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Date: Wed, 9 Jun 2021 17:51:15 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: William Breathitt Gray <vilhelm.gray@...il.com>
Cc: Jonathan.Cameron@...wei.com,
linux-stm32@...md-mailman.stormreply.com, kernel@...gutronix.de,
linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESEND PATCH v11 22/33] counter: Internalize sysfs interface
code
On Wed, 9 Jun 2021 23:11:45 +0900
William Breathitt Gray <vilhelm.gray@...il.com> wrote:
> This is a reimplementation of the Generic Counter driver interface.
> There are no modifications to the Counter subsystem userspace interface,
> so existing userspace applications should continue to run seamlessly.
>
> The purpose of this patch is to internalize the sysfs interface code
> among the various counter drivers into a shared module. Counter drivers
> pass and take data natively (i.e. u8, u64, etc.) and the shared counter
> module handles the translation between the sysfs interface and the
> device drivers. This guarantees a standard userspace interface for all
> counter drivers, and helps generalize the Generic Counter driver ABI in
> order to support the Generic Counter chrdev interface (introduced in a
> subsequent patch) without significant changes to the existing counter
> drivers.
>
> Note, Counter device registration is the same as before: drivers
> populate a struct counter_device with components and callbacks, then
> pass the structure to the devm_counter_register function. However,
> what's different now is how the Counter subsystem code handles this
> registration internally.
>
> Whereas before callbacks would interact directly with sysfs data, this
> interaction is now abstracted and instead callbacks interact with native
> C data types. The counter_comp structure forms the basis for Counter
> extensions.
>
> The counter-sysfs.c file contains the code to parse through the
> counter_device structure and register the requested components and
> extensions. Attributes are created and populated based on type, with
> respective translation functions to handle the mapping between sysfs and
> the counter driver callbacks.
>
> The translation performed for each attribute is straightforward: the
> attribute type and data is parsed from the counter_attribute structure,
> the respective counter driver read/write callback is called, and sysfs
> I/O is handled before or after the driver read/write function is called.
>
> Cc: Syed Nayyar Waris <syednwaris@...il.com>
> Cc: Jarkko Nikula <jarkko.nikula@...ux.intel.com>
> Cc: Patrick Havelange <patrick.havelange@...ensium.com>
> Cc: Kamel Bouhara <kamel.bouhara@...tlin.com>
> Cc: Fabrice Gasnier <fabrice.gasnier@...com>
> Cc: Maxime Coquelin <mcoquelin.stm32@...il.com>
> Cc: Alexandre Torgue <alexandre.torgue@...com>
> Cc: Dan Carpenter <dan.carpenter@...cle.com>
> Reviewed-by: David Lechner <david@...hnology.com>
> Tested-by: David Lechner <david@...hnology.com>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@...il.com>
Given you will probably do a v12 anyway, a few comments inline.
Jonathan
> ---
> MAINTAINERS | 1 -
> drivers/counter/104-quad-8.c | 449 +++----
> drivers/counter/Makefile | 1 +
> drivers/counter/counter-core.c | 155 +++
> drivers/counter/counter-sysfs.c | 846 +++++++++++++
> drivers/counter/counter-sysfs.h | 13 +
> drivers/counter/counter.c | 1496 -----------------------
> drivers/counter/ftm-quaddec.c | 56 +-
> drivers/counter/intel-qep.c | 144 +--
> drivers/counter/interrupt-cnt.c | 62 +-
> drivers/counter/microchip-tcb-capture.c | 93 +-
> drivers/counter/stm32-lptimer-cnt.c | 162 ++-
> drivers/counter/stm32-timer-cnt.c | 147 +--
> drivers/counter/ti-eqep.c | 180 +--
> include/linux/counter.h | 629 +++++-----
> include/linux/counter_enum.h | 45 -
> 16 files changed, 1918 insertions(+), 2561 deletions(-)
> create mode 100644 drivers/counter/counter-core.c
> create mode 100644 drivers/counter/counter-sysfs.c
> create mode 100644 drivers/counter/counter-sysfs.h
> delete mode 100644 drivers/counter/counter.c
> delete mode 100644 include/linux/counter_enum.h
>
...
> diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c
> new file mode 100644
> index 000000000000..e7dd6ea01c8a
> --- /dev/null
> +++ b/drivers/counter/counter-core.c
> @@ -0,0 +1,155 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Generic Counter interface
> + * Copyright (C) 2020 William Breathitt Gray
> + */
> +#include <linux/counter.h>
> +#include <linux/device.h>
> +#include <linux/export.h>
> +#include <linux/gfp.h>
> +#include <linux/idr.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +
> +#include "counter-sysfs.h"
> +
> +/* Provides a unique ID for each counter device */
> +static DEFINE_IDA(counter_ida);
> +
...
> +int counter_register(struct counter_device *const counter)
> +{
> + struct device *const dev = &counter->dev;
> + int id;
> + int err;
> +
> + /* Acquire unique ID */
> + id = ida_alloc(&counter_ida, GFP_KERNEL);
> + if (id < 0)
> + return id;
> +
> + /* Configure device structure for Counter */
> + dev->id = id;
> + dev->type = &counter_device_type;
> + dev->bus = &counter_bus_type;
> + if (counter->parent) {
> + dev->parent = counter->parent;
> + dev->of_node = counter->parent->of_node;
> + }
> + device_initialize(dev);
> + dev_set_drvdata(dev, counter);
> +
> + /* Add Counter sysfs attributes */
> + err = counter_sysfs_add(counter);
> + if (err < 0)
> + goto err_free_id;
> +
> + /* Add device to system */
> + err = device_add(dev);
> + if (err < 0)
> + goto err_free_id;
> +
> + return 0;
> +
> +err_free_id:
> + put_device(dev);
> + return err;
> +}
> +EXPORT_SYMBOL_GPL(counter_register);
> +
> +/**
> + * counter_unregister - unregister Counter from the system
> + * @counter: pointer to Counter to unregister
> + *
> + * The Counter is unregistered from the system; all allocated memory is freed.
If we are being fussy. This isn't necessarily true. If the reference goes
down to 0 it will be freed, but in theory that could happen later than
this call. I'm guessing we will have get_device() calls once the
chrdev is in place.
> + */
> +void counter_unregister(struct counter_device *const counter)
> +{
> + if (!counter)
> + return;
> +
> + device_unregister(&counter->dev);
> +}
> +EXPORT_SYMBOL_GPL(counter_unregister);
> +
> +static void devm_counter_release(struct device *dev, void *res)
> +{
> + counter_unregister(*(struct counter_device **)res);
> +}
> +
> +/**
> + * devm_counter_register - Resource-managed counter_register
> + * @dev: device to allocate counter_device for
> + * @counter: pointer to Counter to register
> + *
> + * Managed counter_register. The Counter registered with this function is
> + * automatically unregistered on driver detach. This function calls
> + * counter_register internally. Refer to that function for more information.
> + *
> + * RETURNS:
> + * 0 on success, negative error number on failure.
> + */
> +int devm_counter_register(struct device *dev,
> + struct counter_device *const counter)
> +{
> + struct counter_device **ptr;
> + int err;
> +
> + ptr = devres_alloc(devm_counter_release, sizeof(*ptr), GFP_KERNEL);
> + if (!ptr)
> + return -ENOMEM;
If you look at how devm_iio_device_register() is now done in
the togreg branch of iio.git, you'll see it now just uses
devm_add_action_or_reset() internally. I think you could do something similar
here and reduce boilerplate a little.
> +
> + err = counter_register(counter);
> + if (err < 0) {
> + devres_free(ptr);
> + return err;
> + }
> +
> + *ptr = counter;
> + devres_add(dev, ptr);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(devm_counter_register);
> +
> +static int __init counter_init(void)
> +{
> + return bus_register(&counter_bus_type);
> +}
> +
> +static void __exit counter_exit(void)
> +{
> + bus_unregister(&counter_bus_type);
> +}
> +
> +subsys_initcall(counter_init);
> +module_exit(counter_exit);
> +
> +MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@...il.com>");
> +MODULE_DESCRIPTION("Generic Counter interface");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/counter/counter-sysfs.c b/drivers/counter/counter-sysfs.c
> new file mode 100644
> index 000000000000..07588130600a
> --- /dev/null
> +++ b/drivers/counter/counter-sysfs.c
> @@ -0,0 +1,846 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Generic Counter sysfs interface
> + * Copyright (C) 2020 William Breathitt Gray
> + */
> +#include <linux/counter.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/gfp.h>
> +#include <linux/kernel.h>
> +#include <linux/list.h>
> +#include <linux/string.h>
> +#include <linux/sysfs.h>
> +#include <linux/types.h>
> +
> +#include "counter-sysfs.h"
> +
...
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