linux-kernel - Re: [PATCH V2] can: usb: f81604: add Fintek F81604 support

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Message-ID: <CAMZ6Rq+xSCLe8CYm6K0CyPABo-Gzrt-JUO7_XGgXum+G8k5FCQ@mail.gmail.com>
Date:   Thu, 23 Mar 2023 14:54:04 +0900
From:   Vincent MAILHOL <mailhol.vincent@...adoo.fr>
To:     Peter Hong <peter_hong@...tek.com.tw>
Cc:     wg@...ndegger.com, mkl@...gutronix.de,
        michal.swiatkowski@...ux.intel.com, Steen.Hegelund@...rochip.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, frank.jungclaus@....eu,
        linux-kernel@...r.kernel.org, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, hpeter+linux_kernel@...il.com
Subject: Re: [PATCH V2] can: usb: f81604: add Fintek F81604 support

Le jeu. 23 mars 2023 à 14:14, Peter Hong <peter_hong@...tek.com.tw> a écrit :
>
> Hi Vincent,
>
> Vincent MAILHOL 於 2023/3/21 下午 11:50 寫道:
> >> +static netdev_tx_t f81604_start_xmit(struct sk_buff *skb,
> >> +                                    struct net_device *netdev)
> >> +{
> >> +       struct can_frame *cf = (struct can_frame *)skb->data;
> >> +       struct f81604_port_priv *priv = netdev_priv(netdev);
> >> +       struct net_device_stats *stats = &netdev->stats;
> >> +       int status;
> >> +       u8 *ptr;
> >> +       u32 id;
> >> +
> >> +       if (can_dropped_invalid_skb(netdev, skb))
> >> +               return NETDEV_TX_OK;
> >> +
> >> +       netif_stop_queue(netdev);
> >> +
> >> +       ptr = priv->bulk_write_buffer;
> >> +       memset(ptr, 0, F81604_DATA_SIZE);
> >> +
> >> +       ptr[0] = F81604_CMD_DATA;
> >> +       ptr[1] = min_t(u8, cf->can_dlc & 0xf, 8);
> >> +
> >> +       if (cf->can_id & CAN_EFF_FLAG) {
> >> +               id = (cf->can_id & CAN_ERR_MASK) << 3;
> >> +               ptr[1] |= F81604_EFF_BIT;
> >> +               ptr[2] = (id >> 24) & 0xff;
> >> +               ptr[3] = (id >> 16) & 0xff;
> >> +               ptr[4] = (id >> 8) & 0xff;
> >> +               ptr[5] = (id >> 0) & 0xff;
> >> +               memcpy(&ptr[6], cf->data, ptr[1]);
> > Rather than manipulating an opaque u8 array, please declare a
> > structure with explicit names.
>
> I had try to declare a struct like below and refactoring code :
>
> struct f81604_bulk_data {
>      u8 cmd;
>      u8 dlc;
>
>      union {
>          struct {
>              u8 id1, id2;
>              u8 data[CAN_MAX_DLEN];
>          } sff;
>
>          struct {
>              u8 id1, id2, id3, id4;
>              u8 data[CAN_MAX_DLEN];
>          } eff;
>      };
> } __attribute__((packed));
>
> This struct can used in TX/RX bulk in/out. Is it ok?

That's nearly it. It is better to declare the struct sff and eff
separately. Also, do not split the id in bytes. Declare it as a little
endian using the __le16 and __le32 types.

Something like this (I let you adjust):

  struct f81604_sff {
          __le16 id:
          u8 data[CAN_MAX_DLEN];
  } __attribute__((packed));

  struct f81604_eff {
          __le32 id;
          u8 data[CAN_MAX_DLEN];
  } __attribute__((packed));

  struct f81604_bulk_data {
          u8 cmd;
          u8 dlc;

          union {
                  struct f81604_sff sff;
                  struct f81604_eff eff;
           };
  } __attribute__((packed));

The __le16 field should be manipulated using cpu_to_leXX() and
leXX_to_cpu() if the field is aligned, if not, it should be
manipulated using {get|set}_unaligned_leXX() (where XX represents the
size in bits).

Also, f81604_bulk_data->dlc is not only a DLC but also carries the
F81604_EFF_BIT flag, right? At least, add documentation to the
structure to clarify this point.

> > +static int f81604_prepare_urbs(struct net_device *netdev)
> > +{
> > +       static const u8 bulk_in_addr[F81604_MAX_DEV] = { 0x82, 0x84 };
> > +       static const u8 bulk_out_addr[F81604_MAX_DEV] = { 0x01, 0x03 };
> > +       static const u8 int_in_addr[F81604_MAX_DEV] = { 0x81, 0x83 };
> > +       struct f81604_port_priv *priv = netdev_priv(netdev);
> > +       int id = netdev->dev_id;
> > +       int i;
> > +
> > +       /* initialize to NULL for error recovery */
> > +       for (i = 0; i < F81604_MAX_RX_URBS; ++i)
> > +               priv->read_urb[i] = NULL;
> > priv was allocated with devm_kzalloc() so it should already be zeroed,
> > right? What is the purpose of this loop?
>
> This operation due to following condition:
>      f81604_open() -> f81604_close() -> f81604_open() failed.
>
> We had used  devm_kzalloc() in f81604_probe(), so first f81604_open() all
> pointers are NULL. But after f81604_close() then f81604_open() second
> times, the URB pointers are not NULLed, it'll makes error on 2nd
> f81604_open()
> with fail.

Makes sense, thanks for the clarification.

Then, please replace your loop by a memset(priv->read_urb, 0,
sizeof(priv->read_urb).

> >> +/* Called by the usb core when driver is unloaded or device is removed */
> >> +static void f81604_disconnect(struct usb_interface *intf)
> >> +{
> >> +       struct f81604_priv *priv = usb_get_intfdata(intf);
> >> +       int i;
> >> +
> >> +       for (i = 0; i < F81604_MAX_DEV; ++i) {
> >> +               if (!priv->netdev[i])
> >> +                       continue;
> >> +
> >> +               unregister_netdev(priv->netdev[i]);
> >> +               free_candev(priv->netdev[i]);
> >> +       }
> >   i> +}
>
> Is typo here?

Yes, please ignore.


Yours sincerely,
Vincent Mailhol