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Subject[PATCH v2] gpio: mt7621: support gpio-line-names property
Date
The default handling of the gpio-line-names property by the
gpiolib-of implementation does not work with the multiple
gpiochip banks per device structure used by the gpio-mt7621
driver.

This commit adds driver level support for the device tree
property so that GPIO lines can be assigned friendly names.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
---
Hi,

This driver has three gpiochips with 32 gpios each. Core implmentation
got gpio's repeated along each gpio chip if chip.names is not assigned.
To avoid this behaviour driver will set this names as empty or
with desired friendly line names. Consider the following sample with
minimal entries for the first chip with this patch changes applied:

&gpio {
gpio-line-names = "", "", "", "",
"", "", "SFP LOS", "extcon port5 PoE compat",
"SFP module def0", "LED blue SFP", "SFP tx disable", "",
"switch USB power", "mode", "", "buzzer",
"LED blue pwr", "switch port5 PoE out", "reset";
};

gpioinfo
gpiochip0 - 32 lines:
line 0: unnamed unused output active-high
line 1: unnamed unused input active-high
line 2: unnamed unused input active-high
line 3: unnamed unused input active-high
line 4: unnamed unused input active-high
line 5: unnamed unused input active-high
line 6: "SFP LOS" "los" input active-high [used]
line 7: "extcon port5 PoE compat" unused input active-high
line 8: "SFP module def0" "mod-def0" input active-low [used]
line 9: "LED blue SFP" "blue:sfp" output active-high [used]
line 10: "SFP tx disable" "tx-disable" output active-high [used]
line 11: unnamed unused output active-high
line 12: "switch USB power" "usb_power" output active-high [used]
line 13: "mode" "mode" input active-high [used]
line 14: unnamed unused input active-high
line 15: "buzzer" "buzzer" output active-high [used]
line 16: "LED blue pwr" "blue:pwr" output active-high [used]
line 17: "switch port5 PoE out" "sysfs" input active-high [used]
line 18: "reset" "reset" input active-high [used]
line 19: unnamed unused input active-high
line 20: unnamed unused input active-high
line 21: unnamed unused input active-high
line 22: unnamed unused input active-high
line 23: unnamed unused input active-high
line 24: unnamed unused input active-high
line 25: unnamed unused input active-high
line 26: unnamed unused input active-high
line 27: unnamed unused input active-high
line 28: unnamed unused input active-high
line 29: unnamed unused input active-high
line 30: unnamed unused input active-high
line 31: unnamed unused input active-high
gpiochip1 - 32 lines:
line 0: unnamed unused input active-high
line 1: unnamed unused input active-high
...
line 31: unnamed unused input active-high
gpiochip2 - 32 lines:
line 0: unnamed unused input active-high
line 1: unnamed unused input active-high
...
line 31: unnamed unused input active-high

To avoid gpiochip1 and gpiochip2 entries repeated with this
minimal lines definition change, we assign empty reserved
'names' in driver code.

Note that we also don't want to to prevent the driver from
succeeding at probe due to an error in the gpio-line-names
property and the ENODATA error is considered a valid result
to terminate any further labeling so there is no need for
an error message in that case. Other error results are
unexpected so an error message indicating the consequence
of the error is appropriate here.

Changes in v2:
- 'mediatek_gpio_set_names' returns -ENOMEM in case of OOM.
- Caller checks 'mediatek_gpio_set_names' return value.

Thanks in advance for your time.

Best regards,
Sergio Paracuellos

drivers/gpio/gpio-mt7621.c | 45 ++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)

diff --git a/drivers/gpio/gpio-mt7621.c b/drivers/gpio/gpio-mt7621.c
index 82fb20dca53a..7fc9e3c1ce10 100644
--- a/drivers/gpio/gpio-mt7621.c
+++ b/drivers/gpio/gpio-mt7621.c
@@ -206,6 +206,47 @@ mediatek_gpio_xlate(struct gpio_chip *chip,
return gpio % MTK_BANK_WIDTH;
}

+static int
+mediatek_gpio_set_names(struct device *dev, struct mtk_gc *rg)
+{
+ struct device_node *np = dev->of_node;
+ const char **names;
+ int nstrings, base;
+ unsigned int i;
+
+ names = devm_kcalloc(dev, MTK_BANK_WIDTH, sizeof(*names),
+ GFP_KERNEL);
+ if (!names)
+ return -ENOMEM;
+
+ base = rg->bank * MTK_BANK_WIDTH;
+ nstrings = of_property_count_strings(np, "gpio-line-names");
+ if (nstrings <= base)
+ goto assign_names;
+
+ for (i = 0; i < MTK_BANK_WIDTH; i++) {
+ const char *name;
+ int ret;
+
+ ret = of_property_read_string_index(np, "gpio-line-names",
+ base + i, &name);
+ if (ret) {
+ if (ret != -ENODATA)
+ dev_err(dev, "unable to name line %d: %d\n",
+ base + i, ret);
+ break;
+ }
+
+ if (*name)
+ names[i] = name;
+ }
+
+assign_names:
+ rg->chip.names = names;
+
+ return 0;
+}
+
static int
mediatek_gpio_bank_probe(struct device *dev,
struct device_node *node, int bank)
@@ -241,6 +282,10 @@ mediatek_gpio_bank_probe(struct device *dev,
if (!rg->chip.label)
return -ENOMEM;

+ ret = mediatek_gpio_set_names(dev, rg);
+ if (ret)
+ return ret;
+
rg->irq_chip.name = dev_name(dev);
rg->irq_chip.parent_device = dev;
rg->irq_chip.irq_unmask = mediatek_gpio_irq_unmask;
--
2.25.1
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