On Fri, Dec 19, 2014 at 2:08 AM, Benoit Parrot [off-list ref] wrote:

Alexandre Courbot [off-list ref] wrote on Wed [2014-Dec-17 17:41:51 +0900]:

quoted

Looks ok to me. I have a few nits below, but otherwise I am happy with
how it turned out:

Reviewed-by: Alexandre Courbot <redacted>

I'll add this to the next version.

quoted

Thanks for your patience with this!

On Sat, Dec 13, 2014 at 7:07 AM, Benoit Parrot [off-list ref] wrote:

quoted

Based on Boris Brezillion's work this is a reworked patch
of his initial GPIO hogging mechanism.
This patch provides a way to initally configure specific GPIO

s/initally/initially

quoted

when the gpio controller is probed.

GPIO in capitals please.

quoted

The actual DT scanning to collect the GPIO specific data is performed
as part of the gpiochip_add().

d/the

quoted

The purpose of this is to allows specific GPIOs to be configured

s/allows/allow

quoted

without any driver specific code.
This particularly useful because board design are getting

This is particularly

quoted

increasingly complex and given SoC pins can now have upward
of

s/upward of/up to?

well i meant more than 10 I think in some cases we have 13.

quoted

quoted

10 mux values a lot of connections are now dependent on

seems like a comma is missing here.

quoted

external IO muxes to switch various modes and combination.

not sure what a combination is in that context.

quoted

Specific drivers should not necessarily need to be aware of
what accounts to a specific board implementation. This board level
"description" should be best kept as part of the dts file.

Signed-off-by: Benoit Parrot <redacted>
---
Changes since v3:
 * Relocated the non-DT "hog" function to gpiolib.c.
 * Rename some of the function to be clearer and remove _ prefixes.
 * Replace the gpiod_request/gpiod_put usage with
   gpiochip_request_own_desc/free_own_desc version instead.
 * Refactor some of the logic to better handle error condition/reporting
 * Renamed the "direction" DT properties to "state".

 drivers/gpio/gpiolib-of.c | 119 ++++++++++++++++++++++++++++++++++++++++++
 drivers/gpio/gpiolib.c    | 128 ++++++++++++++++++++++++++++++++++++++--------
 drivers/gpio/gpiolib.h    |   3 ++
 3 files changed, 230 insertions(+), 20 deletions(-)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 604dbe6..5422216 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c

@@ -22,6 +22,7 @@
 #include <linux/of_gpio.h>
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/slab.h>
+#include <linux/gpio/machine.h>

 #include "gpiolib.h"

@@ -111,6 +112,122 @@ int of_get_named_gpio_flags(struct device_node *np, const char *list_name,
 EXPORT_SYMBOL(of_get_named_gpio_flags);

 /**
+ * of_get_gpio_hog() - Get a GPIO hog descriptor, names and flags for GPIO API
+ * @np:                device node to get GPIO from
+ * @name:      GPIO line name
+ * @flags:     a flags pointer to fill in
+ *
+ * Returns GPIO descriptor to use with Linux GPIO API, or one of the errno
+ * value on the error condition.
+ */
+
+static struct gpio_desc *of_get_gpio_hog(struct device_node *np,
+                                 const char **name,
+                                 enum gpio_lookup_flags *lflags,
+                                 enum gpiod_flags *dflags)
+{
+       struct device_node *chip_np;
+       enum of_gpio_flags xlate_flags;
+       struct gpio_desc *desc;
+       const char *dir_val;
+       struct gg_data gg_data = {
+               .flags = &xlate_flags,
+               .out_gpio = NULL,

out_gpio will be set to NULL if you don't specify it, so you don't
need this last line.

ok

quoted

quoted

+       };
+       u32 tmp;
+       int i, ret;
+
+       chip_np = np->parent;
+       if (!chip_np)
+               return ERR_PTR(-EINVAL);
+
+       xlate_flags = 0;
+       *lflags = 0;
+       *dflags = 0;
+
+       ret = of_property_read_u32(chip_np, "#gpio-cells", &tmp);
+       if (ret)
+               return ERR_PTR(ret);
+
+       if (tmp > MAX_PHANDLE_ARGS)
+               return ERR_PTR(-EINVAL);
+
+       gg_data.gpiospec.args_count = tmp;
+       gg_data.gpiospec.np = chip_np;
+       for (i = 0; i < tmp; i++) {
+               ret = of_property_read_u32_index(np, "gpios", i,
+                                          &gg_data.gpiospec.args[i]);
+               if (ret)
+                       return ERR_PTR(ret);
+       }
+
+       gpiochip_find(&gg_data, of_gpiochip_find_and_xlate);
+       if (!gg_data.out_gpio) {
+               if (np->parent == np)
+                       return ERR_PTR(-ENXIO);
+               else
+                       return ERR_PTR(-EPROBE_DEFER);
+       }
+
+       if (xlate_flags & OF_GPIO_ACTIVE_LOW)
+               *lflags |= GPIO_ACTIVE_LOW;
+
+       if (of_property_read_string(np, "state", &dir_val)) {
+               pr_warn("%s: GPIO:%d (%s): no hogging state specified, bailing out\n",
+                        __func__, desc_to_gpio(gg_data.out_gpio), np->name);
+               return ERR_PTR(-EINVAL);
+       }
+
+       if (!strcmp(dir_val, "input"))
+               *dflags |= GPIOD_IN;
+       else if (!strcmp(dir_val, "output-low"))
+               *dflags |= GPIOD_OUT_LOW;
+       else if (!strcmp(dir_val, "output-high"))
+               *dflags |= GPIOD_OUT_HIGH;
+       else {
+               pr_warn("%s: GPIO:%d (%s): invalid state '%s' requested, bailing out\n",
+                        __func__, desc_to_gpio(gg_data.out_gpio),
+                       np->name, dir_val);
+               return ERR_PTR(-EINVAL);
+       }
+
+       if (name && of_property_read_string(np, "line-name", name))
+               *name = np->name;
+
+       desc = gg_data.out_gpio;
+
+       return desc;
+}
+
+/**
+ * of_gpiochip_scan_hogs - Scan gpio-controller and apply GPIO hog as requested
+ * @chip:      gpio chip to act on
+ *
+ * This is only used by of_gpiochip_add to request/set GPIO initial
+ * configuration.
+ */
+static void of_gpiochip_scan_hogs(struct gpio_chip *chip)
+{
+       struct gpio_desc *desc = NULL;
+       struct device_node *np;
+       const char *name;
+       enum gpio_lookup_flags lflags;
+       enum gpiod_flags dflags;
+
+       for_each_child_of_node(chip->dev->of_node, np) {

As I was backporting this to 3.14 for my own purpose.
I encountered a NULL pointer dereference here.
In 3.14 chip->dev (which is optional) is NULL at least on my platform.
I had to change the above line to:

       for_each_child_of_node(chip->of_node, np) {

Would you recommend the same change here?

That looks ok, yes. IIRC chip->of_node is precisely here because
chip->dev might be NULL sometimes.
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