As per UAC2 Audio Data Formats spec (2.3.1.1 USB Packets), if the sampling rate is a constant, the allowable variation of number of audio slots per virtual frame is +/- 1 audio slot.

It means that endpoint should be able to accept/send +1 audio slot.

Previous endpoint max_packet_size calculation code was adding sometimes +1 audio slot due to DIV_ROUND_UP behaviour which was rounding up to closest integer. However this doesn't work if the numbers are divisible.

It had no any impact with Linux hosts which ignore this issue, but in case of more strict Windows it caused rejected enumeration

Thus always add +1 audio slot to endpoint's max packet size

Fixes: 913e4a90b6f9 ("usb: gadget: f_uac2: finalize wMaxPacketSize according to bandwidth") Cc: Peter Chen peter.chen@freescale.com Cc: stable@vger.kernel.org #v4.3+ Signed-off-by: Ruslan Bilovol ruslan.bilovol@gmail.com --- drivers/usb/gadget/function/f_uac2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c index 740cb64..c62cccb 100644 --- a/drivers/usb/gadget/function/f_uac2.c +++ b/drivers/usb/gadget/function/f_uac2.c @@ -478,7 +478,7 @@ static int set_ep_max_packet_size(const struct f_uac2_opts *uac2_opts, }

max_size_bw = num_channels(chmask) * ssize * - DIV_ROUND_UP(srate, factor / (1 << (ep_desc->bInterval - 1))); + ((srate / (factor / (1 << (ep_desc->bInterval - 1)))) + 1); ep_desc->wMaxPacketSize = cpu_to_le16(min_t(u16, max_size_bw, max_size_ep));