From: wmb@firmworks•com (Mitch Bradley)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] ARM: vexpress: initial device tree support
Date: Wed, 11 Jan 2012 13:20:03 -1000 [thread overview]
Message-ID: <4F0E1923.4090703@firmworks.com> (raw)
In-Reply-To: <4F0DEE4F.3080103@freescale.com>
On 1/11/2012 10:17 AM, Timur Tabi wrote:
> 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.
You make device nodes for each of the i2c adapters (possibly with a GPIO
I2C mux node underneath the EDID one), then you point to the correct
adapter (or mux) node with a phandle-valued property in the video node.
Of course, you need the deferral patch cited in another message.
>
>>> 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.
>
>
next prev parent reply other threads:[~2012-01-11 23:20 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
2012-01-11 23:20 ` Mitch Bradley [this message]
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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