FAILED: patch "[PATCH] usb: usbtmc: Fix read_stb function and get_stb ioctl" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x acb3dac2805d3342ded7dbbd164add32bbfdf21c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025061707-conceded-outwit-2f2f@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From acb3dac2805d3342ded7dbbd164add32bbfdf21c Mon Sep 17 00:00:00 2001
From: Dave Penkler <[email protected]>
Date: Wed, 21 May 2025 14:16:55 +0200
Subject: [PATCH] usb: usbtmc: Fix read_stb function and get_stb ioctl

The usbtmc488_ioctl_read_stb function relied on a positive return from usbtmc_get_stb to reset the srq condition in the driver. The USBTMC_IOCTL_GET_STB case tested for a positive return to return the stb to the user.

Commit: <cac01bd178d6> ("usb: usbtmc: Fix erroneous get_stb ioctl error returns") changed the return value of usbtmc_get_stb to 0 on success instead of returning the value of usb_control_msg which is positive in the normal case. This change caused the function usbtmc488_ioctl_read_stb and the USBTMC_IOCTL_GET_STB ioctl to no longer function correctly.

Change the test in usbtmc488_ioctl_read_stb to test for failure first and return the failure code immediately.
Change the test for the USBTMC_IOCTL_GET_STB ioctl to test for 0 instead of a positive value.

index 740d2d2b19fb..08511442a27f 100644
@@ -563,14 +563,15 @@ static int usbtmc488_ioctl_read_stb(struct usbtmc_file_data *file_data,
 
 	rv = usbtmc_get_stb(file_data, &stb);
 
-	if (rv > 0) {
-		srq_asserted = atomic_xchg(&file_data->srq_asserted,
-					srq_asserted);
-		if (srq_asserted)
-			stb |= 0x40; /* Set RQS bit */
+	if (rv < 0)
+		return rv;
+
+	srq_asserted = atomic_xchg(&file_data->srq_asserted, srq_asserted);
+	if (srq_asserted)
+		stb |= 0x40; /* Set RQS bit */
+
+	rv = put_user(stb, (__u8 __user *)arg);
 
-		rv = put_user(stb, (__u8 __user *)arg);
-	}
 	return rv;
 
 }

@@ -2199,7 +2200,7 @@ static long usbtmc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
 	case USBTMC_IOCTL_GET_STB:
 		retval = usbtmc_get_stb(file_data, &tmp_byte);
-		if (retval > 0)
+		if (!retval)
 			retval = put_user(tmp_byte, (__u8 __user *)arg);
 		break;