All of lore.kernel.org
 help / color / mirror / Atom feed
From: Wolfram Sang <wsa@the-dreams.de>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>,
	linux-media@vger.kernel.org,
	"open list:OPEN FIRMWARE AND..." <devicetree@vger.kernel.org>,
	Jacopo Mondi <jacopo+renesas@jmondi.org>,
	Hans Verkuil <hans.verkuil@cisco.com>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Mauro Carvalho Chehab <mchehab@s-opensource.com>
Subject: Re: [PATCH v3 02/11] media: ov772x: allow i2c controllers without I2C_FUNC_PROTOCOL_MANGLING
Date: Mon, 23 Apr 2018 22:11:21 +0200	[thread overview]
Message-ID: <20180423201121.cgcg6isobtku7swy@ninjato> (raw)
In-Reply-To: <3172940.h9isB0x1K9@avalon>

[-- Attachment #1: Type: text/plain, Size: 1482 bytes --]


> How about i2c_smbus_xfer_emulated() ? The tricky part will be to handle the 
> I2C adapters that implement .smbus_xfer(), as those won't go through 
> i2c_smbus_xfer_emulated(). i2c_smbus_xfer_emulated() relies on i2c_transfer(), 
> which itself relies on the I2C adapter's .master_xfer() operation. We're thus 
> only concerned about the drivers that implement both .smbus_xfer() and 
> master_xfer(), and there's only 4 of them (i2c-opal, i2c-pasemi, i2c-powermac 
> and i2c-zx2967). Maybe the simplest solution would be to force the emulation 
> path if I2C_CLIENT_SCCB && !I2C_FUNC_PROTOCOL_MANGLING && ->master_xfer != 
> NULL ?
> 
> Wolfram, what do you think ?

I think it is a mess :)

Further: I don't think we will ever see an SMBus controller which allows
mangling. SMBus is way more precisely defined than I2C, so HW can then
do much more things automatically. They will always do a REP_START, so I
don't think you can connect SCCB devices to SMBus.

As a result, we shouldn't do SMBus calls for SCCB. Maybe we should
introduce sccb_byte_read? SCCB didn't specify much more than byte read
IIRC, or? The implementation here with two seperate messages makes much
sense to me then.

I could argue that the sccb_* helpers should live in drivers/media since
it is probably only Omnivision trying to work around I2C licensing here?

But if it is not too heavy, maybe we could take it into i2c as well.

Makes sense or did I miss something?


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

  reply	other threads:[~2018-04-23 20:11 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-22 15:56 [PATCH v3 00/11] media: ov772x: support media controller, device tree probing, etc Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 01/11] media: dt-bindings: ov772x: add device tree binding Akinobu Mita
2018-04-23  9:17   ` Laurent Pinchart
2018-04-23 15:54     ` Akinobu Mita
2018-04-25 16:19       ` Akinobu Mita
2018-04-25 22:40         ` Laurent Pinchart
2018-04-26 16:17           ` Akinobu Mita
2018-04-26 18:11             ` jacopo mondi
2018-04-26 21:34             ` Laurent Pinchart
2018-04-27 17:15               ` Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 02/11] media: ov772x: allow i2c controllers without I2C_FUNC_PROTOCOL_MANGLING Akinobu Mita
2018-04-23  9:18   ` Laurent Pinchart
2018-04-23 15:55     ` Akinobu Mita
2018-04-23 19:41       ` Laurent Pinchart
2018-04-23 20:11         ` Wolfram Sang [this message]
2018-04-23 20:21           ` Laurent Pinchart
2018-04-23 20:36             ` Wolfram Sang
2018-04-23 20:51               ` Laurent Pinchart
2018-04-24 10:04                 ` Sakari Ailus
2018-04-26 12:32                 ` Wolfram Sang
2018-04-22 15:56 ` [PATCH v3 03/11] media: ov772x: add checks for register read errors Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 04/11] media: ov772x: add media controller support Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 05/11] media: ov772x: use generic names for reset and powerdown gpios Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 06/11] media: ov772x: support device tree probing Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 07/11] media: ov772x: handle nested s_power() calls Akinobu Mita
2018-04-23  8:35   ` jacopo mondi
2018-04-27 17:20     ` Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 08/11] media: ov772x: reconstruct s_frame_interval() Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 09/11] media: ov772x: avoid accessing registers under power saving mode Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 10/11] media: ov772x: make set_fmt() return -EBUSY while streaming Akinobu Mita
2018-04-22 15:56 ` [PATCH v3 11/11] media: ov772x: create subdevice device node Akinobu Mita

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180423201121.cgcg6isobtku7swy@ninjato \
    --to=wsa@the-dreams.de \
    --cc=akinobu.mita@gmail.com \
    --cc=devicetree@vger.kernel.org \
    --cc=hans.verkuil@cisco.com \
    --cc=jacopo+renesas@jmondi.org \
    --cc=laurent.pinchart@ideasonboard.com \
    --cc=linux-media@vger.kernel.org \
    --cc=mchehab@s-opensource.com \
    --cc=sakari.ailus@linux.intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.