From: "Benoît Monin" <benoit.monin@bootlin.com>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: "Andi Shyti" <andi.shyti@kernel.org>,
"Rob Herring" <robh@kernel.org>,
"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
"Conor Dooley" <conor+dt@kernel.org>,
"Jarkko Nikula" <jarkko.nikula@linux.intel.com>,
"Mika Westerberg" <mika.westerberg@linux.intel.com>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
"Jan Dabros" <jsd@semihalf.com>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
"Clark Williams" <clrkwllms@kernel.org>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Hans Verkuil" <hverkuil+cisco@kernel.org>,
"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
"Gregory CLEMENT" <gregory.clement@bootlin.com>,
"Théo Lebrun" <theo.lebrun@bootlin.com>,
"Tawfik Bayouk" <tawfik.bayouk@mobileye.com>,
"Vladimir Kondratiev" <vladimir.kondratiev@mobileye.com>,
"Dmitry Guzman" <dmitry.guzman@mobileye.com>,
linux-i2c@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev
Subject: Re: [PATCH 2/3] i2c: designware: Enable transfer with different target addresses
Date: Wed, 22 Oct 2025 10:36:28 +0200 [thread overview]
Message-ID: <5779084.ZASKD2KPVS@benoit.monin> (raw)
In-Reply-To: <aPaS4c-AX0P66T30@shikoro>
On Monday, 20 October 2025 at 21:52:01 CEST, Wolfram Sang wrote:
>
> > For your particular case, that will not help reaching the other segments as
> > we wait for a STOP before changing the target address. So, it should not
> > fail but do a write to segment 0 in your eeprom.
>
> So, this patch replaces a repeated start with a stop + start
> combination? Please don't do this. It will give users a false impression
> that proper repeated start is supported. Honestly reporting that the HW
> does not support is the better option, so the user can decide what to do
> then.
>
This patch replaces a -EINVAL in the middle of the transfer by a
STOP-then-START, but you are right, the expectation is to have a single
STOP at the end of a combined transfer. I somehow overlooked that part.
Maybe I could add support for the I2C_M_STOP flag instead? Or does an
adapter has to support all the protocol mangling if flagged with
I2C_FUNC_PROTOCOL_MANGLING?
That would still allow to group multiple accesses to device that support a
STOP in a transaction when done via i2c_dev I2C_RDWR ioctl, in a single-master
configuration.
Best regards,
--
Benoît Monin, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
next prev parent reply other threads:[~2025-10-22 8:36 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-17 14:59 [PATCH 0/3] i2c: designware: Improve support of multi-messages transfer Benoît Monin
2025-10-17 14:59 ` [PATCH 1/3] dt-bindings: i2c: dw: Add Mobileye I2C controllers Benoît Monin
2025-10-18 15:55 ` Krzysztof Kozlowski
2025-10-17 14:59 ` [PATCH 2/3] i2c: designware: Enable transfer with different target addresses Benoît Monin
2025-10-20 9:38 ` Hans Verkuil
2025-10-20 15:00 ` Benoît Monin
2025-10-20 19:52 ` Wolfram Sang
2025-10-22 8:36 ` Benoît Monin [this message]
2025-10-22 8:58 ` Wolfram Sang
2025-10-17 14:59 ` [PATCH 3/3] i2c: designware: Support of controller with IC_EMPTYFIFO_HOLD_MASTER disabled Benoît Monin
2025-10-18 15:55 ` Krzysztof Kozlowski
2025-10-18 19:57 ` Andy Shevchenko
2025-10-21 15:40 ` Mika Westerberg
2025-10-18 19:49 ` [PATCH 0/3] i2c: designware: Improve support of multi-messages transfer Andy Shevchenko
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