From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f44.google.com (mail-wm1-f44.google.com [209.85.128.44]) (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 B4074471CE8 for ; Mon, 17 Aug 2026 21:11:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787001101; cv=none; b=RDa+8ty4i3Jvi6j7+RnegrOYmlSK9jnU3RQ3SfMHybwErC1icLm5Fu4UeDgb+0Ih1XjWKlIZ7O5EizBoqjgcjRwAZVVpVYHOFqMs0X0QfRWYIy/bRaZ8EkKkhvNeWjkmofJpzd3NQRa+ASVZ4NEABxbtU/gytDsnZAh+htcQOzg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787001101; c=relaxed/simple; bh=aNLYiY8tiU4jrBfATIo+G+2FSehF6lKWMP6uC1EN+YQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FQ+boy/HEjJA+zS5eItXoQi+Kb884a2OuPmnkVnlzmF90wJZyRFotfk97/cjVIU9DvE2CtXFElA6fSM5ZychvlosUy6OM65IrUj53DqS31HGnoIgcv+E5ECvTPzIx5psRnzJ84J6F6TzvQkW8+SP5d2oN1TJXBscmXhfLryD+oE= 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=ajBla6Ml; arc=none smtp.client-ip=209.85.128.44 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="ajBla6Ml" Received: by mail-wm1-f44.google.com with SMTP id 5b1f17b1804b1-4954f5e8020so20472935e9.2 for ; Mon, 17 Aug 2026 14:11:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1787001098; x=1787605898; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=4Sn4eADzJ/6sfHwf7n+bx/UFgtIfsM24y9dSKsP+YBs=; b=ajBla6MlitU53YnDq7XkgpZcQBFZ6Q3axctz2td5PY3GTwjHHWmxE8b1hS2nkPrBWW /uyIluund1n08nibSwQXztJnQTdg4OSp7WBqIry0wQYQREfiEITrqYVxEgUobhiYx8LV 2A4tnR9MgSfwS0HY+6jIMEopwEPR0+YcOCIYWXtCwE7jNOjLU61gQrIMHKaJDXFc5ncG mdIMJEYk6PtxZKL43e3aspFdUHmaUJQqUa/pBQCZOYhA8dhIy+8Ara+Hgp01vgxrss1E p1evCRrVF5ZsEIfqfWgTaN8gvz3+OJGy4mSMohO8/yfoDM0ZB1jXYDwQCg7uF6n2e4zt RihA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787001098; x=1787605898; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=4Sn4eADzJ/6sfHwf7n+bx/UFgtIfsM24y9dSKsP+YBs=; b=D3W8j09UCjxoMo+aWO0Tal8E7A/Hcl+4zzD6pnnQtGQUhrA2fsdawvAFb58b0tEykl Q+h4bjaypB4fk71hiuIEw0egFA5rC88ESuk5VhCqSUs9jdG6Jz+0aJWNUBq/K3zVdoZd /ZQ3Lm7NZ3DGkT6mgz1pdFO119oWXNx5BBhI0trBS4oCdeFOGj+qTIJS+2Ir1di3Da+b bQ3ATsWYFfKzBl2ukGYF4FKWc4/GrOKY286JENB+vmjlG81zUTu4+ixbYAlEJPPDefXm +FSXZzxsOp/vSR6tFUa5n2eFLMm/BFgWq2GBREPWmxFVCqtv/uJBttIBQok1sda/8mtQ eNZQ== X-Forwarded-Encrypted: i=1; AHgh+RoaiJotnrYlq1zTwgzUNjpWPKUt2AJ5aWt5W7QdxaHjzvKXizVYn/vmiy49XL3Swc4kFUpcj9aSwdcr@vger.kernel.org X-Gm-Message-State: AOJu0Yw9DmqE0tJ2dLC+orBiu7DccOD1qQP52gEUmDIxzrDww9XpN9Gm EbBmTKn1YDyX3EIEpD+RuUBp556v+dbFZ6kZExvn0TN98GnL0qUG2qWh X-Gm-Gg: AR+sD13m+cLImfnSI4RBnBFtq8MwKW0EoM1oY4PNfYw87yvrs+VMMUKZGF+2NyDbkVJ MBQLTDaQ3RxMlhoqp/yu/qxDlFG1QIJlPwY1LzumpVS5755lg1fpV0bByAteniU8qorZEb4doCv yX9VmCCaGcUvLJkGt2rupjvRYOIvca17kbIsXfub+27RVxcJH8F3WE4SutIhdjhp0fajc+Ok3rI AOFTe6mUK1YPXQFwlWZBwEcvQ9nfl1100Q5M28TsUSW9r61FE+RbaPeozRLVYivRP07yafNJVnR 3SRNysAQe0KNaIh/b/n53TNSaS/9EvvL2asZk5D65rDsjo5seWUt9uLvPsQegfCs6XqlhOoxYt0 dxR3WLacQpXSlnAUYZHYnOJlSkgJmo4qu49oSSylDSWp3TdkwT/Vv43Zgy9iWwyBRJWFWFqyx4R Xyq78vzkx/ASTSy3uYf+53FlwgXbL7LX5sKbL/Cx1s9JsaUFYACnvUuwnZwvDJnHFHNJZGJTzel G0wot+Edk86 X-Received: by 2002:a05:600c:4614:b0:499:858f:2653 with SMTP id 5b1f17b1804b1-49987929193mr291105475e9.2.1787001097786; Mon, 17 Aug 2026 14:11:37 -0700 (PDT) Received: from fedora ([105.74.73.207]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49996176b95sm134587625e9.10.2026.08.17.14.11.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Aug 2026 14:11:37 -0700 (PDT) From: Taha Ed-Dafili <0rayn.dev@gmail.com> To: jic23@kernel.org, lars@metafoo.de Cc: Michael.Hennerich@analog.com, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, skhan@linuxfoundation.org, linux@analog.com, linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Taha Ed-Dafili <0rayn.dev@gmail.com> Subject: [PATCH v4 4/6] iio: dac: ad5504: introduce local lock to protect state and spi transfers Date: Mon, 17 Aug 2026 17:11:13 -0400 Message-ID: <20260817211118.21833-5-0rayn.dev@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817211118.21833-1-0rayn.dev@gmail.com> References: <20260817211118.21833-1-0rayn.dev@gmail.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The AD5504 driver currently lacks locking, exposing it to several multi-threading race conditions: 1. The shared DMA-safe SPI transfer buffers (st->data) can be corrupted if multiple threads trigger read_raw or write_raw simultaneously. 2. The ad5504_write_dac_powerdown() routine executes a sequence of back-to-back SPI writes (a CTRL register update followed by a mandatory NOOP). This entire sequence must be atomic. 3. Internal state variables like pwr_down_mask and pwr_down_mode can be read and modified concurrently. Introduce a mutex in the ad5504_state structure and initialize it via devm_mutex_init() in probe. Use the modern scoped guard(mutex) macro at the top-level public IIO callbacks (read_raw, write_raw, and the powerdown attributes) to safely serialize access to the device state and the SPI bus. In ad5504_read_raw() and ad5504_write_raw(), guard(mutex) is scoped to the IIO_CHAN_INFO_RAW case only, since IIO_CHAN_INFO_SCALE merely reads vref_mv, which is fixed at probe time and never modified afterward and therefore needs no serialization. Because guard(mutex) declares a cleanup-scoped variable, it cannot appear directly after a case label; wrap the case body in a compound statement (case IIO_CHAN_INFO_RAW: { ... }) to give it the block scope it requires. Signed-off-by: Taha Ed-Dafili <0rayn.dev@gmail.com> --- Note: The concurrency race conditions addressed in this patch were originally reported by the Sashiko bot: https://sashiko.dev/#/patchset/20260509142047.30302-1-0rayn.dev@gmail.com drivers/iio/dac/ad5504.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/drivers/iio/dac/ad5504.c b/drivers/iio/dac/ad5504.c index 55ce7e49e0e0..87946cdf69e7 100644 --- a/drivers/iio/dac/ad5504.c +++ b/drivers/iio/dac/ad5504.c @@ -7,12 +7,14 @@ #include #include +#include #include #include #include #include #include #include +#include #include #include #include @@ -49,10 +51,12 @@ * @pwr_down_mask: power down mask * @pwr_down_mode: current power down mode * @data: transfer buffer + * @lock: lock to protect state and spi transfers */ struct ad5504_state { struct spi_device *spi; struct regulator *reg; + struct mutex lock; unsigned short vref_mv; unsigned pwr_down_mask; unsigned pwr_down_mode; @@ -103,7 +107,8 @@ static int ad5504_read_raw(struct iio_dev *indio_dev, int ret; switch (m) { - case IIO_CHAN_INFO_RAW: + case IIO_CHAN_INFO_RAW: { + guard(mutex)(&st->lock); ret = ad5504_spi_read(st, chan->address); if (ret < 0) return ret; @@ -111,6 +116,7 @@ static int ad5504_read_raw(struct iio_dev *indio_dev, *val = ret; return IIO_VAL_INT; + } case IIO_CHAN_INFO_SCALE: *val = st->vref_mv; *val2 = chan->scan_type.realbits; @@ -128,11 +134,13 @@ static int ad5504_write_raw(struct iio_dev *indio_dev, struct ad5504_state *st = iio_priv(indio_dev); switch (mask) { - case IIO_CHAN_INFO_RAW: + case IIO_CHAN_INFO_RAW: { + guard(mutex)(&st->lock); if (val >= (1 << chan->scan_type.realbits) || val < 0) return -EINVAL; return ad5504_spi_write(st, chan->address, val); + } default: return -EINVAL; } @@ -148,6 +156,7 @@ static int ad5504_get_powerdown_mode(struct iio_dev *indio_dev, { struct ad5504_state *st = iio_priv(indio_dev); + guard(mutex)(&st->lock); return st->pwr_down_mode; } @@ -156,6 +165,7 @@ static int ad5504_set_powerdown_mode(struct iio_dev *indio_dev, { struct ad5504_state *st = iio_priv(indio_dev); + guard(mutex)(&st->lock); st->pwr_down_mode = mode; return 0; @@ -173,6 +183,7 @@ static ssize_t ad5504_read_dac_powerdown(struct iio_dev *indio_dev, { struct ad5504_state *st = iio_priv(indio_dev); + guard(mutex)(&st->lock); return sysfs_emit(buf, "%d\n", !(st->pwr_down_mask & (1 << chan->channel))); } @@ -185,6 +196,7 @@ static ssize_t ad5504_write_dac_powerdown(struct iio_dev *indio_dev, int ret; struct ad5504_state *st = iio_priv(indio_dev); + guard(mutex)(&st->lock); ret = kstrtobool(buf, &pwr_down); if (ret) return ret; @@ -284,6 +296,10 @@ static int ad5504_probe(struct spi_device *spi) st = iio_priv(indio_dev); + ret = devm_mutex_init(dev, &st->lock); + if (ret) + return ret; + ret = devm_regulator_get_enable_read_voltage(dev, "vcc"); if (ret < 0) return ret; -- 2.55.0