Date:	Tue, 16 Jun 2015 15:43:04 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	linux-arm-kernel@...ts.infradead.org
CC:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Rob Herring <robh+dt@...nel.org>,
	Kumar Gala <galak@...eaurora.org>,
	Mark Brown <broonie@...nel.org>, s.hauer@...gutronix.de,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	arnd@...db.de, pantelis.antoniou@...sulko.com, mporter@...sulko.com
Subject: Re: [PATCH v5 03/11] nvmem: Add a simple NVMEM framework for nvmem
 providers

On 05/21/2015 09:43 AM, Srinivas Kandagatla wrote:
>
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> new file mode 100644
> index 0000000..6c2f0b1
> --- /dev/null
> +++ b/drivers/nvmem/core.c
> @@ -0,0 +1,398 @@
> +/*
> + * nvmem framework core.
> + *
> + * Copyright (C) 2015 Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> + * Copyright (C) 2013 Maxime Ripard <maxime.ripard@...e-electrons.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 and
> + * only version 2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/export.h>
> +#include <linux/fs.h>
> +#include <linux/idr.h>
> +#include <linux/init.h>
> +#include <linux/regmap.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>

Is this include used?

> +
> +static int of_nvmem_match(struct device *dev, const void *nvmem_np)
> +{
> +	return dev->of_node == nvmem_np;
> +}
> +
> +static struct nvmem_device *of_nvmem_find(struct device_node *nvmem_np)

const?

> +{
> +	struct device *d;
> +
> +	if (!nvmem_np)
> +		return NULL;
> +
> +	d = class_find_device(&nvmem_class, NULL, nvmem_np, of_nvmem_match);
> +
> +	return d ? to_nvmem_device(d) : NULL;
> +}
> +
> +static struct nvmem_cell *nvmem_find_cell(const char *cell_id)
> +{
> +	struct nvmem_cell *p;
> +
> +	list_for_each_entry(p, &nvmem_cells, node) {

Unnecessary braces.

> +		if (p && !strcmp(p->name, cell_id))
> +			return p;
> +	}
> +
> +	return NULL;
> +}
> +
> +static void nvmem_cell_drop(struct nvmem_cell *cell)
> +{
> +	mutex_lock(&nvmem_cells_mutex);
> +	list_del(&cell->node);
> +	mutex_unlock(&nvmem_cells_mutex);
> +	kfree(cell);
> +}
> +
> +static void nvmem_device_remove_all_cells(struct nvmem_device *nvmem)
> +{
> +	struct nvmem_cell *cell = NULL;

Unnecessary initialization

> +	struct list_head *p, *n;
> +
> +	list_for_each_safe(p, n, &nvmem_cells) {
> +		cell = list_entry(p, struct nvmem_cell, node);
> +		if (cell->nvmem == nvmem)
> +			nvmem_cell_drop(cell);
> +	}
[..]
> +
> +static int nvmem_add_cells(struct nvmem_device *nvmem,
> +			   struct nvmem_config *cfg)
> +{
> +	struct nvmem_cell **cells;
> +	struct nvmem_cell_info *info = cfg->cells;
> +	int i, rval;
> +
> +	cells = kzalloc(sizeof(*cells) * cfg->ncells, GFP_KERNEL);

kcalloc

> +	if (!cells)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < cfg->ncells; i++) {
> +		cells[i] = kzalloc(sizeof(struct nvmem_cell), GFP_KERNEL);

sizeof(**cells) ?

> +		if (!cells[i]) {
> +			rval = -ENOMEM;
> +			goto err;
> +		}
> +
> +		rval = nvmem_cell_info_to_nvmem_cell(nvmem, &info[i], cells[i]);
> +		if (IS_ERR_VALUE(rval)) {
> +			kfree(cells[i]);
> +			goto err;
> +		}
> +
> +		nvmem_cell_add(cells[i]);
> +	}
> +
> +	nvmem->ncells = cfg->ncells;
> +	/* remove tmp array */
> +	kfree(cells);
> +
> +	return 0;
> +err:
> +	while (--i)
> +		nvmem_cell_drop(cells[i]);
> +
> +	return rval;
> +}
> +
> +/**
> + * nvmem_register(): Register a nvmem device for given nvmem.
> + * Also creates an binary entry in /sys/class/nvmem/dev-name/nvmem
> + *
> + * @nvmem: nvmem device that needs to be created

You mean @config?

> + *
> + * The return value will be an ERR_PTR() on error or a valid pointer
> + * to nvmem_device.
> + */
> +
> +struct nvmem_device *nvmem_register(struct nvmem_config *config)
> +{
> +	struct nvmem_device *nvmem;
> +	struct regmap *rm;
> +	int rval;
> +
> +	if (!config->dev)
> +		return ERR_PTR(-EINVAL);
> +
> +	rm = dev_get_regmap(config->dev, NULL);
> +	if (!rm) {
> +		dev_err(config->dev, "Regmap not found\n");
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	nvmem = kzalloc(sizeof(*nvmem), GFP_KERNEL);
> +	if (!nvmem)
> +		return ERR_PTR(-ENOMEM);
> +
> +	nvmem->id = ida_simple_get(&nvmem_ida, 0, 0, GFP_KERNEL);
> +	if (nvmem->id < 0) {
> +		kfree(nvmem);
> +		return ERR_PTR(nvmem->id);
> +	}
> +
> +	nvmem->regmap = rm;
> +	nvmem->owner = config->owner;
> +	nvmem->stride = regmap_get_reg_stride(rm);
> +	nvmem->word_size = regmap_get_val_bytes(rm);
> +	nvmem->size = regmap_get_max_register(rm) + nvmem->stride;
> +	nvmem->dev.class = &nvmem_class;
> +	nvmem->dev.parent = config->dev;
> +	nvmem->dev.of_node = config->dev->of_node;
> +	dev_set_name(&nvmem->dev, "%s%d",
> +		     config->name ? : "nvmem", config->id);

It may be better to always name it nvmem%d so that we don't allow the
possibility of conflicts.

> +
> +	nvmem->read_only = of_property_read_bool(nvmem->dev.of_node,
> +						 "read-only");

What if we're not using DT? How would we specify read_only?

> +
> +	device_initialize(&nvmem->dev);
> +
> +	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n",
> +		dev_name(&nvmem->dev));
> +
> +	rval = device_add(&nvmem->dev);
> +	if (rval) {
> +		ida_simple_remove(&nvmem_ida, nvmem->id);
> +		kfree(nvmem);
> +		return ERR_PTR(rval);
> +	}
> +
> +	/* update sysfs attributes */
> +	if (nvmem->read_only)
> +		sysfs_update_group(&nvmem->dev.kobj, &nvmem_bin_ro_group);

It would be nice if this could be done before the device was registered.
Perhaps have two device_types, one for read-only and one for read/write?

> +
> +	if (config->cells)
> +		nvmem_add_cells(nvmem, config);
> +
> +	return nvmem;
> +}
> +EXPORT_SYMBOL_GPL(nvmem_register);
> +
> +/**
> + * nvmem_unregister(): Unregister previously registered nvmem device
> + *
> + * @nvmem: Pointer to previously registered nvmem device.
> + *
> + * The return value will be an non zero on error or a zero on success.
> + */
> +int nvmem_unregister(struct nvmem_device *nvmem)
> +{
> +	mutex_lock(&nvmem_mutex);
> +	if (nvmem->users) {
> +		mutex_unlock(&nvmem_mutex);
> +		return -EBUSY;

Hmm... that doesn't seem nice. Typically when something is unregistered
we have to pull the rug out from underneath the users and start
returning errors to them. The provider needs to be free to unregister
because it's been forcibly removed. So really this function should
return void.

> +	}
> +	mutex_unlock(&nvmem_mutex);
> +
> +	nvmem_device_remove_all_cells(nvmem);
> +	device_del(&nvmem->dev);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(nvmem_unregister);
> +
> +static int nvmem_init(void)

__init? And __exit on nvmem_exit?

> +{
> +	return class_register(&nvmem_class);

I thought class was on the way out? Aren't we supposed to use bus types
for new stuff?

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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