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From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
To: Bartosz Golaszewski <brgl@bgdev.pl>,
	Boris Brezillon <boris.brezillon@bootlin.com>
Cc: Andrew Lunn <andrew@lunn.ch>,
	linux-doc <linux-doc@vger.kernel.org>,
	Sekhar Nori <nsekhar@ti.com>,
	Bartosz Golaszewski <bgolaszewski@baylibre.com>,
	linux-i2c <linux-i2c@vger.kernel.org>,
	Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
	Rob Herring <robh@kernel.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Kevin Hilman <khilman@kernel.org>,
	Richard Weinberger <richard@nod.at>,
	Russell King <linux@armlinux.org.uk>,
	Marek Vasut <marek.vasut@gmail.com>,
	Paolo Abeni <pabeni@redhat.com>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Grygorii Strashko <grygorii.strashko@ti.com>,
	David Lechner <david@lechnology.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Sven Van Asbroeck <svendev@arcx.com>,
	"open list:MEMORY TECHNOLOGY..." <linux-mtd@lists.infradead.org>,
	Linux-OMAP <linux-omap@vger.kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Lukas Wunner <lukas@wunner.de>, Naren <naren.kernel@gmail.com>,
	netdev <netdev@vger.kernel.org>, Alban Bedel <albeu@free.fr>,
	Andrew Morton <akpm@linux-foundation.org>,
	Brian Norris <computersforpeace@gmail.com>,
	David Woodhouse <dwmw2@infradead.org>,
	"David S . Miller" <davem@davemloft.net>
Subject: Re: [PATCH v2 01/29] nvmem: add support for cell lookups
Date: Tue, 28 Aug 2018 11:15:12 +0100
Message-ID: <8cb75723-dc87-f127-2aab-54dd0b08eee8@linaro.org> (raw)
In-Reply-To: <CAMRc=MfpZJUEAhM4OoLbmJcnX3rTJk8fvdiL6=9BjNkVcsf=SA@mail.gmail.com>


On 27/08/18 14:37, Bartosz Golaszewski wrote:
> I didn't notice it before but there's a global list of nvmem cells

Bit of history here.

The global list of nvmem_cell is to assist non device tree based cell 
lookups. These cell entries come as part of the non-dt providers 
nvmem_config.

All the device tree based cell lookup happen dynamically on 
request/demand, and all the cell definition comes from DT.

As of today NVMEM supports both DT and non DT usecase, this is much simpler.

Non dt cases have various consumer usecases.

1> Consumer is aware of provider name and cell details.
	This is probably simple usecase where it can just use device based apis.

2> Consumer is not aware of provider name, its just aware of cell name.
	This is the case where global list of cells are used.

> with each cell referencing its owner nvmem device. I'm wondering if
> this isn't some kind of inversion of ownership. Shouldn't each nvmem
> device have a separate list of nvmem cells owned by it? What happens
This is mainly done for use case where consumer does not have idea of 
provider name or any details.

First thing non dt user should do is use "NVMEM device based consumer APIs"

ex: First get handle to nvmem device using its nvmem provider name by 
calling nvmem_device_get(); and use nvmem_device_cell_read/write() apis.

Also am not 100% sure how would maintaining cells list per nvmem 
provider would help for the intended purpose of global list?

> if we have two nvmem providers with the same names for cells? I'm
Yes, it would return the first instance.. which is a known issue.
Am not really sure this is a big problem as of today! but am open for 
any better suggestions!


> asking because dev_id based lookup doesn't make sense if internally
> nvmem_cell_get_from_list() doesn't care about any device names (takes
> only the cell_id as argument).

As I said this is for non DT usecase where consumers are not aware of 
provider details.

> 
> This doesn't cause any trouble now since there are no users defining
> cells in nvmem_config - there are only DT users - but this must be
> clarified before I can advance with correctly implementing nvmem
> lookups.
DT users should not be defining this to start with! It's redundant and 
does not make sense!

> 
> BTW: of_nvmem_cell_get() seems to always allocate an nvmem_cell
> instance even if the cell for this node was already added to the nvmem
> device.
I hope you got the reason why of_nvmem_cell_get() always allocates new 
instance for every get!!

thanks,
srini

  parent reply index

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-10  8:04 [PATCH v2 00/29] at24: remove at24_platform_data Bartosz Golaszewski
2018-08-10  8:04 ` [PATCH v2 01/29] nvmem: add support for cell lookups Bartosz Golaszewski
2018-08-24 15:08   ` Boris Brezillon
2018-08-24 15:27     ` Andrew Lunn
2018-08-25  6:27       ` Boris Brezillon
2018-08-27  8:56         ` Bartosz Golaszewski
2018-08-27  9:00           ` Boris Brezillon
2018-08-27 13:37             ` Bartosz Golaszewski
2018-08-27 14:01               ` Boris Brezillon
2018-08-28 10:15               ` Srinivas Kandagatla [this message]
2018-08-28 11:56                 ` Bartosz Golaszewski
2018-08-28 13:45                   ` Srinivas Kandagatla
2018-08-28 14:41                     ` Bartosz Golaszewski
2018-08-28 14:48                       ` Srinivas Kandagatla
2018-08-28 14:53                       ` Boris Brezillon
2018-08-28 15:09                         ` Srinivas Kandagatla
2018-08-10  8:04 ` [PATCH v2 02/29] Documentation: nvmem: document lookup entries Bartosz Golaszewski
2018-08-31 20:30   ` Brian Norris
2018-09-01 13:11     ` Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 03/29] nvmem: add a notifier chain Bartosz Golaszewski
2018-08-10  8:33   ` Srinivas Kandagatla
2018-08-10  8:05 ` [PATCH v2 04/29] nvmem: provide nvmem_dev_name() Bartosz Golaszewski
2018-08-10  8:10   ` Srinivas Kandagatla
2018-08-10  8:05 ` [PATCH v2 05/29] nvmem: remove the name field from struct nvmem_device Bartosz Golaszewski
2018-08-10  8:33   ` Srinivas Kandagatla
2018-08-10  8:05 ` [PATCH v2 06/29] mtd: Add support for reading MTD devices via the nvmem API Bartosz Golaszewski
2018-08-17 16:27   ` Boris Brezillon
2018-08-19 11:31     ` Alban
2018-08-19 16:46       ` Boris Brezillon
2018-08-20 10:43         ` Srinivas Kandagatla
2018-08-20 18:20           ` Boris Brezillon
2018-08-20 18:50             ` Bartosz Golaszewski
2018-08-20 19:06               ` Boris Brezillon
2018-08-20 21:27             ` Alban
2018-08-21  5:07               ` Boris Brezillon
2018-08-21  9:50             ` Srinivas Kandagatla
2018-08-21  9:56               ` Boris Brezillon
2018-08-21 10:11                 ` Srinivas Kandagatla
2018-08-21 10:43                   ` Boris Brezillon
2018-08-21 11:39               ` Alban
2018-08-21 12:00                 ` Srinivas Kandagatla
2018-08-21 13:01                   ` Boris Brezillon
2018-08-23 10:29                     ` Alban
2018-08-24 14:39                       ` Boris Brezillon
2018-08-28 10:20                       ` Srinivas Kandagatla
2018-08-20 22:53         ` Alban
2018-08-21  5:44           ` Boris Brezillon
2018-08-21  9:38             ` Srinivas Kandagatla
2018-08-21 11:31               ` Boris Brezillon
2018-08-21 13:34                 ` Srinivas Kandagatla
2018-08-21 13:37                   ` Srinivas Kandagatla
2018-08-21 13:57                     ` Boris Brezillon
2018-08-21 12:27             ` Alban
2018-08-21 12:57               ` Boris Brezillon
2018-08-21 13:57                 ` Alban
2018-08-21 14:26                   ` Boris Brezillon
2018-08-21 14:33                     ` Srinivas Kandagatla
2018-08-10  8:05 ` [PATCH v2 07/29] ARM: davinci: dm365-evm: use nvmem lookup for mac address Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 08/29] ARM: davinci: dm644-evm: " Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 09/29] ARM: davinci: dm646x-evm: " Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 10/29] ARM: davinci: da830-evm: " Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 11/29] ARM: davinci: mityomapl138: add nvmem cells lookup entries Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 12/29] ARM: davinci: da850-evm: use nvmem lookup for mac address Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 13/29] ARM: davinci: da850-evm: remove unnecessary include Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 14/29] net: simplify eth_platform_get_mac_address() Bartosz Golaszewski
2018-08-10 14:39   ` Andy Shevchenko
2018-08-10 16:17     ` Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 15/29] net: split eth_platform_get_mac_address() into subroutines Bartosz Golaszewski
2018-08-31 19:54   ` Brian Norris
2018-08-10  8:05 ` [PATCH v2 16/29] net: add support for nvmem to eth_platform_get_mac_address() Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 17/29] net: davinci_emac: use eth_platform_get_mac_address() Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 18/29] ARM: davinci: da850-evm: remove dead MTD code Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 19/29] ARM: davinci: mityomapl138: don't read the MAC address from machine code Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 20/29] ARM: davinci: dm365-evm: use device properties for at24 eeprom Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 21/29] ARM: davinci: da830-evm: " Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 22/29] ARM: davinci: dm644x-evm: " Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 23/29] ARM: davinci: dm646x-evm: " Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 24/29] ARM: davinci: sffsdr: fix the at24 eeprom device name Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 25/29] ARM: davinci: sffsdr: use device properties for at24 eeprom Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 26/29] ARM: davinci: remove dead code related to MAC address reading Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 27/29] ARM: davinci: mityomapl138: use nvmem notifiers Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 28/29] ARM: davinci: mityomapl138: use device properties for at24 eeprom Bartosz Golaszewski
2018-08-10  8:05 ` [PATCH v2 29/29] eeprom: at24: kill at24_platform_data Bartosz Golaszewski
2018-08-10  8:41 ` [PATCH v2 00/29] at24: remove at24_platform_data Srinivas Kandagatla
2018-08-31 19:46 ` Brian Norris
2018-10-03 20:15   ` Bartosz Golaszewski
2018-10-03 20:30     ` Lukas Wunner
2018-10-03 21:04     ` Florian Fainelli
2018-10-04 11:06       ` Bartosz Golaszewski
2018-10-04 13:58         ` Arnd Bergmann
2018-10-04 14:35           ` Sowmini Varadhan
2018-10-04 14:38             ` Arnd Bergmann

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