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Message-ID: <CA+U=Dspk0G+b-M3k1m7SCCPfAoFxksqzHxCSs8BWnsrSr_afOw@mail.gmail.com>
Date: Wed, 21 Jul 2021 10:23:45 +0300
From: Alexandru Ardelean <ardeleanalex@...il.com>
To: Théo Borém Fabris <theobf@....br>
Cc: Jonathan Cameron <jic23@...nel.org>,
Lars-Peter Clausen <lars@...afoo.de>,
linux-iio <linux-iio@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: dac: max5821: convert device register to device
managed function
On Wed, Jul 21, 2021 at 3:11 AM Théo Borém Fabris <theobf@....br> wrote:
>
> Em ter., 20 de jul. de 2021 às 04:22, Alexandru Ardelean
> <ardeleanalex@...il.com> escreveu:
> >
> > On Mon, Jul 19, 2021 at 6:25 PM Théo Borém Fabris <theobf@....br> wrote:
> > >
> > > Hi, Alexandru.
> > >
> > > Em seg., 19 de jul. de 2021 às 04:33, Alexandru Ardelean
> > > <ardeleanalex@...il.com> escreveu:
> > > >
> > > > On Sun, Jul 18, 2021 at 11:42 PM Théo Borém Fabris <theobf@....br> wrote:
> > > > >
> > > > > Add a device managed hook, via devm_add_action_or_reset() and
> > > > > max5821_regulator_disable(), to disable voltage regulator on device
> > > > > detach.
> > > > > Replace iio_device_register() by devm_iio_device_register() and remove
> > > > > the max5821_remove() function used to unregister the device and disable the
> > > > > voltage regulator.
> > > > > Remove i2c_set_clientdata() from the probe function, since
> > > > > i2c_get_clientdata() is not used anymore.
> > > >
> > > > Looks good overall.
> > > > A few comments inline.
> > > >
> > > > >
> > > > > Signed-off-by: Théo Borém Fabris <theobf@....br>
> > > > > ---
> > > > > drivers/iio/dac/max5821.c | 30 ++++++++++++++++--------------
> > > > > 1 file changed, 16 insertions(+), 14 deletions(-)
> > > > >
> > > > > diff --git a/drivers/iio/dac/max5821.c b/drivers/iio/dac/max5821.c
> > > > > index bd6e75699a63..44c04ae70b32 100644
> > > > > --- a/drivers/iio/dac/max5821.c
> > > > > +++ b/drivers/iio/dac/max5821.c
> > > > > @@ -294,6 +294,13 @@ static const struct iio_info max5821_info = {
> > > > > .write_raw = max5821_write_raw,
> > > > > };
> > > > >
> > > > > +static void max5821_regulator_disable(void *data)
> > > > > +{
> > > > > + struct regulator *rdata = data;
> > > > > +
> > > > > + regulator_disable(rdata);
> > > >
> > > > This can be simplified a bit:
> > > >
> > > > static void max5821_regulator_disable(void *reg)
> > > > {
> > > > regulator_disable(reg);
> > > > }
> > > >
> > > > I used to do explicit casting, but then I also figured that it's not necessary.
> > > >
> > > Ok.
> > >
> > > > > +}
> > > > > +
> > > > > static int max5821_probe(struct i2c_client *client,
> > > > > const struct i2c_device_id *id)
> > > > > {
> > > > > @@ -306,7 +313,6 @@ static int max5821_probe(struct i2c_client *client,
> > > > > if (!indio_dev)
> > > > > return -ENOMEM;
> > > > > data = iio_priv(indio_dev);
> > > > > - i2c_set_clientdata(client, indio_dev);
> > > > > data->client = client;
> > > > > mutex_init(&data->lock);
> > > > >
> > > > > @@ -331,6 +337,14 @@ static int max5821_probe(struct i2c_client *client,
> > > > > goto error_free_reg;
> > > > > }
> > > > >
> > > > > + ret = devm_add_action_or_reset(&client->dev, max5821_regulator_disable,
> > > > > + data->vref_reg);
> > > > > + if (ret) {
> > > > > + dev_err(&client->dev,
> > > > > + "Failed to add action to managed regulator: %d\n", ret);
> > > > > + goto error_disable_reg;
> > > >
> > > > return ret;
> > > >
> > > > devm_add_action_or_reset() should call max5821_regulator_disable() in
> > > > case of error
> > > >
> > > Ok.
> > >
> > > > > + }
> > > > > +
> > > > > ret = regulator_get_voltage(data->vref_reg);
> > > > > if (ret < 0) {
> > > > > dev_err(&client->dev,
> > > > > @@ -346,7 +360,7 @@ static int max5821_probe(struct i2c_client *client,
> > > > > indio_dev->modes = INDIO_DIRECT_MODE;
> > > > > indio_dev->info = &max5821_info;
> > > > >
> > > > > - return iio_device_register(indio_dev);
> > > > > + return devm_iio_device_register(&client->dev, indio_dev);
> > > > >
> > > > > error_disable_reg:
> > > >
> > > > This entire goto block should be removed.
> > > > The idea of using only devm_ functions is to not have these goto statements.
> > > >
> > > I thought the action added via devm_add_action (and devres_add) was called only
> > > on driver detach, thus the error_disable_reg label would be necessary
> > > to handle the
> >
> > devm_add_action() yes
> > this is devm_add_action_or_reset() which looks like this:
> >
> > static inline int devm_add_action_or_reset(struct device *dev,
> > void (*action)(void *), void *data)
> > {
> > int ret;
> >
> > ret = devm_add_action(dev, action, data);
> > if (ret)
> > action(data);
> >
> > return ret;
> > }
> >
> > it can be found in "include/linux/device.h"
> >
> > > possible error on regulator_get_voltage. Could you please clarify for
> > > me when does
> > > a driver detach happen?
> >
> > a driver detach happens when:
> > * the kmod is unloaded (assuming the driver is running as a kmod)
> > * manually unbinding the driver from sysfs ;
> > a quick article about this [it's for USB, but other interfaces use
> > the same mechanism]:
> > https://lwn.net/Articles/143397/
> > there should be something under /sys/bus/spi/drivers/xxxx/unbind
> > * when the system powers down (reboots)
> > * maybe there is some other new method to do this [that I don't know about]
> >
> Thank you so much.
>
> So, should this goto error_disable_reg be replaced by
> "regulator_disable(.); return ret;"?
> ret = regulator_get_voltage(data->vref_reg);
> if (ret < 0) {
> dev_err(&client->dev,
> "Failed to get voltage on regulator: %d\n", ret);
> goto error_disable_reg;
> }
This is sufficient:
[ No extra regulator_disable() is required; regulator_disable() gets
called via max5821_regulator_disable() on the error path ]
ret = devm_add_action_or_reset(&client->dev, max5821_regulator_disable,
data->vref_reg);
if (ret) {
dev_err(&client->dev,
"Failed to add action to managed regulator: %d\n", ret);
return ret;
}
>
> > >
> > > Thanks for your reply,
> > > Théo
> > >
> > > > > regulator_disable(data->vref_reg);
> > > > > @@ -356,17 +370,6 @@ static int max5821_probe(struct i2c_client *client,
> > > > > return ret;
> > > > > }
> > > > >
> > > > > -static int max5821_remove(struct i2c_client *client)
> > > > > -{
> > > > > - struct iio_dev *indio_dev = i2c_get_clientdata(client);
> > > > > - struct max5821_data *data = iio_priv(indio_dev);
> > > > > -
> > > > > - iio_device_unregister(indio_dev);
> > > > > - regulator_disable(data->vref_reg);
> > > > > -
> > > > > - return 0;
> > > > > -}
> > > > > -
> > > > > static const struct i2c_device_id max5821_id[] = {
> > > > > { "max5821", ID_MAX5821 },
> > > > > { }
> > > > > @@ -386,7 +389,6 @@ static struct i2c_driver max5821_driver = {
> > > > > .pm = &max5821_pm_ops,
> > > > > },
> > > > > .probe = max5821_probe,
> > > > > - .remove = max5821_remove,
> > > > > .id_table = max5821_id,
> > > > > };
> > > > > module_i2c_driver(max5821_driver);
> > > > > --
> > > > > 2.20.1
> > > > >
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