Re: [PATCH v2 5/6] gpiolib: consolidate GPIO lookups

Dmitry Torokhov
2022-11-09T19:00:45Z

On Wed, Nov 09, 2022 at 01:25:06PM +0200, Andy Shevchenko wrote:
> On Tue, Nov 08, 2022 at 04:26:50PM -0800, Dmitry Torokhov wrote:
> > Ensure that all paths to obtain/look up GPIOD from generic
> > consumer-visible APIs go through the new gpiod_find_and_request()
> > helper, so that we can easily extend it with support for new firmware
> > mechanisms.
> >
> > The only exception is OF-specific [devm_]gpiod_get_from_of_node() API
> > that is still being used by a couple of drivers and will be removed as
> > soon as patches converting them to use generic fwnode/device APIs are
> > accepted.
>
> ...
>
> > +static struct gpio_desc *gpiod_find_by_fwnode(struct fwnode_handle *fwnode,
> > + struct device *consumer,
> > + const char *con_id,
> > + unsigned int idx,
> > + enum gpiod_flags *flags,
> > + unsigned long *lookupflags)
> > {
> > - unsigned long lflags = GPIO_LOOKUP_FLAGS_DEFAULT;
>
> > - struct gpio_desc *desc = ERR_PTR(-ENODEV);
>
> Not sure why this is needed. Now I see that else branch has been changed,
> but looking closer to it, we can drop it completely, while leaving this
> line untouched, correct?

Yes. I believe removing an initializer and doing a series of if/else
if/else was discussed and [soft] agreed-on in the previous review cycle,
but I can change it back.

I think we still need to have it return -ENOENT and not -ENODEV/-EINVAL
so that we can fall back to GPIO lookup tables when dealing with an
unsupported node type.

>
> > - int ret;
> > + struct gpio_desc *desc;
> >
> > + dev_dbg(consumer, "GPIO lookup for consumer %s in node '%pfw'\n",
> > + con_id, fwnode);
> > +
> > + /* Using device tree? */
> > if (is_of_node(fwnode)) {
> > - desc = gpiod_get_from_of_node(to_of_node(fwnode),
> > - propname, index,
> > - dflags,
> > - label);
> > - return desc;
> > + dev_dbg(consumer, "using device tree for GPIO lookup\n");
> > + desc = of_find_gpio(to_of_node(fwnode),
> > + con_id, idx, lookupflags);
>
> At least con_id can be placed on the previous line.

OK, I made it all 1 line.

>
> > } else if (is_acpi_node(fwnode)) {
> > - desc = acpi_node_get_gpiod(fwnode, propname, index,
> > - &lflags, &dflags);
> > - if (IS_ERR(desc))
> > - return desc;
> > + dev_dbg(consumer, "using ACPI for GPIO lookup\n");
> > + desc = acpi_find_gpio(fwnode, con_id, idx, flags, lookupflags);
> > } else {
> > - return ERR_PTR(-EINVAL);
> > + desc = ERR_PTR(-ENOENT);
> > }
> >
> > - /* Currently only ACPI takes this path */
> > + return desc;
> > +}
>
> ...
>
> > + struct gpio_desc *desc = ERR_PTR(-ENOENT);
> > + unsigned long lookupflags;
> > + int ret;
>
> > + if (!IS_ERR_OR_NULL(fwnode))
>
> I think this is superfluous check.
>
> Now in the form of this series, you have only a single dev_dbg() that tries to
> dereference it. Do we really need to have it there, since every branch has its
> own dev_dbg() anyway?

As I mentioned, I like to keep this check to show the reader that we
should only descend into gpiod_find_by_fwnode() if we have a valid
fwnode. It is less about code generation and more about the intent.

I did change the logging to remove extra dev_dbg(). We will lose message
when dealing with unsupported node type, but that should not really
happen in practice.

>
> > + desc = gpiod_find_by_fwnode(fwnode, consumer, con_id, idx,
> > + &flags, &lookupflags);
>
> > +
>
> This blank line can be dropped after addressing above.
>
> > + if (gpiod_not_found(desc) && platform_lookup_allowed) {
> > + /*
> > + * Either we are not using DT or ACPI, or their lookup did not
> > + * return a result. In that case, use platform lookup as a
> > + * fallback.
> > + */
> > + dev_dbg(consumer, "using lookup tables for GPIO lookup\n");
> > + desc = gpiod_find(consumer, con_id, idx, &lookupflags);
> > + }
> > +
> > + if (IS_ERR(desc)) {
> > + dev_dbg(consumer, "No GPIO consumer %s found\n", con_id);
> > + return desc;
> > + }
>
> ...
>
> > + return gpiod_find_and_request(NULL, fwnode, con_id, index, flags, label,
> > + false);
>
> One line?

OK :)

>
> ...
>
> > + return gpiod_find_and_request(dev, fwnode, con_id, idx, flags, label,
> > + true);
>
> One line?

OK.

Thanks,

--
Dmitry