID)))
>
Thanks for the feedback
-- Christoph
