linux-kernel - Re: [PATCH RFC] c_can_pci: generic module for c

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Message-ID: <4FCE07EE.40003@pengutronix.de>
Date:	Tue, 05 Jun 2012 15:21:50 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Alessandro Rubini <rubini@...dd.com>
CC:	bhupesh.sharma@...com, federico.vaga@...il.com,
	alan@...rguk.ukuu.org.uk, wg@...ndegger.com,
	giancarlo.asnaghi@...com, alan@...ux.intel.com,
	linux-can@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] c_can_pci: generic module for c_can on PCI

On 06/05/2012 03:13 PM, Alessandro Rubini wrote:
>>> My implementation is align to 32, but I'm trying to make a generic PCI
>>> wrapper (some other could be aligned to 16)
>  
>> So it means your implementation is also flaky and you are probably
>> wasting HW memory space while integrating the Bosch C_CAN module in
>> your SoC :)
> 
> Then I may say _your_ implementation is flaky because it wastes one
> bit in the address decoder and a lot of logic gates in the data
> bus. It's normal to align registers at 32 bits, as it's simpler and
> faster.  Most SoCs have only 32-bit aligned registers, for a reason.
> 
>> I am not a big fan of adding platform specific flakes in any core
>> file, that why we keep the platform file separate from the core
>> ones.
> 
> A number of other drivers have a shift parameter, because it's very
> common for the hardware integrator to feel free to choose the easiest
> wiring for the device.  The choice to keep the platform driver
> separate from the core driver only adds complication in my opinion:
> you need to export 4 symbols and yhen every user must duplicate code
> (like federico is replicating theplatform driver in the pci driver).
> 
> I'd really prefer to have the core driver be a platform driver, and
> the others just add platform data to describe how it is wired. That's
> actually the reason why the platform bus exists.
> 
>> But I will left Marc and Wolfgang to further comment on the same.
> 
> I agree: let them decide.

I personally like the "pci device sets up a platform device" idea.

My question is, is this considered being a good practise?

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
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