Re: [PATCH] firmware: vpd: Add an interface to read VPD value

From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
To: Stephen Boyd <swboyd@chromium.org>,
	Cheng-yi Chiang <cychiang@chromium.org>
Cc: Guenter Roeck <linux@roeck-us.net>,
	Tzung-Bi Shih <tzungbi@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	ALSA development <alsa-devel@alsa-project.org>,
	Hung-Te Lin <hungte@chromium.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sean Paul <seanpaul@chromium.org>,
	Mark Brown <broonie@kernel.org>, Dylan Reid <dgreid@chromium.org>,
	Tzung-Bi Shih <tzungbi@chromium.org>
Subject: Re: [PATCH] firmware: vpd: Add an interface to read VPD value
Date: Wed, 9 Oct 2019 15:05:12 +0100	[thread overview]
Message-ID: <e968e478-bb48-5b05-b6c4-ae1bf77f714f@linaro.org> (raw)
In-Reply-To: <5d9ca7e4.1c69fb81.7f8fa.3f7d@mx.google.com>

On 08/10/2019 16:14, Stephen Boyd wrote:
>> 3) As my use case does not use device tree, it is hard for ASoC
>> machine to access nvmem device. I am wondering if I can use
>> nvm_cell_lookup so machine driver can find the nvmem device using a
>> con_id. But currently the cell lookup API requires a matched device,
>> which does not fit my usage because there will be different machine
>> drivers requesting the value.
>> I think I can still workaround this by adding the lookup table in
>> machine driver. This would seem to be a bit weird because I found that
>> most lookup table is added in provider side, not consumer side. Not
>> sure if this is logically correct.
> Maybe Srini has some input here. It looks like your main concern is
> consumer to provider mapping?
> 

In non-DT setup, there are various ways to lookup nvmem provider.

1> nvmem_device_get()/put() using provider devid/name. I think you 
should be able to use this in your case.
2> nvmem_register_notifier() which notifies when nvmem provider is added 
to system.
3> nvmem_device_find() with own match function this will be merged in 
next window (https://lkml.org/lkml/2019/10/3/215)

If none of these are of any help, could explain what exactly are you 
looking for w.r.t nvmem to be able to move to what Stephen Boyd suggested?

--srini