Messages in this thread | | | From | Andy Shevchenko <> | Date | Mon, 21 Jun 2021 20:43:21 +0300 | Subject | Re: [PATCH v5 2/2] gpio: gpio-cascade: add generic GPIO cascade |
| |
On Mon, Jun 21, 2021 at 8:25 PM Mauri Sandberg <maukka@ext.kapsi.fi> wrote: > > Adds support for a building cascades of GPIO lines. That is, it allows
for building
> setups when there is one upstream line and multiple cascaded lines, out > of which one can be chosen at a time. The status of the upstream line > can be conveyd to the selected cascaded line or, vice versa, the status
conveyed
> of the cascaded line can be conveyed to the upstream line. > > A gpio-mux is being used to select, which cascaded GPIO line is being > used at any given time. > > At the moment only input direction is supported. In future it should be > possible to add support for output direction, too.
Since in parallel there is a discussion about the virtio-gpio interface, how will this work with it?
> +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * A generic GPIO cascade driver > + * > + * Copyright (C) 2021 Mauri Sandberg <maukka@ext.kapsi.fi> > + * > + * This allows building cascades of GPIO lines in a manner illustrated > + * below: > + * > + * /|---- Cascaded GPIO line 0 > + * Upstream | |---- Cascaded GPIO line 1 > + * GPIO line ----+ | . > + * | | . > + * \|---- Cascaded GPIO line n > + * > + * A gpio-mux is being used to select, which cascaded line is being > + * addressed at any given time. > + * > + * At the moment only input mode is supported due to lack of means for > + * testing output functionality. At least theoretically output should be > + * possible with an open drain constructions. > + */
...
> +static int gpio_cascade_get_value(struct gpio_chip *gc, unsigned int offset) > +{ > + struct gpio_cascade *cas; > + int ret;
> + cas = chip_to_cascade(gc);
Doing this in the definition block above will save a LOC.
> + ret = mux_control_select(cas->mux_control, offset); > + if (ret) > + return ret; > + > + ret = gpiod_get_value(cas->upstream_line); > + mux_control_deselect(cas->mux_control); > + return ret; > +}
...
> + struct device_node *np = pdev->dev.of_node;
Nope, see below.
...
> + cas = devm_kzalloc(dev, sizeof(struct gpio_cascade), GFP_KERNEL);
sizeof(*cas)
> + if (cas == NULL)
if (!cas)
> + return -ENOMEM;
...
> + mc = devm_mux_control_get(dev, NULL); > + if (IS_ERR(mc)) { > + err = (int) PTR_ERR(mc); > + if (err != -EPROBE_DEFER) > + dev_err(dev, "unable to get mux-control: %d\n", err); > + return err;
Oh là là! No, the explicit castings are bad. besides the fact that all above can be replaced by
return dev_err_probe(...);
> + } > + > + cas->mux_control = mc; > + upstream = devm_gpiod_get(dev, "upstream", GPIOD_IN); > + if (IS_ERR(upstream)) {
> + err = (int) PTR_ERR(upstream); > + dev_err(dev, "unable to claim upstream GPIO line: %d\n", err);
No castings. Use proper printf() specifiers.
> + return err; > + }
...
> + gc->of_node = np;
This should be guarded by CONFIG_OF_GPIO. And no need to use the np temporary variable for one use like this.
...
> + err = gpiochip_add(&cas->gpio_chip);
Why not the devm variant?
> + if (err) { > + dev_err(dev, "unable to add gpio chip, err=%d\n", err); > + return err; > + }
...
> + dev_info(dev, "registered %u cascaded GPIO lines\n", gc->ngpio);
No, we don't pollute logs when everything is fine.
...
> +static const struct of_device_id gpio_cascade_id[] = { > + { > + .compatible = "gpio-cascade",
> + .data = NULL,
Redundant.
> + },
All above may consume only a single LOC.
> + { /* sentinel */ } > +}; > +MODULE_DEVICE_TABLE(of, gpio_cascade_id);
-- With Best Regards, Andy Shevchenko
| |