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

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Date:   Thu, 23 Mar 2023 13:11:20 +0800
From:   Peter Hong <peter_hong@...tek.com.tw>
To:     Vincent MAILHOL <mailhol.vincent@...adoo.fr>
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

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?

> +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.

>> +/* 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?

Thanks.