linux-kernel - Generic VME UIO driver

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Message-Id: <6296E8BD-06B6-4FC2-859A-98B2E2ED66BF@gmail.com>
Date:	Wed, 8 Jul 2015 18:02:35 +0300
From:	Dmitry Kalinkin <dmitry.kalinkin@...il.com>
To:	Martyn Welch <martyn.welch@...com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
	Manohar Vanga <manohar.vanga@...il.com>,
	Igor Alekseev <igor.alekseev@...p.ru>
Subject: Generic VME UIO driver


> On 08 Jul 2015, at 16:22, Martyn Welch <martyn.welch@...com> wrote:
> 
> On 06/07/15 18:24, Dmitry Kalinkin wrote:
>>> Some functionality was dropped as it was not good practice
>>> >(such as receiving VME interrupts in user space, it's not really doable if
>>> >the slave card is Release On Register Access rather than Release on
>>> >Acknowledge),
>> Didn't know about RORA. I wonder how different this is compared to the
>> PCI bus case.
> 
> Little I suspect. What it does mean is that there's no generic mechanism for clearing down an interrupt, so a device specific interrupt routine is required, which needs to be in kernel space.
Yet PCI somehow managed to settle with UIO.
Now imagine I am working with a board using vme_user API and I need to
implement interrupts. The PCI case teaches me that I need to write a board specific
UIO driver. My board is ROAK and allows to configure it's interrupt to any level and
any status/id. So I only use a standard vme_irq_request API that generates IACK
cycle for me automatically. I also don’t want to limit my end user with a choice of
interrupt level and status/id and so I make it configurable. In the end I’ve got a very
generic ROAK device driver. What did I do wrong?

Cheers,
Dmitry--
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