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SubjectRe: [PATCH v8 17/22] counter: Add character device interface
On Sun, Feb 14, 2021 at 06:06:12PM +0000, Jonathan Cameron wrote:
> On Fri, 12 Feb 2021 21:13:41 +0900
> William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
>
> > This patch introduces a character device interface for the Counter
> > subsystem. Device data is exposed through standard character device read
> > operations. Device data is gathered when a Counter event is pushed by
> > the respective Counter device driver. Configuration is handled via ioctl
> > operations on the respective Counter character device node.
> >
> > Cc: David Lechner <david@lechnology.com>
> > Cc: Gwendal Grignou <gwendal@chromium.org>
> > Cc: Dan Carpenter <dan.carpenter@oracle.com>
> > Cc: Oleksij Rempel <o.rempel@pengutronix.de>
> > Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>
> Hi William,
>
> A few minor comments. Mostly seems to have come together well and
> makes sense to me.
>
> Jonathan
>
> > ---
> > drivers/counter/Makefile | 2 +-
> > drivers/counter/counter-chrdev.c | 496 +++++++++++++++++++++++++++++++
> > drivers/counter/counter-chrdev.h | 16 +
> > drivers/counter/counter-core.c | 37 ++-
> > include/linux/counter.h | 45 +++
> > include/uapi/linux/counter.h | 70 +++++
> > 6 files changed, 661 insertions(+), 5 deletions(-)
> > create mode 100644 drivers/counter/counter-chrdev.c
> > create mode 100644 drivers/counter/counter-chrdev.h
> >
>
> ...
>
> > diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c
> > index bcf672e1fc0d..c137fcb97d9c 100644
> > --- a/drivers/counter/counter-core.c
> > +++ b/drivers/counter/counter-core.c
> > @@ -5,12 +5,16 @@
> > */
> > #include <linux/counter.h>
> > #include <linux/device.h>
> > +#include <linux/device/bus.h>
> > #include <linux/export.h>
> > +#include <linux/fs.h>
> > #include <linux/gfp.h>
> > #include <linux/idr.h>
> > #include <linux/init.h>
> > #include <linux/module.h>
> > +#include <linux/types.h>
> >
> > +#include "counter-chrdev.h"
> > #include "counter-sysfs.h"
> >
> > /* Provides a unique ID for each counter device */
> > @@ -33,6 +37,8 @@ static struct bus_type counter_bus_type = {
> > .name = "counter"
> > };
> >
> > +static dev_t counter_devt;
> > +
> > /**
> > * counter_register - register Counter to the system
> > * @counter: pointer to Counter to register
> > @@ -54,7 +60,6 @@ int counter_register(struct counter_device *const counter)
> > if (counter->id < 0)
> > return counter->id;
> >
> > - /* Configure device structure for Counter */
>
> Not sure why this comment gets removed here.

This comment wasn't suppose to be removed. I'll revert this.

> > dev->type = &counter_device_type;
> > dev->bus = &counter_bus_type;
> > if (counter->parent) {
> > @@ -65,18 +70,25 @@ int counter_register(struct counter_device *const counter)
> > device_initialize(dev);
> > dev_set_drvdata(dev, counter);
> >
> > + /* Add Counter character device */
> > + err = counter_chrdev_add(counter, counter_devt);
> > + if (err < 0)
> > + goto err_free_id;
> > +
> > /* Add Counter sysfs attributes */
> > err = counter_sysfs_add(counter);
> > if (err < 0)
> > - goto err_free_id;
> > + goto err_remove_chrdev;
> >
> > /* Add device to system */
> > err = device_add(dev);
> > if (err < 0)
> > - goto err_free_id;
> > + goto err_remove_chrdev;
>
> It might be worth thinking about using cdev_device_add()
> though will require a slightly different order of adding.

I think using cdev_device_add() should be possible. I'll adjust
counter_chrdev_add() accordingly to account for this.

> >
> > return 0;
> >
> > +err_remove_chrdev:
> > + counter_chrdev_remove(counter);
> > err_free_id:
> > put_device(dev);
> > return err;
> > @@ -138,13 +150,30 @@ int devm_counter_register(struct device *dev,
> > }
> > EXPORT_SYMBOL_GPL(devm_counter_register);
> >
> > +#define COUNTER_DEV_MAX 256
> > +
> > static int __init counter_init(void)
> > {
> > - return bus_register(&counter_bus_type);
> > + int err;
> > +
> > + err = bus_register(&counter_bus_type);
> > + if (err < 0)
> > + return err;
> > +
> > + err = alloc_chrdev_region(&counter_devt, 0, COUNTER_DEV_MAX, "counter");
> > + if (err < 0)
> > + goto err_unregister_bus;
> > +
> > + return 0;
> > +
> > +err_unregister_bus:
> > + bus_unregister(&counter_bus_type);
> > + return err;
> > }
> >
> > static void __exit counter_exit(void)
> > {
> > + unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
> > bus_unregister(&counter_bus_type);
> > }
> >
>
> ...
>
> > diff --git a/include/uapi/linux/counter.h b/include/uapi/linux/counter.h
> > index 6113938a6044..3d647a5383b8 100644
> > --- a/include/uapi/linux/counter.h
> > +++ b/include/uapi/linux/counter.h
> > @@ -6,6 +6,19 @@
> > #ifndef _UAPI_COUNTER_H_
> > #define _UAPI_COUNTER_H_
> >
> > +#include <linux/ioctl.h>
> > +#include <linux/types.h>
> > +
> > +/* Component type definitions */
> > +enum counter_component_type {
> > + COUNTER_COMPONENT_NONE,
> > + COUNTER_COMPONENT_SIGNAL,
> > + COUNTER_COMPONENT_COUNT,
> > + COUNTER_COMPONENT_FUNCTION,
> > + COUNTER_COMPONENT_SYNAPSE_ACTION,
> > + COUNTER_COMPONENT_EXTENSION,
> > +};
> > +
> > /* Component scope definitions */
> > enum counter_scope {
> > COUNTER_SCOPE_DEVICE,
> > @@ -13,6 +26,63 @@ enum counter_scope {
> > COUNTER_SCOPE_COUNT,
> > };
> >
> > +/**
> > + * struct counter_component - Counter component identification
> > + * @type: component type (one of enum counter_component_type)
> > + * @scope: component scope (one of enum counter_scope)
> > + * @parent: parent component ID (matching the Y/Z suffix of the respective sysfs
> > + * path as described in Documentation/ABI/testing/sysfs-bus-counter)
>
> Probably good to give an example here as well as the cross reference.

Ack.

William Breathitt Gray
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