FAILED: patch "[PATCH] ASoC: renesas: rz-ssi: Add a check for negative sample_space" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 82a0a3e6f8c02b3236b55e784a083fa4ee07c321
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025021054-entangled-amuser-e6ea@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 82a0a3e6f8c02b3236b55e784a083fa4ee07c321 Mon Sep 17 00:00:00 2001
From: Dan Carpenter <[email protected]>
Date: Wed, 8 Jan 2025 12:28:46 +0300
Subject: [PATCH] ASoC: renesas: rz-ssi: Add a check for negative sample_space

My static checker rule complains about this code. The concern is that if "sample_space" is negative then the "sample_space >= runtime->channels" condition will not work as intended because it will be type promoted to a high unsigned int value.

strm->fifo_sample_size is SSI_FIFO_DEPTH (32). The SSIFSR_TDC_MASK is 0x3f. Without any further context it does seem like a reasonable warning and it can't hurt to add a check for negatives.

index d48e2e7356b6..3a0af4ca7ab6 100644
@@ -521,6 +521,8 @@ static int rz_ssi_pio_send(struct rz_ssi_priv *ssi, struct rz_ssi_stream *strm)
 	sample_space = strm->fifo_sample_size;
 	ssifsr = rz_ssi_reg_readl(ssi, SSIFSR);
 	sample_space -= (ssifsr >> SSIFSR_TDC_SHIFT) & SSIFSR_TDC_MASK;
+	if (sample_space < 0)
+		return -EINVAL;
 
 	/* Only add full frames at a time */
 	while (frames_left && (sample_space >= runtime->channels)) {