linux-kernel - Re: [PATCH v2 01/15] nvmem: add support for cell lookups

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Message-ID: <25ebceca-8cdd-edae-6393-dd29eb323c53@linaro.org>
Date:   Tue, 26 Jun 2018 12:06:19 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>, Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Grygorii Strashko <grygorii.strashko@...com>,
        "David S . Miller" <davem@...emloft.net>,
        Lukas Wunner <lukas@...ner.de>, Rob Herring <robh@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        David Lechner <david@...hnology.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Lunn <andrew@...n.ch>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, netdev@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v2 01/15] nvmem: add support for cell lookups

Thanks for the patch,

On 26/06/18 11:22, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> We can currently only register nvmem cells from device tree or by
> manually calling nvmem_add_cells(). The latter options however forces
> users to make sure that the nvmem provider with which the cells are
> associated is registered before the call.
> 
> This patch proposes a new solution inspired by other frameworks that
> offer resource lookups (GPIO, PWM etc.). It adds a function that allows
> machine code to register nvmem lookup which are later lazily used to
> add corresponding nvmem cells.
> 
Overall the idea look fine to me.

This needs to be documented in ./Documentation/nvmem/nvmem.txt

> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> ---
>   drivers/nvmem/core.c           | 57 +++++++++++++++++++++++++++++++++-
>   include/linux/nvmem-consumer.h |  6 ++++
>   include/linux/nvmem-provider.h |  6 ++++
>   3 files changed, 68 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index b5b0cdc21d01..a2e87b464319 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -62,6 +62,9 @@ static DEFINE_IDA(nvmem_ida);
>   static LIST_HEAD(nvmem_cells);
>   static DEFINE_MUTEX(nvmem_cells_mutex);
>   
> +static LIST_HEAD(nvmem_cell_lookups);
> +static DEFINE_MUTEX(nvmem_lookup_mutex);
> +
>   #ifdef CONFIG_DEBUG_LOCK_ALLOC
>   static struct lock_class_key eeprom_lock_key;
>   #endif
> @@ -247,6 +250,23 @@ static const struct attribute_group *nvmem_ro_root_dev_groups[] = {
>   	NULL,
>   };
>   
> +/**
> + * nvmem_register_lookup() - register a number of nvmem cell lookup entries
> + *

Can we rename this to nvmem_add_lookup_table()?
register sound bit heavy here.

We should also have something like nvmem_remove_lookup_table() for 
consistency, and it should ensure that it clears the cells entry too.

> + * @lookup: array of nvmem cell lookup entries
> + * @nentries: number of lookup entries in the array
> + */
> +void nvmem_register_lookup(struct nvmem_cell_lookup *lookup, size_t nentries)
> +{
> +	int i;
> + > +	mutex_lock(&nvmem_lookup_mutex);
> +	for (i = 0; i < nentries; i++)
> +		list_add_tail(&lookup[i].list, &nvmem_cell_lookups);
> +	mutex_unlock(&nvmem_lookup_mutex);
> +}
> +EXPORT_SYMBOL_GPL(nvmem_register_lookup);
> +
>   static void nvmem_release(struct device *dev)
>   {
>   	struct nvmem_device *nvmem = to_nvmem_device(dev);
> @@ -916,6 +936,37 @@ struct nvmem_cell *of_nvmem_cell_get(struct device_node *np,
>   EXPORT_SYMBOL_GPL(of_nvmem_cell_get);
>   #endif
>