Message-ID: <5544B358.1060208@kernel.org>
Date: Sat, 02 May 2015 12:22:00 +0100
From: Jonathan Cameron <jic23@kernel.org>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0
MIME-Version: 1.0
To: Gabriele Mazzotta <gabriele.mzt@gmail.com>
CC: knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net,
        marxin.liska@gmail.com, marex@denx.de, rui.zhang@intel.com,
        linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org
Subject: Re: [PATCH] iio: acpi: Add ACPI0008 Ambient Light Sensor
References: <1430306845-7117-1-git-send-email-gabriele.mzt@gmail.com> <10033848.82LkUmdQLq@xps13>
In-Reply-To: <10033848.82LkUmdQLq@xps13>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1548
Lines: 47

On 01/05/15 17:12, Gabriele Mazzotta wrote:
> Hi,
> 
> probably this is not completely related to this driver, but I
> noticed something while testing it.
> 
> When I load acpi-als, /sys/bus/iio/devices/iio:device0/buffer/enable
> is 0. If I try to set it to 1, I get the following error:
> "Buffer not started: buffer parameter update failed (-22)"
> 
> After I got the error, I can successfully toggle "enable".
> 
> What I found is that the first time iio_request_update_kfifo() is
> called, __iio_allocate_kfifo() gets called. Since bytes_per_datum
> is 0 (as set iio_compute_scan_bytes()), it returns -EINVAL and so
> does iio_request_update_kfifo(), causing the error above.
> 
> Subsequent calls of iio_request_update_kfifo() will return 0 as
> update_needed is false, so "enable" can be toggled with no errors.
> 
> Isn't there something wrong here?
Definitely looks like it!

Thanks for pointing this out.  Anyhow, the issue is exactly what you've
identified; the line below the __iio_allocate_kfifo clears the
update needed whether or not it succeeded.  Clearly it should not
be doing that if a failure has occurred.

Would you mind submitting a fix patch for this?
Simply checking ret before setting updateneeded to false
should do the job.

Thanks,

Jonathan

 
> 
> Regards,
> Gabriele
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/