Re: correctly handling EPROTO

[Oliver Neukum <oneukum@suse.com>]

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On 12.03.26 15:21, Alan Stern wrote:
  
> There's a discussion about the same issue here:
> 
> 	https://bugzilla.kernel.org/show_bug.cgi?id=221184
> 
> See especially the later parts, starting with comment #28.

Well, that is fascinating, but not necessarily in a comfortable
way. It seems to me that for all drivers to care about the
exact details of getting which toggle back into sync is not
a viable strategy. This I'd say, when in doubt, clear a halt.

	Regards
		Oliver

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From fc7a673c780e8eaf08a529938e70ad00a9edd7b3 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@suse.com>
Date: Thu, 12 Mar 2026 12:29:23 +0100
Subject: [PATCH] usb: class: cdc-wdm handle EPROTO on interrupt endpoint

Under some conditions -EPROTO requires a halt to be cleared.
This is too complicated to get optimal. We should not even
try. Hence the sane strategy is to clear a halt on
-EPROTO and directly retry for everything but a known
disconnect.

Signed-off-by: Oliver Neukum <oneukum@suse.com>

eproto
---
 drivers/usb/class/cdc-wdm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 9185295f5376..cfb31a8145ff 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -265,13 +265,14 @@ static void wdm_int_callback(struct urb *urb)
 		case -ECONNRESET:
 			return; /* unplug */
 		case -EPIPE:
+		case -EPROTO:
 			set_bit(WDM_INT_STALL, &desc->flags);
 			dev_err(&desc->intf->dev, "Stall on int endpoint\n");
 			goto sw; /* halt is cleared in work */
 		default:
 			dev_err_ratelimited(&desc->intf->dev,
 				"nonzero urb status received: %d\n", status);
-			break;
+			goto exit;
 		}
 	}
 
-- 
2.53.0