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SubjectRe: [PATCH v2] gpio: mt7621: support gpio-line-names property
On Sat, Jul 3, 2021 at 9:36 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
>
> On Sat, Jul 3, 2021 at 3:51 PM Sergio Paracuellos
> <sergio.paracuellos@gmail.com> wrote:
> > On Sat, Jul 3, 2021 at 2:05 PM Sergio Paracuellos
> > <sergio.paracuellos@gmail.com> wrote:
> > > On Sat, Jul 3, 2021 at 1:32 PM Andy Shevchenko
> > > <andy.shevchenko@gmail.com> wrote:
> > > > On Sat, Jul 3, 2021 at 2:06 PM Sergio Paracuellos
> > > > <sergio.paracuellos@gmail.com> wrote:
> > > > > On Fri, Jul 2, 2021 at 1:30 PM Sergio Paracuellos
> > > > > <sergio.paracuellos@gmail.com> wrote:
> > > >
> > > > ...
> > > >
> > > > > - ret = devprop_gpiochip_set_names(gc);
> > > > > + ret = devprop_gpiochip_set_names(gc, 0);
> > > >
> > > > I had been expecting that this parameter would be in the field of the gpiochip.
> > > >
> > > > ...
> > >
> > > If doing it in that way is preferred, I have no problem at all. But in
> > > that case I think there is no need for a new
> > > 'devprop_gpiochip_set_names_base' and we can assume for all drivers to
> > > be zero and if is set taking it into account directly in
> > > devprop_gpiochip_set_names function? Is this what you mean by having
> > > this field added there??
>
> The below is closer to what I meant, yes. I have not much time to look
> into the details, but I don't have objections about what you suggested
> below. Additional comments there as well.

Thanks for your time and review, Andy. Let's wait to see if Linus and
Bartosz are also ok with this approach.

>
> > How about something like this?
> >
> > diff --git a/drivers/gpio/gpio-mt7621.c b/drivers/gpio/gpio-mt7621.c
> > index 82fb20dca53a..5854a9343491 100644
> > --- a/drivers/gpio/gpio-mt7621.c
> > +++ b/drivers/gpio/gpio-mt7621.c
> > @@ -241,6 +241,7 @@ mediatek_gpio_bank_probe(struct device *dev,
> > if (!rg->chip.label)
> > return -ENOMEM;
> >
> > + rg->chip.offset = bank * MTK_BANK_WIDTH;
> > rg->irq_chip.name = dev_name(dev);
> > rg->irq_chip.parent_device = dev;
> > rg->irq_chip.irq_unmask = mediatek_gpio_irq_unmask;
>
> Obviously it should be a separate patch :-)

Of course :). I will include one separate patch per driver using the
custom set names stuff: gpio-mt7621 and gpio-brcmstb. I don't know if
any other one is also following that wrong pattern.

>
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index 6e3c4d7a7d14..0587f46b7c22 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -380,10 +380,10 @@ static int devprop_gpiochip_set_names(struct
> > gpio_chip *chip)
> > return 0;
> >
> > count = device_property_string_array_count(dev, "gpio-line-names");
> > - if (count < 0)
>
> > + if (count < 0 || count <= chip->offset)
>
> Please, split it into two conditionals and add a comment to the second one.

For sure I will do, thanks.

>
> > return 0;
> >
> > - if (count > gdev->ngpio) {
> > + if (count > gdev->ngpio && chip->offset == 0) {
> > dev_warn(&gdev->dev, "gpio-line-names is length %d but
> > should be at most length %d",
> > count, gdev->ngpio);
> > count = gdev->ngpio;
> > @@ -401,8 +401,9 @@ static int devprop_gpiochip_set_names(struct
> > gpio_chip *chip)
> > return ret;
> > }
> >
> > + count = (chip->offset >= count) ? (chip->offset - count) : count;
>
> Too many parentheses.

Ok, I will also change this.

>
> > for (i = 0; i < count; i++)
> > - gdev->descs[i].name = names[i];
> > + gdev->descs[i].name = names[chip->offset + i];
> >
> > kfree(names);
> >
> > diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
> > index 4a7e295c3640..39e0786586f6 100644
> > --- a/include/linux/gpio/driver.h
> > +++ b/include/linux/gpio/driver.h
> > @@ -312,6 +312,9 @@ struct gpio_irq_chip {
> > * get rid of the static GPIO number space in the long run.
> > * @ngpio: the number of GPIOs handled by this controller; the last GPIO
> > * handled is (base + ngpio - 1).
> > + * @offset: when multiple gpio chips belong to the same device this
> > + * can be used as offset within the device so friendly names can
> > + * be properly assigned.
> > * @names: if set, must be an array of strings to use as alternative
> > * names for the GPIOs in this chip. Any entry in the array
> > * may be NULL if there is no alias for the GPIO, however the
> > @@ -398,6 +401,7 @@ struct gpio_chip {
> >
> > int base;
> > u16 ngpio;
> > + int offset;
>
> u16 (as ngpio has that type)
>
> > const char *const *names;
> > bool can_sleep;
> >
> >
> > Does this sound reasonable?

So the gpiolib related patch updated code with your proposed changes
looks as follows:

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 6e3c4d7a7d14..0c773d9ef292 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -383,7 +383,18 @@ static int devprop_gpiochip_set_names(struct
gpio_chip *chip)
if (count < 0)
return 0;

- if (count > gdev->ngpio) {
+ /*
+ * When offset is set in the driver side we assume the driver internally
+ * is using more than one gpiochip per the same device. We have to stop
+ * setting friendly names if the specified ones with 'gpio-line-names'
+ * are less than the offset in the device itself. This means all the
+ * lines are not present for every single pin within all the internal
+ * gpiochips.
+ */
+ if (count <= chip->offset)
+ return 0;
+
+ if (count > gdev->ngpio && chip->offset == 0) {
dev_warn(&gdev->dev, "gpio-line-names is length %d but
should be at most length %d",
count, gdev->ngpio);
count = gdev->ngpio;
@@ -401,8 +412,9 @@ static int devprop_gpiochip_set_names(struct
gpio_chip *chip)
return ret;
}

+ count = (chip->offset >= count) ? chip->offset - count : count;
for (i = 0; i < count; i++)
- gdev->descs[i].name = names[i];
+ gdev->descs[i].name = names[chip->offset + i];

kfree(names);

diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 4a7e295c3640..7a77f533d8fe 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -312,6 +312,9 @@ struct gpio_irq_chip {
* get rid of the static GPIO number space in the long run.
* @ngpio: the number of GPIOs handled by this controller; the last GPIO
* handled is (base + ngpio - 1).
+ * @offset: when multiple gpio chips belong to the same device this
+ * can be used as offset within the device so friendly names can
+ * be properly assigned.
* @names: if set, must be an array of strings to use as alternative
* names for the GPIOs in this chip. Any entry in the array
* may be NULL if there is no alias for the GPIO, however the
@@ -398,6 +401,7 @@ struct gpio_chip {

int base;
u16 ngpio;
+ u16 offset;
const char *const *names;
bool can_sleep;

Best regards,
Sergio Paracuellos
> > > > > The problem I see with this approach is that
> > > > > 'devprop_gpiochip_set_names' already trusts in gpio_device already
> > > > > created and this happens in 'gpiochip_add_data_with_key'. So doing in
> > > > > this way force "broken drivers" to call this new
> > > > > 'devprop_gpiochip_set_names_base' function after
> > > > > 'devm_gpiochip_add_data' is called so the core code has already set up
> > > > > the friendly names repeated for all gpio chip banks and the approach
> > > > > would be to "overwrite" those in a second pass which sounds more like
> > > > > a hack than a solution.
> > > > >
> > > > > But maybe I am missing something in what you were pointing out here.
> > > >
> > > > Would the above work?
>
> --
> With Best Regards,
> Andy Shevchenko

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