linux-kernel - Driver Design Question

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Message-ID: <20131022070256.GA5527@jtlinux>
Date:	Tue, 22 Oct 2013 09:02:56 +0200
From:	Johannes Thumshirn <johannes.thumshirn@....de>
To:	<linux-kernel@...r.kernel.org>
CC:	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>, Michael Buesch <m@...s.ch>,
	Johannes Thumshirn <johannes.thumshirn@....de>
Subject: Driver Design Question

Hi List,

I have a design question concerning a device driver. The device in question is
somewhere in between drivers/mfd/timberdale and drivers/ssb. It is mapped
connected via PCI and on PCI Bar 0 there is a table describing which
"sub-devices" are contained in the FPGA as well as where their Memory and IRQ
resources are.

Unlike the timberdale driver, there is no static configuration of the FPGA's
sub-devices, but their number and kind is variable. But luckily we have unique
device-ids for every sub-device, so it is possible to do a PCI/USB like
enumeration.

In my understanding the MFD API, which timberdale uses, isn't tailored to this
Plug'n'Play like behavior. Whereas the I think (virtual) bus concept used by
SSB is much more suited for this kind of devices. But would it be wise to add a
bus only suited to devices manufactured by one vendor, when there is already a
API for such kinds of multi function devices?

Long story short, which would be the preferred way to implement such a driver? At
the point I currently reached I could go in both directions.

I'd appreciate any advice I can get on this topic.

Thanks in advance,

       Johannes

P.S.: MFD and SSB maintainers are on CC as I'd really like to hear their opinion
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