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

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Date:   Sat, 28 Jan 2023 15:34:57 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Doug Anderson <dianders@...omium.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        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>,
        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, 25 Jan 2023 19:39:46 +0000
Matthias Kaehlcke <mka@...omium.org> wrote:

> On Mon, Jan 23, 2023 at 03:12:06PM -0800, Doug Anderson wrote:
> > Hi,
> > 
> > On Mon, Jan 23, 2023 at 8:35 AM Konrad Dybcio <konrad.dybcio@...aro.org> wrote:  
> > >
> > > On 22.01.2023 18:24, Jonathan Cameron wrote:  
> > > > 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.  
> > > + Doug
> > >
> > > Unless the Chromium folks relied on the old names (they're the
> > > only ones I can think of that actually could have tapped into
> > > this), I say green light!  
> > 
> > Thanks for the CC. I _think_ the only place we use these ADCs is for
> > certain thermistors and I think that those are all just hooked up in
> > the device tree, so the channel name doesn't matter. I'll also note
> > that no Qualcomm Chromebooks are shipping with anything newer than
> > kernel 5.15 right now, and (I checked) the ChromeOS 5.15 tree doesn't
> > have commit 4f47a236a23d ("iio: adc: qcom-spmi-adc5: convert to device
> > properties"). Thus, even if I'm wrong and the name is used someplace
> > hidden then the "old" name would be better for us. I haven't tested
> > the patch myself, but it sounds as if ${SUBJECT} patch is actually
> > moving us back to the old name.
> > 
> > +Matthias to keep me honest since he's spent more time with the ADCs.  
> 
> Agreed that the channel name doesn't matter, Chrome OS currently only
> uses the ADCs for thermal zones controlled by the kernel.

Great.  Thanks for all the info. 

Applied to the fixes-togreg branch of iio.git and marked for stable.

Jonathan

> 
> > > > 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);  
> > > >