From nobody Mon Jun 8 05:24:53 2026 Received: from mail-pg1-f182.google.com (mail-pg1-f182.google.com [209.85.215.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 848F4364EA5 for ; Mon, 1 Jun 2026 19:09:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.182 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780340980; cv=none; b=Nu9oXBSEK3FB86Vw4BnqiHJgGULUsVAZkbugrKbFRj5ggUYlrVw+Sb1EEGnavrSnnxcQoxRbWeYoLeXFct23wqGGlnLRl4mJ+gLP79rV2MLbkob55uHpF8fVRY+ObnXmtugxmhhSAirGxKzidRNo7mv7bFEc38gNNFtnpax1FZA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780340980; c=relaxed/simple; bh=NzFHien8AQ3W2uRrt9KsIcrUygBSpklL/qEaq/faO9A=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=cUuwZ+HZeYQ7bagDqaA3ayLhLcxlv5XZO9aBHbdp9UDNSudZwEPOQga18EP0XKV2Yt1CV8TDKPYU3bxorqpf1goCuwTxdsYQEJiOCiU3dx5RpvF67t528ECkBnxQb2LyZih/6las8jwE/lsfEKC3pQWFGsbgT6eW+Vw3QHrjkfY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=OLs7VogZ; arc=none smtp.client-ip=209.85.215.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="OLs7VogZ" Received: by mail-pg1-f182.google.com with SMTP id 41be03b00d2f7-c857d04cc99so1076391a12.0 for ; Mon, 01 Jun 2026 12:09:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1780340979; x=1780945779; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=aJOXn1og4jyTJwWf53fIN3cU7RwZav+WgVRJvKPTYOg=; b=OLs7VogZ5CdpaWRccKyJZu7pIun/aUh7vTOR9HhGbVR77Tt66D5Oje1+MD5tZ5xLAn DkYDm6BqltQeor3Ly8K1k7tMylR+VgdLdARmZhUoK/9bvI5XJyL00/nTCPiSQg/cMrbd dHEaB5mVWXJ8cIGgDmOY1Tb8gjpsHF90dqYiLO8HPl4mue9wvGw4jtTUyLnoDxunQwck qXxhYi1qYHSDznqmjVAIi5LCBe0IAGh1tAMtBGTWMUugEijZggL1UlP6UFDQ/nnqdHsn xRuwpxZW7IpsV2uKwKOIyIe+7TjE0vxoWoi9l0CD7X56SpuK5C0b73CCxTaEeoWaFMP8 9H7w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780340979; x=1780945779; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=aJOXn1og4jyTJwWf53fIN3cU7RwZav+WgVRJvKPTYOg=; b=WQ3SJ7pfZPKRMBlEkd920f21PoT/DYxV+YGoru9rI8f0F/yNudvb/Uv4Ze/6TfurzK EVzYkNzos0I5VzGbvJfx0LYkREQY6p5JXsJ1qLi23493LUys/TR7ARxgiBpGAFNcrzFM EOaBXxE93ewrAS1ZTx3R2KdkQxftxKpA9eOj6fEgCCmhhFGdt7DUQXtLLtrSsdyMNIZK amU88eyw8PTn9zrr9qnZX0+TKDXaPGY/+EhbeBXyqluGi7/GrLxX31cc/PjzlANn8UxS zTgESedp5F5I+DxvUZn6AMRuHaXAX7TeJt6orkQa9B4Nq7OYSi8wKiFm09cij7t7WJoC hpow== X-Forwarded-Encrypted: i=1; AFNElJ9H8dbgLcfcZugmlHtWl50jJWbNtgssYb9FRtkegmOsmzO68r2Ll7rO05m2PDMKtqCpqELjFeotleyR8jM=@vger.kernel.org X-Gm-Message-State: AOJu0YwtacL4gvM1wvoWmYTlFUH9LMF9iwvLY7PpV2+/etc3tSZoeol+ CEKUae3z0R/Bmc6OA1QEMvrlPa13ResngthPAGqa1kCclxnZmjDGzEpZzDRuFQ== X-Gm-Gg: Acq92OGHcXzz1QTuY8dBAznz0Bi6t4dpWgvmHKAD437+YYjOQBoUjnnabGceuybY3f2 faWjWAhJeJdFNf0YyPDrbUdU9iQHTkbFuVt46BtRK5pDFTghepY7WjUByiZPrLfa9NKFH85kLiu hew6oJguY7ceuHyevoO42h1FRc5huPCQJ/HLP3iRVbluWr4Nnn/P1yJ/9H9soukBwmPL/X8DJJP pYFUhnTXMDMPHnYQRAOrAC8fHBwSujtm/h9FS5OJcaBObn+5TYJZqYFFJJGJcwEzRfZ9JanFT9i ORcgne8aMMJKk0LumnH7fxz5o+hJXQchtMXQtYvEoVsc8KTiHa01KvlfACVtjedelZNmx8s68Q2 1jcCDXpiE8de1Ds+cEOz2nAJMGdxu51p2GeJLXynrLkWBE+3ZHWBVNpjAgtBuMNdIvA/LCNVwpr 1KcCIDMYnMHAv+kAPHIr91JjL8JEUrL2JF3JVxam5dO+MzBFv0JQ5rlOXXYHT7GKIszYcwCZPDa 4QZCo8FvFR+xftq9+jG7G9nun924shO8zFPv944HKgmdg== X-Received: by 2002:a05:6a20:3c89:b0:3b3:e4d:5071 with SMTP id adf61e73a8af0-3b4785b0abfmr738872637.0.1780340978672; Mon, 01 Jun 2026 12:09:38 -0700 (PDT) Received: from ryzen ([2601:644:8000:5b5d:7285:c2ff:fe45:8a32]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c85772d7342sm10593813a12.26.2026.06.01.12.09.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Jun 2026 12:09:38 -0700 (PDT) From: Rosen Penev To: linux-ide@vger.kernel.org Cc: Damien Le Moal , Niklas Cassel , linux-kernel@vger.kernel.org (open list) Subject: [PATCH] ata: pata_ep93xx: fix endianness bug in trailing byte transfer Date: Mon, 1 Jun 2026 12:09:21 -0700 Message-ID: <20260601190921.20167-1-rosenp@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" ep93xx_pata_data_xfer() handles a trailing odd byte by reading/writing a full 16-bit word and extracting the first byte. The current code uses cpu_to_le16()/le16_to_cpu() wrapping, but then assigns through a u8 pointer (*pad), truncating the value. On the READ path, *pad =3D cpu_to_le16(...) truncates the u16 to u8. On little-endian this happens to give the right byte, but on big-endian cpu_to_le16() puts the valid byte in the upper 8 bits and truncation keeps the lower 8 bits (zeros), losing the data. On the WRITE path, le16_to_cpu(*pad) zero-extends pad[0] (u8) to u16 (0x00BB) and then on big-endian byte-swaps to 0xBB00. The hardware then receives 0x00 as the first byte instead of 0xBB. The readl()/writel() calls inside ep93xx_pata_read_data() and ep93xx_pata_write_data() already handle endianness correctly, so the trailing byte can just use the raw read/write value directly without the cpu_to_le16/le16_to_cpu wrappers. Remove the pad[] array and simplify. Assisted-by: Opencode:Big-Pickle Signed-off-by: Rosen Penev --- drivers/ata/pata_ep93xx.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff --git a/drivers/ata/pata_ep93xx.c b/drivers/ata/pata_ep93xx.c index 3f61712af5bb..a0dfdacf54e5 100644 --- a/drivers/ata/pata_ep93xx.c +++ b/drivers/ata/pata_ep93xx.c @@ -495,19 +495,12 @@ static unsigned int ep93xx_pata_data_xfer(struct ata_= queued_cmd *qc, =20 /* Transfer trailing 1 byte, if any. */ if (unlikely(buflen & 0x01)) { - unsigned char pad[2] =3D { }; - buf +=3D buflen - 1; =20 if (rw =3D=3D READ) { - *pad =3D cpu_to_le16( - ep93xx_pata_read_data( - drv_data, IDECTRL_ADDR_DATA)); - *buf =3D pad[0]; + *buf =3D ep93xx_pata_read_data(drv_data, IDECTRL_ADDR_DATA); } else { - pad[0] =3D *buf; - ep93xx_pata_write_data(drv_data, le16_to_cpu(*pad), - IDECTRL_ADDR_DATA); + ep93xx_pata_write_data(drv_data, *buf, IDECTRL_ADDR_DATA); } words++; } --=20 2.54.0