Re: [PATCH v6 3/3] Bluetooth: NXP: Add protocol support for NXP Bluetooth chipsets

[Ilpo Järvinen]

On Mon, 6 Mar 2023, Neeraj sanjay kale wrote:

> Hi Ilpo,
> 
> Thank you for reviewing this patch. I have resolved most of your review comments in v7 patch, and I have some clarification inline below:

Further discussion below + I sent a few against v7.

 
> > > +static bool nxp_fw_change_baudrate(struct hci_dev *hdev, u16 req_len)
> > > +{
> > > +     struct btnxpuart_dev *nxpdev = hci_get_drvdata(hdev);
> > > +     struct nxp_bootloader_cmd nxp_cmd5;
> > > +     struct uart_config uart_config;
> > > +
> > > +     if (req_len == sizeof(nxp_cmd5)) {
> > > +             nxp_cmd5.header = __cpu_to_le32(5);
> > > +             nxp_cmd5.arg = 0;
> > > +             nxp_cmd5.payload_len = __cpu_to_le32(sizeof(uart_config));
> > > +             nxp_cmd5.crc = swab32(crc32_be(0UL, (char *)&nxp_cmd5,
> > > +                                            sizeof(nxp_cmd5) - 4));
> > 
> > swab32(crc32_be(...)) seems and odd construct instead of __cpu_to_le32().
> Earlier I had tried using __cpu_to_le32() but that did not work. The FW expects a swapped
> CRC value for it's header and payload data.

So the .crc member should be __be32 then?

> > > +     serdev_device_write_buf(nxpdev->serdev, (u8 *)&nxp_cmd7,
> > > + req_len);
> > 
> > Is it safe to assume req_len is small enough to not leak stack content?
> The chip requests chunk of FW data which is never more than 2048 bytes 
> at a time. 

Eh, sizeof(*nxp_cmd7) is 16 bytes!?! Are you sure that req_len given to 
serdev_device_write_buf() is not larger than 16 bytes?

> > > +static bool nxp_check_boot_sign(struct btnxpuart_dev *nxpdev) {
> > > +     int ret;
> > > +
> > > +     serdev_device_set_baudrate(nxpdev->serdev,
> > HCI_NXP_PRI_BAUDRATE);
> > > +     serdev_device_set_flow_control(nxpdev->serdev, 0);
> > > +     set_bit(BTNXPUART_CHECK_BOOT_SIGNATURE, &nxpdev->tx_state);
> > > +
> > > +     ret = wait_event_interruptible_timeout(nxpdev-
> > >check_boot_sign_wait_q,
> > > +                                            !test_bit(BTNXPUART_CHECK_BOOT_SIGNATURE,
> > > +                                                      &nxpdev->tx_state),
> > > +                                            msecs_to_jiffies(1000));
> > > +     if (ret == 0)
> > > +             return false;
> > > +     else
> > > +             return true;
> > 
> > How does does this handle -ERESTARTSYS? But this runs in nxp_setup() so is
> > that even relevant (I don't know).
> This function is waits for 1 second and checks if it is receiving any bootloader signatures
> over UART. If yes, it means FW download is needed. If no, it means FW is already present
> on the chip, and we skip FW download.

Okay, it seems your changes had a side-effect of addressing this.

> > > +static int nxp_enqueue(struct hci_dev *hdev, struct sk_buff *skb) {
> > > +     struct btnxpuart_dev *nxpdev = hci_get_drvdata(hdev);
> > > +     struct ps_data *psdata = nxpdev->psdata;
> > > +     struct hci_command_hdr *hdr;
> > > +     u8 param[MAX_USER_PARAMS];
> > > +
> > > +     if (!nxpdev || !psdata)
> > > +             goto free_skb;
> > > +
> > > +     /* if vendor commands are received from user space (e.g. hcitool),
> > update
> > > +      * driver flags accordingly and ask driver to re-send the command to
> > FW.
> > > +      */
> > > +     if (bt_cb(skb)->pkt_type == HCI_COMMAND_PKT &&
> > > + !psdata->driver_sent_cmd) {
> > 
> > Should this !psdata->driver_sent_cmd do something else than end up into a
> > place labelled send_skb. Maybe return early (or free skb + return)?
> > There's a comment elsewhere stating: "set flag to prevent re-sending
> > command in nxp_enqueue."
> I'm sorry if the comment was misleading. This flag is set to prevent nxp_enqueue() from
> Parsing the command parameters again, and calling hci_cmd_sync_queue() again.
> The commands sent from user space, as well as the commands sent by __hci_cmd_sync(),
> both endup in nxp_enqueue().
> Hope this helps!

Okay, makes sense now and the logic is also clearer now. However, the
brace blocks you added into those cases in bxp_enqueue() you should try to 
remove. I realize you do it to avoid name collisions because you reused 
param in each but they introduced these ugly constructs:
	case XX:
		{
			...
			goto free_skb;
		}
		break;

-- 
 i.