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From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Jonathan Cameron <jic23@kernel.org>
Cc: "Sa, Nuno" <Nuno.Sa@analog.com>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 10/16] iio: adc: max1027: Prevent single channel accesses during buffer reads
Date: Thu, 2 Sep 2021 10:56:19 +0200	[thread overview]
Message-ID: <20210902105619.311e62d9@xps13> (raw)
In-Reply-To: <20210830112024.4583f3cb@jic23-huawei>

Hi Jonathan,

Jonathan Cameron <jic23@kernel.org> wrote on Mon, 30 Aug 2021 11:20:24
+0100:

> On Fri, 20 Aug 2021 07:30:07 +0000
> "Sa, Nuno" <Nuno.Sa@analog.com> wrote:
> 
> > > -----Original Message-----
> > > From: Sa, Nuno <Nuno.Sa@analog.com>
> > > Sent: Friday, August 20, 2021 9:21 AM
> > > To: Miquel Raynal <miquel.raynal@bootlin.com>; Jonathan Cameron
> > > <jic23@kernel.org>; Lars-Peter Clausen <lars@metafoo.de>
> > > Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>; linux-
> > > iio@vger.kernel.org; linux-kernel@vger.kernel.org
> > > Subject: RE: [PATCH 10/16] iio: adc: max1027: Prevent single channel
> > > accesses during buffer reads
> > > 
> > > [External]
> > > 
> > > 
> > >     
> > > > -----Original Message-----
> > > > From: Miquel Raynal <miquel.raynal@bootlin.com>
> > > > Sent: Wednesday, August 18, 2021 1:12 PM
> > > > To: Jonathan Cameron <jic23@kernel.org>; Lars-Peter Clausen
> > > > <lars@metafoo.de>
> > > > Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>; linux-
> > > > iio@vger.kernel.org; linux-kernel@vger.kernel.org; Miquel Raynal
> > > > <miquel.raynal@bootlin.com>
> > > > Subject: [PATCH 10/16] iio: adc: max1027: Prevent single channel
> > > > accesses during buffer reads
> > > >
> > > > [External]
> > > >
> > > > When hardware buffers are enabled (the cnvst pin being the    
> > > trigger),    
> > > > one
> > > > should not mess with the device state by requesting a single channel
> > > > read. Prevent it with a iio_buffer_enabled() check.
> > > >
> > > > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > > > ---
> > > >  drivers/iio/adc/max1027.c | 2 ++
> > > >  1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
> > > > index 223c9e4abd86..83526f3d7d3a 100644
> > > > --- a/drivers/iio/adc/max1027.c
> > > > +++ b/drivers/iio/adc/max1027.c
> > > > @@ -335,6 +335,8 @@ static int max1027_read_raw(struct iio_dev
> > > > *indio_dev,
> > > >
> > > >  	switch (mask) {
> > > >  	case IIO_CHAN_INFO_RAW:
> > > > +		if (iio_buffer_enabled(indio_dev))
> > > > +			return -EBUSY;    
> > > 
> > > I guess 'iio_device_claim_direct_mode()' would be a better option
> > > here? There's nothing preventing this check to pass and then,
> > > concurrently
> > > someone enables the buffer...
> > >     
> > 
> > Taking a second look, it seems that this check is already done [1]? Am I missing
> > I missing something?

You're right, I missed that too.

> > Also, I think we are returning with the 'st->lock' held...
> > 
> > [1]: https://elixir.bootlin.com/linux/latest/source/drivers/iio/adc/max1027.c#L247  
> Absolutely agree this should be done with iio_device_claim_direct_mode() to close the
> possible races.

Didn't know this helper, nice.

> I wonder why this one has been missed in all the cleanups of that stuff? Looks like
> a simple case, but I guess it wasn't immediately visible in the read_raw() function
> so no one noticed.
> 
> Jonathan
> 

Thanks,
Miquèl

  reply	other threads:[~2021-09-02  8:56 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 11:11 [PATCH 00/16] Bring software triggers support to MAX1027-like ADCs Miquel Raynal
2021-08-18 11:11 ` [PATCH 01/16] iio: adc: max1027: Fix wrong shift with 12-bit devices Miquel Raynal
2021-08-20  7:02   ` Sa, Nuno
2021-08-30  9:57     ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 02/16] iio: adc: max1027: Fix the number of max1X31 channels Miquel Raynal
2021-08-20  7:03   ` Sa, Nuno
2021-08-30 10:00     ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 03/16] iio: adc: max1027: Push only the requested samples Miquel Raynal
2021-08-20  7:10   ` Sa, Nuno
2021-08-30 10:07     ` Jonathan Cameron
2021-08-30 10:49       ` Sa, Nuno
2021-08-30 14:29         ` Jonathan Cameron
2021-08-30 15:02           ` Sa, Nuno
2021-09-01  8:12             ` Miquel Raynal
2021-09-04 14:06               ` Jonathan Cameron
2021-09-06  8:59               ` Sa, Nuno
2021-09-06 16:56                 ` Jonathan Cameron
2021-09-06 17:34                   ` Miquel Raynal
2021-08-30 10:06   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 04/16] iio: adc: max1027: Lower conversion time Miquel Raynal
2021-08-20  7:12   ` Sa, Nuno
2021-08-30 10:10   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 05/16] iio: adc: max1027: Drop extra warning message Miquel Raynal
2021-08-20  7:12   ` Sa, Nuno
2021-08-30 10:12   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 06/16] iio: adc: max1027: Rename a helper Miquel Raynal
2021-08-20  7:13   ` Sa, Nuno
2021-08-18 11:11 ` [PATCH 07/16] iio: adc: max1027: Create a helper to configure the trigger Miquel Raynal
2021-08-20  7:16   ` Sa, Nuno
2021-08-30 10:16   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 08/16] iio: adc: max1027: Explain better how the trigger state gets changed Miquel Raynal
2021-08-20  7:17   ` Sa, Nuno
2021-08-18 11:11 ` [PATCH 09/16] iio: adc: max1027: Create a helper to configure the channels to scan Miquel Raynal
2021-08-20  7:18   ` Sa, Nuno
2021-08-18 11:11 ` [PATCH 10/16] iio: adc: max1027: Prevent single channel accesses during buffer reads Miquel Raynal
2021-08-20  7:20   ` Sa, Nuno
2021-08-20  7:30     ` Sa, Nuno
2021-08-30 10:20       ` Jonathan Cameron
2021-09-02  8:56         ` Miquel Raynal [this message]
2021-08-18 11:11 ` [PATCH 11/16] iio: adc: max1027: Separate the IRQ handler from the read logic Miquel Raynal
2021-08-20  7:23   ` Sa, Nuno
2021-09-02  8:55     ` Miquel Raynal
2021-09-04 14:08       ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 12/16] iio: adc: max1027: Introduce an end of conversion helper Miquel Raynal
2021-08-20  7:28   ` Sa, Nuno
2021-09-02  9:26     ` Miquel Raynal
2021-08-30 10:34   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 13/16] iio: adc: max1027: Prepare re-using the EOC interrupt Miquel Raynal
2021-08-20  7:31   ` Sa, Nuno
2021-08-30 10:30   ` Jonathan Cameron
2021-08-30 10:47   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 14/16] iio: adc: max1027: Consolidate the end of conversion helper Miquel Raynal
2021-08-20  7:45   ` Sa, Nuno
2021-08-30 10:37   ` Jonathan Cameron
2021-08-30 12:44     ` Sa, Nuno
2021-08-30 14:32       ` Jonathan Cameron
2021-09-02 15:12       ` Miquel Raynal
2021-09-03 14:28         ` Sa, Nuno
2021-09-03 14:46           ` Miquel Raynal
2021-09-05  9:41             ` Jonathan Cameron
2021-09-06  9:12               ` Sa, Nuno
2021-09-06  9:30                 ` Sa, Nuno
2021-08-18 11:11 ` [PATCH 15/16] iio: adc: max1027: Support software triggers Miquel Raynal
2021-08-20  7:58   ` Sa, Nuno
2021-09-02 12:25     ` Miquel Raynal
2021-09-03 14:20       ` Sa, Nuno
2021-08-30 10:50   ` Jonathan Cameron
2021-09-02 15:21     ` Miquel Raynal
2021-09-05  9:43       ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 16/16] iio: adc: max1027: Enable software triggers to be used without IRQ Miquel Raynal
2021-08-30 10:54   ` Jonathan Cameron

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