linux-kernel - Re: [PATCH v2 13/16] nvmem: add support for cell lookups from machine code

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Date:   Mon, 10 Sep 2018 08:32:30 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>,
        "David S . Miller" <davem@...emloft.net>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>, Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        David Lechner <david@...hnology.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>, Alban Bedel <albeu@...e.fr>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v2 13/16] nvmem: add support for cell lookups from machine
 code



On 07/09/18 11:07, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> Add a way for machine code users to associate devices with nvmem cells.
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> ---
>   drivers/nvmem/core.c          | 143 +++++++++++++++++++++++++++-------
>   include/linux/nvmem-machine.h |  16 ++++
>   2 files changed, 132 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> index da7a9d5beb33..9e2f9c993a07 100644
> --- a/drivers/nvmem/core.c
> +++ b/drivers/nvmem/core.c
> @@ -62,6 +62,9 @@ static DEFINE_IDA(nvmem_ida);
>   static DEFINE_MUTEX(nvmem_cell_mutex);
>   static LIST_HEAD(nvmem_cell_tables);
>   
> +static DEFINE_MUTEX(nvmem_lookup_mutex);
> +static LIST_HEAD(nvmem_lookup_list);
> +
>   static BLOCKING_NOTIFIER_HEAD(nvmem_notifier);
>   
>   #ifdef CONFIG_DEBUG_LOCK_ALLOC
> @@ -285,6 +288,18 @@ static struct nvmem_device *of_nvmem_find(struct device_node *nvmem_np)
>   	return to_nvmem_device(d);
>   }
>   
> +static struct nvmem_device *nvmem_find(const char *name)
> +{
> +	struct device *d;
> +
> +	d = bus_find_device_by_name(&nvmem_bus_type, NULL, name);
> +
> +	if (!d)
> +		return NULL;
> +
> +	return to_nvmem_device(d);
> +}
> +
This is removed and added back in same patch, you should consider 
positioning the caller if possible to avoid any un-necessary changes.

>   static void nvmem_cell_drop(struct nvmem_cell *cell)
>   {
>   	mutex_lock(&nvmem_mutex);
> @@ -421,6 +436,21 @@ nvmem_find_cell_by_index(struct nvmem_device *nvmem, int index)
>   	return cell;
>   }
>   
> +static struct nvmem_cell *
> +nvmem_cell_get_from_lookup(struct device *dev, const char *con_id)
> +{
> +	struct nvmem_cell *cell = ERR_PTR(-ENOENT);
> +	struct nvmem_cell_lookup *lookup;
> +	struct nvmem_device *nvmem;
> +	const char *dev_id;
> +
> +	if (!dev)
> +		return ERR_PTR(-EINVAL);
> +
> +	dev_id = dev_name(dev);
> +
> +	mutex_lock(&nvmem_lookup_mutex);
> +
> +	list_for_each_entry(lookup, &nvmem_lookup_list, node) {
> +		if ((strcmp(lookup->dev_id, dev_id) == 0) &&
> +		    (strcmp(lookup->con_id, con_id) == 0)) {
> +			/* This is the right entry. */
> +			nvmem = __nvmem_device_get(NULL, lookup->nvmem_name);
> +			if (!nvmem) {
> +				/* Provider may not be registered yet. */
> +				cell = ERR_PTR(-EPROBE_DEFER);
> +				goto out;
> +			}
> +
> +			cell = nvmem_find_cell_by_name(nvmem,
> +						       lookup->cell_name);
> +			if (!cell)
> +				goto out;
Here nvmem refcount has already increased, you should probably fix this!
> +		}
> +	}
> +
> +out:
> +	mutex_unlock(&nvmem_lookup_mutex);
> +	return cell;
> +}

...

> diff --git a/include/linux/nvmem-machine.h b/include/linux/nvmem-machine.h

Should be part of nvmem-consumer.h.

> index 1e199dfaacab..7859c08934d5 100644
> --- a/include/linux/nvmem-machine.h
> +++ b/include/linux/nvmem-machine.h
> @@ -26,16 +26,32 @@ struct nvmem_cell_table {
>   	struct list_head	node;
>   };
>   
> +struct nvmem_cell_lookup {
> +	const char		*nvmem_name;
> +	const char		*cell_name;
> +	const char		*dev_id;
> +	const char		*con_id;
> +	struct list_head	node;
> +};

Consider adding kerneldoc to this structure.

> +
>   #if IS_ENABLED(CONFIG_NVMEM)
>   
>   void nvmem_add_cell_table(struct nvmem_cell_table *table);
>   void nvmem_del_cell_table(struct nvmem_cell_table *table);
>   
> +void nvmem_add_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries);
> +void nvmem_del_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries);
> +
>   #else /* CONFIG_NVMEM */
>   
>   static inline void nvmem_add_cell_table(struct nvmem_cell_table *table) {}
>   static inline void nvmem_del_cell_table(struct nvmem_cell_table *table) {}
>   
> +static inline void
> +nvmem_add_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries) {}
> +static inline void
> +nvmem_del_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries) {}
> +
>   #endif /* CONFIG_NVMEM */
>   
>   #endif  /* ifndef _LINUX_NVMEM_MACHINE_H */
>