linux-kernel - Re: [PATCH v2 1/1] iio: adc: qcom-spmi-adc5: Fix the channel name

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Date:   Sun, 22 Jan 2023 17:24:41 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Nuno Sá <nuno.sa@...log.com>,
        linux-arm-msm@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: Re: [PATCH v2 1/1] iio: adc: qcom-spmi-adc5: Fix the channel name

On Wed, 18 Jan 2023 12:06:23 +0200
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> The node name can contain an address part which is unused
> by the driver. Moreover, this string is propagated into
> the userspace label, sysfs filenames *and breaking ABI*.
> 
> Cut the address part out before assigning the channel name.
> 
> Fixes: 4f47a236a23d ("iio: adc: qcom-spmi-adc5: convert to device properties")
> Reported-by: Marijn Suijten <marijn.suijten@...ainline.org>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

LGTM, but given it will have ABI impact, I'd like to hear from 
Andy, Bjorn or Konrad as maintainers and /or Dmitry as someone
who has touched this driver fairly recently.

Mostly I want to be sure they know this exists before it causes surprise.

Jonathan

> ---
> v2: rephrased commit message (Marijn), fixed compilation issue (Marijin)
>  drivers/iio/adc/qcom-spmi-adc5.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/adc/qcom-spmi-adc5.c b/drivers/iio/adc/qcom-spmi-adc5.c
> index e90c299c913a..c2d5e06f137a 100644
> --- a/drivers/iio/adc/qcom-spmi-adc5.c
> +++ b/drivers/iio/adc/qcom-spmi-adc5.c
> @@ -628,12 +628,20 @@ static int adc5_get_fw_channel_data(struct adc5_chip *adc,
>  				    struct fwnode_handle *fwnode,
>  				    const struct adc5_data *data)
>  {
> -	const char *name = fwnode_get_name(fwnode), *channel_name;
> +	const char *channel_name;
> +	char *name;
>  	u32 chan, value, varr[2];
>  	u32 sid = 0;
>  	int ret;
>  	struct device *dev = adc->dev;
>  
> +	name = devm_kasprintf(dev, GFP_KERNEL, "%pfwP", fwnode);
> +	if (!name)
> +		return -ENOMEM;
> +
> +	/* Cut the address part */
> +	name[strchrnul(name, '@') - name] = '\0';
> +
>  	ret = fwnode_property_read_u32(fwnode, "reg", &chan);
>  	if (ret) {
>  		dev_err(dev, "invalid channel number %s\n", name);