Re: [PATCH v1] gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by default
On Fri, Jan 15, 2021 at 11:03 PM Saravana Kannan wrote:
>
> There are multiple instances of GPIO devictree nodes of the form:
What? Device Tree (or device tree).
> foo {
> compatible = "acme,foo";
> ...
>
> gpio0: gpio0@ {
> compatible = "acme,bar";
> ...
> gpio-controller;
> };
>
> gpio1: gpio1@ {
> compatible = "acme,bar";
> ...
> gpio-controller;
> };
>
> ...
> }
>
> bazz {
> my-gpios = < ...>;
> }
>
> Case 1: The driver for "foo" populates struct device for these gpio*
> nodes and then probes them using a driver that binds with "acme,bar".
> This lines up with how DT nodes with the "compatible" property are
> generally converted to struct devices and then registered with driver
> core to probe them. This also allows the gpio* devices to hook into all
> the driver core capabilities like runtime PM, probe deferral,
> suspend/resume ordering, device links, etc.
>
> Case 2: The driver for "foo" doesn't populate its child device nodes
> with "compatible" property and instead just loops through its child
> nodes and directly registers the GPIOs with gpiolib without ever
> populating a struct device or binding a driver to it.
>
> Drivers that follow the case 2 cause problems with fw_devlink=on. This
follow case
> is because fw_devlink will prevent bazz from probing until there's a
> struct device that has gpio0 as its fwnode (because bazz lists gpio0 as
> a GPIO supplier). Once the struct device is available, fw_devlink will
> create a device link between with gpio0 as the supplier and bazz as the
> consumer. After this point, the device link will prevent bazz from
> probing until its supplier (the gpio0 device) has bound to a driver.
> Once the supplier is bound to a driver, the probe of bazz is triggered
> automatically.
>
> Finding and refactoring all the instances of drivers that follow case 2
> will cause a lot of code churn and it not something that can be done in
it is not
> one shot. Examples of such instances are [1] [2].
>
> This patch works around this problem and avoids all the code churn by
> simply creating a stub driver to bind to the gpio_device. Since the
> gpio_device already points to the GPIO device tree node, this allows all
> the consumers to continue probing when the driver follows case 2.
>
> If/when all the old drivers are refactored, we can revert this patch.
>
> [1] - https://lore.kernel.org/lkml/20201014191235.7f71fcb4@xhacker.debian/
> [2] -
> https://lore.kernel.org/lkml/e28e1f38d87c12a3c714a6573beba...@kernel.org/
Link: tags?
...
> + of_node = gdev->dev.of_node;
This seems unused (see below).
> + fwnode = of_fwnode_handle(of_node);
I don't get this. Are you telling that dev_fwnode(>dev) is not the same?
> + fwnode_dev = get_dev_from_fwnode(fwnode);
> +
> + /*
> +* If your driver hits this warning, it's because you are directly
> +* parsing a device tree node with "compatible" property and
> +* initializing it instead of using the standard DT + device driver
> +* model of creating a struct device and then initializing it in the
> +* probe function. Please refactor your driver.
> +*/
> + if (!fwnode_dev && of_find_property(gdev->dev.of_node, "compatible"))
> {
fwnode_property_present() ?
> + chip_warn(gc, "Create a real device for %pOF\n" of_node);
%pfw ?
> + gdev->dev.fwnode = fwnode;
Why not dev_fwnode()?
> + }
> #endif
...
> +static struct device_driver gpio_drv = {
> + .name = "gpio_drv",
Can it have a better name, please?
> + .bus = _bus_type,
> + .probe = gpio_drv_probe,
> +};
--
With Best Regards,
Andy Shevchenko
Re: [PATCH v1] gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by default
Hi Saravana,
I love your patch! Yet something to improve:
[auto build test ERROR on gpio/for-next]
[also build test ERROR on v5.11-rc3 next-20210115]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url:
https://github.com/0day-ci/linux/commits/Saravana-Kannan/gpiolib-Bind-gpio_device-to-a-driver-to-enable-fw_devlink-on-by-default/20210116-050450
base: https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git
for-next
config: arm64-randconfig-r023-20210115 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project
5b42fd8dd4e7e29125a09a41a33af7c9cb57d144)
reproduce (this is a W=1 build):
wget
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O
~/bin/make.cross
chmod +x ~/bin/make.cross
# install arm64 cross compiling tool for clang build
# apt-get install binutils-aarch64-linux-gnu
#
https://github.com/0day-ci/linux/commit/8c370ef8f557575cb23e5e288c861d9447db0b3e
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review
Saravana-Kannan/gpiolib-Bind-gpio_device-to-a-driver-to-enable-fw_devlink-on-by-default/20210116-050450
git checkout 8c370ef8f557575cb23e5e288c861d9447db0b3e
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot
All errors (new ones prefixed by >>):
>> drivers/gpio/gpiolib.c:614:69: error: too few arguments to function call,
>> expected 3, have 2
if (!fwnode_dev && of_find_property(gdev->dev.of_node,
"compatible")) {
^
include/linux/compiler.h:56:47: note: expanded from macro 'if'
#define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
^~~~
include/linux/compiler.h:58:52: note: expanded from macro '__trace_if_var'
#define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) :
__trace_if_value(cond))
^~~~
include/linux/of.h:304:25: note: 'of_find_property' declared here
extern struct property *of_find_property(const struct device_node *np,
^
>> drivers/gpio/gpiolib.c:614:69: error: too few arguments to function call,
>> expected 3, have 2
if (!fwnode_dev && of_find_property(gdev->dev.of_node,
"compatible")) {
^
include/linux/compiler.h:56:47: note: expanded from macro 'if'
#define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
^~~~
include/linux/compiler.h:58:61: note: expanded from macro '__trace_if_var'
#define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) :
__trace_if_value(cond))
^~~~
include/linux/of.h:304:25: note: 'of_find_property' declared here
extern struct property *of_find_property(const struct device_node *np,
^
>> drivers/gpio/gpiolib.c:614:69: error: too few arguments to function call,
>> expected 3, have 2
if (!fwnode_dev && of_find_property(gdev->dev.of_node,
"compatible")) {
^
include/linux/compiler.h:56:47: note: expanded from macro 'if'
#define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
^~~~
include/linux/compiler.h:58:86: note: expanded from macro '__trace_if_var'
#define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) :
__trace_if_value(cond))
^~~~
include/linux/compiler.h:69:3: note: expanded from macro '__trace_if_value'
(cond) ?\
^~~~
include/linux/of.h:304:25: note: 'of_find_property' declared here
extern struct property *of_find_property(const struct device_node *np,
^
>> drivers/gpio/gpiolib.c:615:51: error: expected ')'
chip_warn(gc, "Create a real device for %pOF\n" of_node);
^
drivers/gpio/gpiolib.c:615:3: note: to match this '('
chip_warn(gc, "Create a real device for %pOF\n" of_node);
^
drivers/gpio/gpiolib.h:182:2: note: expanded from macro 'chip_warn'
dev_warn(>gpiodev->dev, "(%s): " fmt, gc->label, ##__VA_ARGS__)
^
[PATCH v1] gpiolib: Bind gpio_device to a driver to enable fw_devlink=on by default
There are multiple instances of GPIO devictree nodes of the form:
foo {
compatible = "acme,foo";
...
gpio0: gpio0@ {
compatible = "acme,bar";
...
gpio-controller;
};
gpio1: gpio1@ {
compatible = "acme,bar";
...
gpio-controller;
};
...
}
bazz {
my-gpios = < ...>;
}
Case 1: The driver for "foo" populates struct device for these gpio*
nodes and then probes them using a driver that binds with "acme,bar".
This lines up with how DT nodes with the "compatible" property are
generally converted to struct devices and then registered with driver
core to probe them. This also allows the gpio* devices to hook into all
the driver core capabilities like runtime PM, probe deferral,
suspend/resume ordering, device links, etc.
Case 2: The driver for "foo" doesn't populate its child device nodes
with "compatible" property and instead just loops through its child
nodes and directly registers the GPIOs with gpiolib without ever
populating a struct device or binding a driver to it.
Drivers that follow the case 2 cause problems with fw_devlink=on. This
is because fw_devlink will prevent bazz from probing until there's a
struct device that has gpio0 as its fwnode (because bazz lists gpio0 as
a GPIO supplier). Once the struct device is available, fw_devlink will
create a device link between with gpio0 as the supplier and bazz as the
consumer. After this point, the device link will prevent bazz from
probing until its supplier (the gpio0 device) has bound to a driver.
Once the supplier is bound to a driver, the probe of bazz is triggered
automatically.
Finding and refactoring all the instances of drivers that follow case 2
will cause a lot of code churn and it not something that can be done in
one shot. Examples of such instances are [1] [2].
This patch works around this problem and avoids all the code churn by
simply creating a stub driver to bind to the gpio_device. Since the
gpio_device already points to the GPIO device tree node, this allows all
the consumers to continue probing when the driver follows case 2.
If/when all the old drivers are refactored, we can revert this patch.
[1] - https://lore.kernel.org/lkml/20201014191235.7f71fcb4@xhacker.debian/
[2] - https://lore.kernel.org/lkml/e28e1f38d87c12a3c714a6573beba...@kernel.org/
Cc: Marc Zyngier
Cc: Jisheng Zhang
Cc: Kever Yang
Fixes: e590474768f1 ("driver core: Set fw_devlink=on by default")
Signed-off-by: Saravana Kannan
---
drivers/gpio/gpiolib.c | 37 +
1 file changed, 37 insertions(+)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index b02cc2abd3b6..36f0af42e203 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -574,6 +574,9 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void
*data,
unsignedi;
int base = gc->base;
struct gpio_device *gdev;
+ struct device_node *of_node;
+ struct fwnode_handle *fwnode;
+ struct device *fwnode_dev;
/*
* First: allocate and populate the internal stat container, and
@@ -596,6 +599,22 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void
*data,
gdev->dev.of_node = gc->of_node;
else
gc->of_node = gdev->dev.of_node;
+
+ of_node = gdev->dev.of_node;
+ fwnode = of_fwnode_handle(of_node);
+ fwnode_dev = get_dev_from_fwnode(fwnode);
+
+ /*
+* If your driver hits this warning, it's because you are directly
+* parsing a device tree node with "compatible" property and
+* initializing it instead of using the standard DT + device driver
+* model of creating a struct device and then initializing it in the
+* probe function. Please refactor your driver.
+*/
+ if (!fwnode_dev && of_find_property(gdev->dev.of_node, "compatible")) {
+ chip_warn(gc, "Create a real device for %pOF\n" of_node);
+ gdev->dev.fwnode = fwnode;
+ }
#endif
gdev->id = ida_alloc(_ida, GFP_KERNEL);
@@ -4202,6 +4221,17 @@ void gpiod_put_array(struct gpio_descs *descs)
}
EXPORT_SYMBOL_GPL(gpiod_put_array);
+static int gpio_drv_probe(struct device *dev)
+{
+ return 0;
+}
+
+static struct device_driver gpio_drv = {
+ .name = "gpio_drv",
+ .bus = _bus_type,
+ .probe = gpio_drv_probe,
+};
+
static int __init gpiolib_dev_init(void)
{
int ret;
@@ -4213,9 +4243,16 @@ static int __init gpiolib_dev_init(void)
return ret;
}
+ if (driver_register(_drv) < 0) {
+ pr_err("gpiolib: could not register GPIO stub driver\n");
+ bus_unregister(_bus_type);
+ return ret;
+ }
+
ret = alloc_chrdev_region(_devt, 0, GPIO_DEV_MAX, GPIOCHIP_NAME);
if (ret < 0) {
