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

Dmitry Torokhov
2022-11-04T18:52:35Z

Hi Andy,

On Fri, Nov 04, 2022 at 07:17:27PM +0200, Andy Shevchenko wrote:
> On Thu, Nov 03, 2022 at 11:10:15PM -0700, 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.
>
> ...
>
> > +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)
> > {
>
> > + struct gpio_desc *desc = ERR_PTR(-ENOENT);
>
> No need, just return directly.
>
> > + dev_dbg(consumer, "GPIO lookup for consumer %s in node '%s'\n",
> > + con_id, fwnode_get_name(fwnode));
>
> %pfwP ?

OK. Although, I think I like %pfw (without 'P') better as it gives
results like:

/soc/i2c@11007000/edp-bridge@8

or

\_SB.PCI0.I2C1.D010

which should help identifying the exact node.

>
> > +
> > + /* Using device tree? */
> > if (is_of_node(fwnode)) {
> > + dev_dbg(consumer, "using device tree for GPIO lookup\n");
> > + desc = of_find_gpio(to_of_node(fwnode),
> > + con_id, idx, lookupflags);
> > } else if (is_acpi_node(fwnode)) {
>
> With direct return, no need for 'else' here.

When we have several branches of equal weight I prefer not to have
early/inline returns, but I can add:

} else {
desc = ERR_PTR(-ENOENT);
}

at the end, what do you think?

>
> > + dev_dbg(consumer, "using ACPI for GPIO lookup\n");
> > + desc = acpi_find_gpio(fwnode, con_id, idx, flags, lookupflags);
> > }
> >
> > + return desc;
> > +}
>
> ...
>
> > +static struct gpio_desc *gpiod_find_and_request(struct device *consumer,
> > + struct fwnode_handle *fwnode,
> > + const char *con_id,
> > + unsigned int idx,
> > + enum gpiod_flags flags,
> > + const char *label,
> > + bool platform_lookup_allowed)
> > +{
>
> > + struct gpio_desc *desc = ERR_PTR(-ENOENT);
>
> We can get rid of the assignment, see below.
>
>
> > + unsigned long lookupflags;
> > + int ret;
>
> > + if (fwnode)
>
> Do we need this check?

Yes, I would prefer to have it as it clearly informs the reader that we
are only doing lookup by node if we actually have a node.

gpiod_find_and_request() expects that it gets a valid node and in the
followup change it will be dereferencing fwnode without checking for
NULL-ness.

>
> Debug message above (when %pfw is used) would be even useful when
> fwnode == NULL.
>
> > + desc = gpiod_find_by_fwnode(fwnode, consumer, con_id, idx,
> > + &flags, &lookupflags);
>
> > +
>
> The blank line can be removed after above comments being addressed.
>
> > + 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;
> > + }
> > +
> > + /*
> > + * If a connection label was passed use that, else attempt to use
> > + * the device name as label
> > + */
> > ret = gpiod_request(desc, label);
> > + if (ret) {
> > + if (!(ret == -EBUSY && flags & GPIOD_FLAGS_BIT_NONEXCLUSIVE))
> > + return ERR_PTR(ret);
> > +
> > + /*
> > + * This happens when there are several consumers for
> > + * the same GPIO line: we just return here without
> > + * further initialization. It is a bit of a hack.
> > + * This is necessary to support fixed regulators.
> > + *
> > + * FIXME: Make this more sane and safe.
> > + */
>
> > + dev_info(consumer,
> > + "nonexclusive access to GPIO for %s\n", con_id);
>
> Cam be one line.

I still have not embraced the new 100 columns limit. Linus, Bart, are
you OK with moving to 100 or do you want to stay with 80 for a while?

>
> > + return desc;
> > + }
> >
> > + ret = gpiod_configure_flags(desc, con_id, lookupflags, flags);
> > if (ret < 0) {
> > + dev_dbg(consumer, "setup of GPIO %s failed\n", con_id);
> > gpiod_put(desc);
> > return ERR_PTR(ret);
> > }
>
> ...
>
> > struct gpio_desc *fwnode_gpiod_get_index(struct fwnode_handle *fwnode,
> > + const char *con_id,
> > + int index,
> > enum gpiod_flags flags,
> > const char *label)
> > {
> >
>
> Unnecessary blank line?

Indeed, I'll fix it.

>
> > + return gpiod_find_and_request(NULL, fwnode, con_id, index, flags, label,
> > + false);
>
> Can be one line.

Yep, depending on 80/100 column answer.

Thanks for the review!

--
Dmitry