Hi,
On Fri, Jun 23, 2017 at 5:54 PM, Bin Meng <bmeng...@gmail.com> wrote:
> The only work we need do in usb_setup_descriptor() is to initialize
> dev->descriptor.bMaxPacketSize0, when do_read is false. Other steps
> are the same as do_read being true.
>
> While we are here, update the comment block to be within 80 cols.
>
> Signed-off-by: Bin Meng <bmeng...@gmail.com>
> ---
>
> common/usb.c | 40 ++++++++++++++++++----------------------
> 1 file changed, 18 insertions(+), 22 deletions(-)
>
> diff --git a/common/usb.c b/common/usb.c
> index 15e1e4c..293d968 100644
> --- a/common/usb.c
> +++ b/common/usb.c
> @@ -962,37 +962,33 @@ static int usb_setup_descriptor(struct usb_device *dev,
> bool do_read)
> * some more, or keeps on retransmitting the 8 byte header.
> */
>
> - if (dev->speed == USB_SPEED_LOW) {
> - dev->descriptor.bMaxPacketSize0 = 8;
> - dev->maxpacketsize = PACKET_SIZE_8;
> - } else {
> - dev->descriptor.bMaxPacketSize0 = 64;
> - dev->maxpacketsize = PACKET_SIZE_64;
> - }
> - dev->epmaxpacketin[0] = dev->descriptor.bMaxPacketSize0;
> - dev->epmaxpacketout[0] = dev->descriptor.bMaxPacketSize0;
> -
> if (do_read) {
> int err;
>
> /*
> - * Validate we've received only at least 8 bytes, not that
> we've
> - * received the entire descriptor. The reasoning is:
> - * - The code only uses fields in the first 8 bytes, so
> that's all we
> - * need to have fetched at this stage.
> - * - The smallest maxpacket size is 8 bytes. Before we know
> the actual
> - * maxpacket the device uses, the USB controller may only
> accept a
> - * single packet. Consequently we are only guaranteed to
> receive 1
> - * packet (at least 8 bytes) even in a non-error case.
> + * Validate we've received only at least 8 bytes, not that
> + * we've received the entire descriptor. The reasoning is:
> + * - The code only uses fields in the first 8 bytes, so that's
> + * all we need to have fetched at this stage.
> + * - The smallest maxpacket size is 8 bytes. Before we know
> + * the actual maxpacket the device uses, the USB controller
> + * may only accept a single packet. Consequently we are only
> + * guaranteed to receive 1 packet (at least 8 bytes) even in
> + * a non-error case.
> *
> - * At least the DWC2 controller needs to be programmed with
> the number
> - * of packets in addition to the number of bytes. A request
> for 64
> - * bytes of data with the maxpacket guessed as 64 (above)
> yields a
> - * request for 1 packet.
> + * At least the DWC2 controller needs to be programmed with
> + * the number of packets in addition to the number of bytes.
> + * A request for 64 bytes of data with the maxpacket guessed
> + * as 64 (above) yields a request for 1 packet.
> */
> err = get_descriptor_len(dev, 64, 8);
> if (err)
> return err;
> + } else {
> + if (dev->speed == USB_SPEED_LOW)
> + dev->descriptor.bMaxPacketSize0 = 8;
> + else
> + dev->descriptor.bMaxPacketSize0 = 64;
> }
>
> dev->epmaxpacketin[0] = dev->descriptor.bMaxPacketSize0;
> --
For some reason that I don't understand, this patch breaks EHCI.
dev->maxpacketsize is equal to zero with this patch, which leads to a
'divide error' exception in ehci_submit_async(). Not sure if anyone
has some hints?
For now, I will just drop this patch in v2. This needs be further revisited.
Regards,
Bin
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