This is a note to let you know that I've just added the patch titled usb: gadget: f_uac2: always increase endpoint max_packet_size by one audio slot to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: usb-gadget-f_uac2-always-increase-endpoint-max_packet_size-by-one-audio-slot.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 789ea77310f0200c84002884ffd628e2baf3ad8a Mon Sep 17 00:00:00 2001 From: Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx> Date: Mon, 1 Mar 2021 13:49:31 +0200 Subject: usb: gadget: f_uac2: always increase endpoint max_packet_size by one audio slot From: Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx> 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@xxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> #v4.3+ Signed-off-by: Ruslan Bilovol <ruslan.bilovol@xxxxxxxxx> Link: https://lore.kernel.org/r/1614599375-8803-2-git-send-email-ruslan.bilovol@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -482,7 +482,7 @@ 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)); Patches currently in stable-queue which might be from ruslan.bilovol@xxxxxxxxx are queue-4.19/usb-gadget-f_uac1-stop-playback-on-function-disable.patch queue-4.19/usb-gadget-f_uac2-always-increase-endpoint-max_packet_size-by-one-audio-slot.patch