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([2401:4900:93a0:18ce:f596:eb56:eb0e:e913]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ae83e57740sm76390325ad.15.2026.03.08.05.47.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 08 Mar 2026 05:47:22 -0700 (PDT) From: Tabrez Ahmed To: Guenter Roeck Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, Shuah Khan , Brigham Campbell , Tabrez Ahmed Subject: [PATCH] hwmon: (ads7871) Propagate SPI errors in voltage_show Date: Sun, 8 Mar 2026 18:17:14 +0530 Message-ID: <20260308124714.84715-1-tabreztalks@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-hwmon@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The voltage_show() function previously ignored negative error codes returned by the underlying SPI read/write functions. Because negative numbers have their most significant bits set in two's complement, a failed SPI read returning -EIO (-5) would incorrectly evaluate to true when masked with MUX_CNV_BM (0x80). This would cause the driver to enter the polling loop even when the SPI bus failed, eventually returning a misleading -ETIMEDOUT error to userspace instead of the actual hardware error. Furthermore, the return values of the initial SPI write and the final 16-bit SPI read were completely ignored. Add proper error checking after every SPI operation to ensure hardware failures are immediately propagated back to userspace. Suggested-by: Guenter Roeck Signed-off-by: Tabrez Ahmed --- drivers/hwmon/ads7871.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c index 753bf77ce19b4..9bfdf9e6bcd77 100644 --- a/drivers/hwmon/ads7871.c +++ b/drivers/hwmon/ads7871.c @@ -104,10 +104,14 @@ static ssize_t voltage_show(struct device *dev, struct device_attribute *da, */ /*MUX_M3_BM forces single ended*/ /*This is also where the gain of the PGA would be set*/ - ads7871_write_reg8(spi, REG_GAIN_MUX, - (MUX_CNV_BM | MUX_M3_BM | channel)); + ret = ads7871_write_reg8(spi, REG_GAIN_MUX, + (MUX_CNV_BM | MUX_M3_BM | channel)); + if (ret < 0) + return ret; ret = ads7871_read_reg8(spi, REG_GAIN_MUX); + if (ret < 0) + return ret; mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV); /* * on 400MHz arm9 platform the conversion @@ -116,12 +120,16 @@ static ssize_t voltage_show(struct device *dev, struct device_attribute *da, while ((i < 2) && mux_cnv) { i++; ret = ads7871_read_reg8(spi, REG_GAIN_MUX); + if (ret < 0) + return ret; mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV); msleep_interruptible(1); } if (mux_cnv == 0) { val = ads7871_read_reg16(spi, REG_LS_BYTE); + if (val < 0) + return val; /*result in volts*10000 = (val/8192)*2.5*10000*/ val = ((val >> 2) * 25000) / 8192; return sysfs_emit(buf, "%d\n", val); -- 2.43.0