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From: timur@freescale•com (Timur Tabi)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] ARM: vexpress: initial device tree support
Date: Wed, 11 Jan 2012 14:17:19 -0600	[thread overview]
Message-ID: <4F0DEE4F.3080103@freescale.com> (raw)
In-Reply-To: <4F0D2F90.8020801@firmworks.com>

Mitch Bradley wrote:

> I think that would not be a good design.  Presence and location of EDID 
> data is not something that a generic I2C driver should know.  It's the 
> video controller that knows that EDID exists, where it is located 
> (device ID 0x50 and addresses within that device), and what it means.

But the video driver does not know what I2C *bus* it's on.  I have been unable to come up with a way to obtain the proper i2c_adapter object to use when looking for EDID data.  

>>  That won't work if I have multiple video controllers, since I won't know which EDID data goes with which video controller.  I tried adding a call to i2c_add_driver() in my framebuffer driver, but the I2C probe function was called *after* the framebuffer's probe function, so that doesn't help me.
> 
> Then there needs to be some sort of ordering or dependency to ensure 
> that the I2C driver is activated before the framebuffer driver tries to 
> use it.

I don't know how to do that, either.

> Either way, you need platform-dependent functions to do the switching, 
> and you need to select the appropriate channel.  Personally, I don't see 
> the advantage of using the mux device in this case.  It's just adding 
> complexity with no payback.

I'm always in favor of doing things the simpler way.


-- 
Timur Tabi
Linux kernel developer at Freescale

  reply	other threads:[~2012-01-11 20:17 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-21  9:19 [PATCH] ARM: vexpress: initial device tree support Dave Martin
2011-09-21 13:24 ` Rob Herring
2011-09-21 14:24   ` Dave Martin
2011-09-21 14:33     ` Pawel Moll
2011-09-21 15:49       ` Dave Martin
2011-09-21 14:57   ` Grant Likely
2011-09-21 16:01     ` Pawel Moll
2011-09-21 16:17       ` Dave Martin
2011-09-21 16:28         ` Pawel Moll
2011-09-21 16:37     ` Rob Herring
2011-09-21 17:15       ` Dave Martin
2011-09-21 17:47         ` Mitch Bradley
2011-09-22 12:19           ` Dave Martin
2012-01-09 23:26 ` Tabi Timur-B04825
2012-01-10  0:42   ` Mitch Bradley
2012-01-10  2:24     ` Tabi Timur-B04825
2012-01-10 12:22     ` Jamie Lokier
2012-01-10 21:58       ` Timur Tabi
2012-01-10 22:35         ` Mitch Bradley
2012-01-10 23:55           ` Stephen Warren
2012-01-11  0:02             ` Timur Tabi
2012-01-11  0:28           ` Timur Tabi
2012-01-11  6:43             ` Mitch Bradley
2012-01-11 20:17               ` Timur Tabi [this message]
2012-01-11 23:20                 ` Mitch Bradley
2012-01-11 23:32                   ` Timur Tabi
2012-01-11 20:29               ` Stephen Warren
2012-01-11 20:32                 ` Timur Tabi
2012-01-11 20:36                   ` Stephen Warren
2012-01-11 21:37                     ` Timur Tabi
2012-01-11 21:57                       ` Stephen Warren
2012-01-12 12:24                     ` Jamie Lokier
2012-01-12 16:49                       ` Stephen Warren
2012-01-11 23:16                 ` Mitch Bradley
2012-01-12  0:15                   ` Stephen Warren
2012-01-12  0:38                     ` Mitch Bradley
2012-01-12  0:47                       ` Mitch Bradley
2012-01-12 16:45                       ` Stephen Warren
2012-01-12 12:09                     ` Jamie Lokier
2012-01-12 16:52                       ` Stephen Warren
2012-01-10 11:04   ` Dave Martin

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