From: Wolfram Sang <wsa@the-dreams.de>
To: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Akinobu Mita <akinobu.mita@gmail.com>,
linux-media@vger.kernel.org, devicetree@vger.kernel.org,
Jacopo Mondi <jacopo+renesas@jmondi.org>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Hans Verkuil <hans.verkuil@cisco.com>,
Sakari Ailus <sakari.ailus@linux.intel.com>,
Mauro Carvalho Chehab <mchehab@s-opensource.com>
Subject: Re: [PATCH v5 03/14] media: ov772x: allow i2c controllers without I2C_FUNC_PROTOCOL_MANGLING
Date: Tue, 29 May 2018 15:29:29 +0200 [thread overview]
Message-ID: <20180529132929.zthorwdp2axxogvd@ninjato> (raw)
In-Reply-To: <20180529095657.675a6f54@vento.lan>
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> It is a very bad idea to replace an i2c xfer by a pair of i2c
> send()/recv(), as, if are there any other device at the bus managed
> by an independent driver, you may end by mangling i2c transfers and
> eventually cause device malfunctions.
For I2C, this is true and a very important detail. Yet, we are talking
not I2C but SCCB here and SCCB demands a STOP between messages. So,
technically, to avoid what you describe one shouldn't mix I2C and SCCB
devices. I am quite aware the reality is very different, but still...
My preference would be to stop acting as SCCB was I2C but give it its
own set of functions so it becomes clear for everyone what protocol is
used for what device.
> So, IMO, the best is to push the patch you proposed that adds a
> new I2C flag:
>
> https://patchwork.linuxtv.org/patch/49396/
Sorry, but I don't like it. This makes the I2C core code very
unreadable. This is why I think SCCB should be exported to its own
realm. Which may live in i2c-core-sccb.c, no need for a seperate
subsystem.
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next prev parent reply other threads:[~2018-05-29 13:29 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-06 14:19 [PATCH v5 00/14] media: ov772x: support media controller, device tree probing, etc Akinobu Mita
2018-05-06 14:19 ` [PATCH v5 01/14] media: dt-bindings: ov772x: add device tree binding Akinobu Mita
2018-05-06 14:19 ` [PATCH v5 02/14] media: ov772x: correct setting of banding filter Akinobu Mita
2018-05-06 14:19 ` [PATCH v5 03/14] media: ov772x: allow i2c controllers without I2C_FUNC_PROTOCOL_MANGLING Akinobu Mita
2018-05-29 12:59 ` Mauro Carvalho Chehab
2018-05-29 13:29 ` Wolfram Sang [this message]
2018-05-29 14:32 ` Mauro Carvalho Chehab
2018-05-06 14:19 ` [PATCH v5 04/14] media: ov772x: add checks for register read errors Akinobu Mita
2018-05-06 14:19 ` [PATCH v5 05/14] media: ov772x: add media controller support Akinobu Mita
2018-05-06 14:19 ` [PATCH v5 06/14] media: ov772x: use generic names for reset and powerdown gpios Akinobu Mita
2018-05-06 14:19 ` [PATCH v5 07/14] media: ov772x: omit consumer ID when getting clock reference Akinobu Mita
2018-05-06 14:19 ` [PATCH v5 08/14] media: ov772x: support device tree probing Akinobu Mita
2018-05-07 9:26 ` Sakari Ailus
2018-05-07 14:52 ` Akinobu Mita
2018-05-14 9:16 ` jacopo mondi
2018-05-14 11:21 ` Sakari Ailus
2018-05-06 14:19 ` [PATCH v5 09/14] media: ov772x: handle nested s_power() calls Akinobu Mita
2018-05-06 14:19 ` [PATCH v5 10/14] media: ov772x: reconstruct s_frame_interval() Akinobu Mita
2018-05-14 9:02 ` jacopo mondi
2018-05-06 14:19 ` [PATCH v5 11/14] media: ov772x: use v4l2_ctrl to get current control value Akinobu Mita
2018-05-06 14:19 ` [PATCH v5 12/14] media: ov772x: avoid accessing registers under power saving mode Akinobu Mita
2018-05-14 9:06 ` jacopo mondi
2018-05-14 9:49 ` Sakari Ailus
2018-05-14 10:03 ` jacopo mondi
2018-05-06 14:19 ` [PATCH v5 13/14] media: ov772x: make set_fmt() and s_frame_interval() return -EBUSY while streaming Akinobu Mita
2018-05-14 9:10 ` jacopo mondi
2018-05-06 14:19 ` [PATCH v5 14/14] media: ov772x: create subdevice device node Akinobu Mita
2018-05-14 9:11 ` jacopo mondi
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