From: Stephen Warren <swarren@wwwdotorg.org>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH 2/2] WIP: tegra: i2c: Enable new CONFIG_SYS_I2C framework
Date: Tue, 13 Nov 2012 10:30:06 -0700 [thread overview]
Message-ID: <50A2839E.1030905@wwwdotorg.org> (raw)
In-Reply-To: <50A1E780.4090807@denx.de>
On 11/12/2012 11:24 PM, Heiko Schocher wrote:
> Hello Stephen,
>
> On 08.11.2012 18:05, Stephen Warren wrote:
>> On 11/07/2012 11:47 PM, Heiko Schocher wrote:
>>> On 01.11.2012 18:03, Stephen Warren wrote:
>> ...
>>>> I'd suggest having a CONFIG_SYS_I2C_DRIVERS variable at most, and each
>>>> driver registers an arbitrary number of adapters and/or buses during
>>>> its
>>>> initialization.
>>>
>>> Why should an i2c driver register buses? That is board specific.
>>
>> I don't entirely agree here. Certainly the information is
>> board-specific, but I don't believe that precludes bus registration
>> occurring from the I2C adapter drivers themselves, based on information
>> passed from a board file or device tree.
>>
>> If a particular adapter is instantiated by the board, then there is
>> clearly an I2C bus attached to that adapter. Hence, it's quite
>> reasonable for the adapter itself to register the bus directly attached
>> to it.
>
> But some i2c drivers have more than one instance... would you for all
> boards register all possible instances of a driver? ...
Register, but perhaps not initialize, seems fine to me.
After all, what if the user wishes to use the I2C adapters for some
custom command; up-front registration of all valid adapters is required
for that, although actual initialization can always be deferred until
if/when the adapter is actually used.
The other issue is that as I pointed out before, the move to define
which I2C (and all other peripheral) adapters are used via device tree
rather than board/config files on some U-Boot platforms seems completely
at odds with not always registering all I2C adapters, at least on the
platforms that use device tree.
>> Following on from there, if there's an I2C bus mux attached to some I2C
>> bus, then there are clearly I2C buses downstream from the bus mux, and
>> the bus mux driver knows exactly how many there are, and can register
>> those buses.
>
> Here again, why register all possible buses? We are just a bootloader ...
I don't see how being a bootloader is relevant. After all, people can
use for example U-Boot I2C or GPIO commands for board bringup, to
implement HW initialization via custom boot scripts, etc.
next prev parent reply other threads:[~2012-11-13 17:30 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-30 17:28 [U-Boot] [PATCH 1/2] tegra: i2c: Add function to know about current bus Simon Glass
2012-10-30 17:28 ` [U-Boot] [PATCH 2/2] WIP: tegra: i2c: Enable new CONFIG_SYS_I2C framework Simon Glass
2012-10-30 22:32 ` Stephen Warren
2012-10-31 6:00 ` Heiko Schocher
2012-10-31 15:41 ` Stephen Warren
2012-10-31 15:56 ` Simon Glass
2012-10-31 16:25 ` Stephen Warren
2012-11-01 7:42 ` Heiko Schocher
2012-11-01 17:03 ` Stephen Warren
2012-11-05 20:39 ` Simon Glass
2012-11-08 7:02 ` Heiko Schocher
2012-11-08 18:03 ` Simon Glass
2012-11-08 6:47 ` Heiko Schocher
2012-11-08 17:05 ` Stephen Warren
2012-11-13 6:24 ` Heiko Schocher
2012-11-13 7:48 ` Wolfgang Denk
2012-11-13 17:30 ` Stephen Warren [this message]
2012-10-31 5:53 ` Heiko Schocher
2012-10-31 5:26 ` [U-Boot] [PATCH 1/2] tegra: i2c: Add function to know about current bus Heiko Schocher
2012-11-05 20:43 ` Simon Glass
2012-11-08 7:05 ` Heiko Schocher
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