FAILED: patch "[PATCH] xhci: dbc: honor usb transfer size boundaries." failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 30c9ae5ece8ecd69d36e6912c2c0896418f2468c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024102143-chevy-extras-add3@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 30c9ae5ece8ecd69d36e6912c2c0896418f2468c Mon Sep 17 00:00:00 2001
From: Mathias Nyman <[email protected]>
Date: Wed, 16 Oct 2024 17:00:00 +0300
Subject: [PATCH] xhci: dbc: honor usb transfer size boundaries.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Treat each completed full size write to /dev/ttyDBC0 as a separate usb transfer. Make sure the size of the TRBs matches the size of the tty write by first queuing as many max packet size TRBs as possible up to the last TRB which will be cut short to match the size of the tty write.

This solves an issue where userspace writes several transfers back to back via /dev/ttyDBC0 into a kfifo before dbgtty can find available request to turn that kfifo data into TRBs on the transfer ring.

The boundary between transfer was lost as xhci-dbgtty then turned everyting in the kfifo into as many 'max packet size' TRBs as possible.

DbC would then send more data to the host than intended for that transfer, causing host to issue a babble error.

Refuse to write more data to kfifo until previous tty write data is turned into properly sized TRBs with data size boundaries matching tty write size

index 8ec813b6e9fd..9dc8f4d8077c 100644
@@ -110,6 +110,7 @@ struct dbc_port {
 	struct tasklet_struct		push;
 
 	struct list_head		write_pool;
+	unsigned int			tx_boundary;
 
 	bool				registered;
 };