From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean Delvare Subject: Re: [RFC] i2c-stub: make it usable with DT when booting Date: Thu, 18 May 2017 10:52:53 +0200 Message-ID: <20170518105253.058a90a6@endymion> References: <20170516112758.2842-1-wsa+renesas@sang-engineering.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170516112758.2842-1-wsa+renesas@sang-engineering.com> Sender: linux-renesas-soc-owner@vger.kernel.org To: Wolfram Sang Cc: linux-i2c@vger.kernel.org, Guenter Roeck , linux-renesas-soc@vger.kernel.org List-Id: linux-i2c@vger.kernel.org Hi Wolfram, On Tue, 16 May 2017 13:27:58 +0200, Wolfram Sang wrote: > This patch makes the stub driver parse the device tree when booting and > create a virtual bus with the desired devices attached. Here is an > example DTS snipplet making use of it. It is for simulating a more > complex camera device which has dependencies which needs to be sorted > out at boot time: > > i2c@42 { > compatible = "i2c-stub"; > > #address-cells = <1>; > #size-cells = <0>; > > des@4c { > compatible = "maxim,max9268"; > reg = <0x4c>; > }; > > eeprom@57 { > compatible = "atmel,24c02"; > reg = <0x57>; > }; > }; I get the idea and I understand the need to emulate the devices early in the boot process. However, how do you deal with the I2C devices pre-initialization (setting initial register values)? This is typically done in user-space with the i2c-stub-from-dump script, or manual calls to i2cset, but that would be too late in your case, wouldn't it? > > FIXME: can fw_* calls be used instead of of_*? > > Signed-off-by: Wolfram Sang > --- > > It was really useful when developing. When using fw_* calls, we probably could > make use of it with ACPI as well. Still, calling for opinions if we want this > upstream or if we want to stay module-only? Also, the binding should really > be marked as "development only". Or is it better to keep it as a separate > patch to keep the binding un-official? Code looks sane, but I can't comment on the bindings side of things as this isn't my area. -- Jean Delvare SUSE L3 Support