From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Ruslan Bilovol ruslan.bilovol@gmail.com
commit 789ea77310f0200c84002884ffd628e2baf3ad8a upstream.
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 Link: https://lore.kernel.org/r/1614599375-8803-2-git-send-email-ruslan.bilovol@gm... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/gadget/function/f_uac2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/usb/gadget/function/f_uac2.c +++ b/drivers/usb/gadget/function/f_uac2.c @@ -486,7 +486,7 @@ static int set_ep_max_packet_size(const }
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));