linux-kernel - Re: [PATCH] iio: adc: ti-ads7950: add GPIO support

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Message-ID: <2e692086-4be5-10ea-34b0-4444995c4275@lechnology.com>
Date:   Sat, 9 Feb 2019 12:56:11 -0600
From:   David Lechner <david@...hnology.com>
To:     Jonathan Cameron <jic23@...nel.org>, justinpopo6@...il.com
Cc:     linux-iio@...r.kernel.org, linux-gpio@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com, f.fainelli@...il.com,
        bgolaszewski@...libre.com, linus.walleij@...aro.org,
        knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: adc: ti-ads7950: add GPIO support

On 2/9/19 11:00 AM, Jonathan Cameron wrote:
> Nope.  This is a state lock used to protect against transitions between
> different modes of the IIO device (buffered vs polled), it
> isn't suitable for general use.
> 
> The driver should be modified to handle that correctly.
> We have iio_claim_direct_mode etc that deal with the case
> where a device can't do certain operations whilst in buffered
> mode.  Note it can fail and should.
> 
> Seems there are more drivers still doing this than I thought.
> If anyone is bored and wants to clean them out, that would be
> most appreciated!
> 
> If you need locking to protect a local buffer or the device
> state, define a new lock to do it with clearly documented
> scope.

Just as a reminder, there is a use case for this particular
chip that requires buffered mode and direct mode at the same
time.

https://patchwork.kernel.org/patch/10539021/
https://patchwork.kernel.org/patch/10527757/