From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-177.mta0.migadu.com (out-177.mta0.migadu.com [91.218.175.177]) (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 2D57C745E0 for ; Thu, 14 Mar 2024 17:30:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710437419; cv=none; b=m91JFnsPb3JwGnHnxfGTw0DJ54wC/lMS8SuWnWrwA4WPZjNAaY4QMng7pNcJDjOnKORFfTYo474oQNNec9xsEiSNQ53hagSZIJghGkBj1KFMqhlZKngfz/rXhNcAUs2jPQIGFh61mD5ZBuABWGASEIGAA8nCSpzYVluvXdowMMs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710437419; c=relaxed/simple; bh=mvbufNwV6uuDAXa1Za1BY8YcXWB+UiVwFDzPNSHkqwg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=J9Ngj3Ka+XcKMbzK6fqXL3W5wvCXu/UpGtwRBHaPBBpzq5grRBs+m2EGY8LwVPe+rxOdg68OMubr+s1z6uYZmvVPokbKxDFmvrP6rONLbaRhsBFrBF1YVMD+a3sh3x6iIQM/F5QTn3F2n5gWwwQ907PYqyo9BgtJHTIZS5RPrSY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=VnhCHumO; arc=none smtp.client-ip=91.218.175.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="VnhCHumO" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1710437415; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JEBIKds7ABWFBzR1V0Wt+1agR4evvGmxh9zbarQta3w=; b=VnhCHumOkxcleb39VeThgoudLqqD/mLpqBVDSxM7QxzkuClZzRHq7SMzyrTSMLIitFAQqa eofiaPewK/4Z3tmEtoiz49+xrtpK5vINFQ2y5oanaW0uQgI45+yiPeqxQk/nxO93d95i2l TtXVPnZt2RVGUdfC51fYAD+ERj7kAPQ= Date: Thu, 14 Mar 2024 13:30:11 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] iio: xilinx-ams: Don't include ams_ctrl_channels in scan_mask Content-Language: en-US To: Jonathan Cameron Cc: linux-iio@vger.kernel.org, Conall O'Griofa , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Lars-Peter Clausen References: <20240311162800.11074-1-sean.anderson@linux.dev> <20240314154824.37150a54@jic23-huawei> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Sean Anderson In-Reply-To: <20240314154824.37150a54@jic23-huawei> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 3/14/24 11:48, Jonathan Cameron wrote: > On Mon, 11 Mar 2024 12:28:00 -0400 > Sean Anderson wrote: > >> ams_enable_channel_sequence constructs a "scan_mask" for all the PS and >> PL channels. This works out fine, since scan_index for these channels is >> less than 64. However, it also includes the ams_ctrl_channels, where >> scan_index is greater than 64, triggering undefined behavior. Since we >> don't need these channels anyway, just exclude them. >> >> Fixes: d5c70627a794 ("iio: adc: Add Xilinx AMS driver") >> Signed-off-by: Sean Anderson > > Hi Sean, > > I'd ideally like to understand why we have channels with such large > scan indexes. Those values should only be used for buffered capture. > It feels like they are being abused here. Can we set them to -1 instead > and check based on that? > For a channel, a scan index of -1 means it can't be captured via the buffered > interfaces but only accessed via sysfs reads. > I think that's what we have here? >From what I can tell, none of the channels support buffered reads. And we can't naïvely convert the scan_index to -1, since that causes sysfs naming conflicts (not to mention the compatibility break). > > I just feel like if we leave these as things stand, we will get bitten > by similar bugs in the future. At least with -1 it should be obvious why! There are just as likely to be bugs confusing the PL/PS subdevices... FWIW I had no trouble identifying the channels involved with this bug. --Sean > Jonathan > > >> --- >> >> drivers/iio/adc/xilinx-ams.c | 8 ++++++-- >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/iio/adc/xilinx-ams.c b/drivers/iio/adc/xilinx-ams.c >> index a55396c1f8b2..4de7ce598e4d 100644 >> --- a/drivers/iio/adc/xilinx-ams.c >> +++ b/drivers/iio/adc/xilinx-ams.c >> @@ -414,8 +414,12 @@ static void ams_enable_channel_sequence(struct iio_dev *indio_dev) >> >> /* Run calibration of PS & PL as part of the sequence */ >> scan_mask = BIT(0) | BIT(AMS_PS_SEQ_MAX); >> - for (i = 0; i < indio_dev->num_channels; i++) >> - scan_mask |= BIT_ULL(indio_dev->channels[i].scan_index); >> + for (i = 0; i < indio_dev->num_channels; i++) { >> + const struct iio_chan_spec *chan = &indio_dev->channels[i]; >> + >> + if (chan->scan_index < AMS_CTRL_SEQ_BASE) >> + scan_mask |= BIT_ULL(chan->scan_index); >> + } >> >> if (ams->ps_base) { >> /* put sysmon in a soft reset to change the sequence */ >