linux-kernel - Re: [PATCH v4 3/9] nvmem: core: add nvmem_device

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Date:   Wed, 14 Aug 2019 13:52:49 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Thomas Bogendoerfer <tbogendoerfer@...e.de>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Evgeniy Polyakov <zbr@...emap.net>, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        netdev@...r.kernel.org, linux-rtc@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH v4 3/9] nvmem: core: add nvmem_device_find



On 14/08/2019 12:46, Thomas Bogendoerfer wrote:
> On Tue, 13 Aug 2019 10:40:34 +0100
> Srinivas Kandagatla <srinivas.kandagatla@...aro.org> wrote:
> 
>>
>>
>> On 09/08/2019 11:32, Thomas Bogendoerfer wrote:
>>> nvmem_device_find provides a way to search for nvmem devices with
>>> the help of a match function simlair to bus_find_device.
>>>
>>> Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@...e.de>
>>> ---
>>>    drivers/nvmem/core.c           | 62 ++++++++++++++++++++++--------------------
>>>    include/linux/nvmem-consumer.h |  9 ++++++
>>>    2 files changed, 41 insertions(+), 30 deletions(-)
>>
>> Have you considered using nvmem_register_notifier() ?
> 
> yes, that was the first idea. But then I realized I need to build up
> a private database of information already present in nvmem bus. So I
> looked for a way to retrieve it from there. Unfortunately I couldn't
> use bus_find_device directly, because nvmem_bus_type and struct nvmem_device
> is hidden. So I refactured the lookup code and added a more universal
> lookup function, which fits my needs and should be usable for more.
I see your point.

overall the patch as it is look good, but recently we added more generic 
lookups for DT node, looks like part of your patch is un-doing generic 
device name lookup.

DT node match lookup is in 
https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git/log/?h=generic_lookup_helpers

of_nvmem_match and nvmem_match_name are duplicating the code here.
Looks like its possible to use generic lookups along with custom match 
by splitting __nvmem_device_get() to two functions, one for lookup and 
other for refcounting.

Other missing bit is adding this api to documentation in 
./Documentation/driver-api/nvmem.rst


thanks,
srini
> 
> Thomas.
>