From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B3CA22765ED; Wed, 10 Dec 2025 06:35:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765348508; cv=none; b=UcdvsCzut1TXNJfCo9iEjokYPeB3nDcZq/rLRrlluD5Y4j3Xu5i0TpuO/+bDa0pgIUJvM2FWErS7Kv0jijD/VZR0Q2m9FnlMmtKfXmMh7gpbGERzIqqKZekjWV7px+bVs2aGJdQ/if9Vy/0j1SnsY3GfrLlfx7EyogE/0FzhkJ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765348508; c=relaxed/simple; bh=2abPAY+96Y1qNcmycm/yEHvcX3RLzB0mV1G58gCEx1o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=T2JlvqKZTvjMvcDvNbxtz0e3Yv33/LfYncxXoreUIcjRHGYGF/G3dxXLCOsrCQa5uhgWZ5U7lUx0X2I0fFaWB7XephDUIp1YqT7BZvogh/xCYx0/MEFXQRXNfYOTf21jQ5OQvLMTu3XnW9x6EAPD2WAS+veEa11tQRJ9oA9tdxw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MQLJ3ytI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MQLJ3ytI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E387FC4CEF1; Wed, 10 Dec 2025 06:35:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765348505; bh=2abPAY+96Y1qNcmycm/yEHvcX3RLzB0mV1G58gCEx1o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MQLJ3ytIRVomsTQnMpfVWoZpUmR34enoP3tOgAyK5cG2rFwh8yb5FBtj5SJYWy/1w I8Tx1Ak1kd+8QHd1BaedtAC2FnBqBtJmyfII9MgTLVW8I/OD3Tk+SqAkD0fderATxZ MoRDOfL5i+C8sqvnZbAQ4lax9Yw6ZyCwfWhFGbFMN/gs8B+G1wM7ASjC2yPzN/LeJG WYrXWKenHCp36vVuiTggA0Ucj6+0C4fiUAFn2XlJNuUZkv50lI2MsRAmL2qwZ7G6ig PCUKN6dX4/L8qvWDagz89uWlSspiEdxPg8r2KYAtRQGwpkoNLAskZ7lwpamIo9MO7w gaLBFVri23QSw== From: Sasha Levin To: patches@lists.linux.dev, stable@vger.kernel.org Cc: Pei Xiao , kernel test robot , Jonathan Cameron , Sasha Levin , dixitparmar19@gmail.com Subject: [PATCH AUTOSEL 6.18-6.1] iio: adc: ti_am335x_adc: Limit step_avg to valid range for gcc complains Date: Wed, 10 Dec 2025 01:34:33 -0500 Message-ID: <20251210063446.2513466-4-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251210063446.2513466-1-sashal@kernel.org> References: <20251210063446.2513466-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.18 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Pei Xiao [ Upstream commit c9fb952360d0c78bbe98239bd6b702f05c2dbb31 ] FIELD_PREP() checks that a value fits into the available bitfield, add a check for step_avg to fix gcc complains. which gcc complains about: drivers/iio/adc/ti_am335x_adc.c: In function 'tiadc_step_config': include/linux/compiler_types.h:572:38: error: call to '__compiletime_assert_491' declared with attribute error: FIELD_PREP: value too large for the field include/linux/mfd/ti_am335x_tscadc.h:58:29: note: in expansion of macro 'FIELD_PREP' #define STEPCONFIG_AVG(val) FIELD_PREP(GENMASK(4, 2), (val)) ^~~~~~~~~~ drivers/iio/adc/ti_am335x_adc.c:127:17: note: in expansion of macro 'STEPCONFIG_AVG' stepconfig = STEPCONFIG_AVG(ffs(adc_dev->step_avg[i]) - 1) Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202510102117.Jqxrw1vF-lkp@intel.com/ Signed-off-by: Pei Xiao Signed-off-by: Jonathan Cameron Signed-off-by: Sasha Levin --- LLM Generated explanations, may be completely bogus: Now I understand the full context: **Key findings:** - `STEPCONFIG_AVG(val)` uses `FIELD_PREP(GENMASK(4, 2), (val))` - a 3-bit field - `STEPCONFIG_AVG_16` = `STEPCONFIG_AVG(4)` = 16 (the register value) - `step_avg[i]` stores the number of samples (1, 2, 4, 8, 16) - The comparison `step_avg[i] <= STEPCONFIG_AVG_16` bounds step_avg to ≤ 16 ### SUMMARY | Criterion | Assessment | |-----------|------------| | **Type of fix** | BUILD FIX - compile error | | **Size** | 1 line change | | **Risk** | Very Low | | **User impact** | Prevents kernel compilation failure | | **Subsystem** | TI AM335x ADC (BeagleBone, embedded systems) | | **Cc: stable** | No | | **Fixes: tag** | No | | **Reported-by** | Yes (kernel test robot) | ### ASSESSMENT **Why this should be backported:** 1. **Build Fix Category**: This explicitly fixes a GCC compilation error. Build fixes are one of the allowed exception categories for stable trees because they prevent users from being able to compile the kernel at all. 2. **The Error is a Hard Failure**: The gcc error `error: call to '__compiletime_assert_491' declared with attribute error: FIELD_PREP: value too large for the field` is a hard compilation failure, not just a warning. Users with certain GCC versions/configurations cannot build the kernel with this driver enabled. 3. **Minimal Risk**: The fix simply adds a bounds check (`&& adc_dev->step_avg[i] <= STEPCONFIG_AVG_16`) to an existing condition. Invalid values now fall through to the else branch (default behavior), which is safe. 4. **No Functional Change for Valid Inputs**: For valid step_avg values (1, 2, 4, 8, 16), the behavior is identical. Only theoretically invalid values are now handled differently. 5. **Driver Exists in All Stable Trees**: The TI AM335x ADC driver has been in the kernel for years and exists in all active stable branches. **Concerns:** - No explicit `Cc: stable` tag - No `Fixes:` tag - The maintainer didn't specifically request backporting However, the absence of these tags doesn't disqualify a build fix. Build fixes are essential for kernel buildability and are routinely backported. The fix is obviously correct, small, contained, and addresses a real build failure reported by the kernel test robot infrastructure. It meets the stable kernel criteria for a build fix. **YES** drivers/iio/adc/ti_am335x_adc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c index 99f274adc870d..a1a28584de930 100644 --- a/drivers/iio/adc/ti_am335x_adc.c +++ b/drivers/iio/adc/ti_am335x_adc.c @@ -123,7 +123,7 @@ static void tiadc_step_config(struct iio_dev *indio_dev) chan = adc_dev->channel_line[i]; - if (adc_dev->step_avg[i]) + if (adc_dev->step_avg[i] && adc_dev->step_avg[i] <= STEPCONFIG_AVG_16) stepconfig = STEPCONFIG_AVG(ffs(adc_dev->step_avg[i]) - 1) | STEPCONFIG_FIFO1; else -- 2.51.0