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Subject: Re: [PATCHv3 08/16] staging: vme_user: provide DMA functionality
From: Dmitry Kalinkin <dmitry.kalinkin@gmail.com>
In-Reply-To: <CAPk1OjHQDfrDsZKYfbHoRot6RsqGS6HHytLvAwjKTjraNmSpkQ@mail.gmail.com>
Date: Tue, 7 Jul 2015 16:04:18 +0300
Cc: Martyn Welch <martyn.welch@ge.com>, devel@driverdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Igor Alekseev <igor.alekseev@itep.ru>,
        LKML <linux-kernel@vger.kernel.org>,
        Manohar Vanga <manohar.vanga@gmail.com>
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To: Alessio Igor Bogani <alessioigorbogani@gmail.com>
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> On 07 Jul 2015, at 15:51, Alessio Igor Bogani <alessioigorbogani@gmail.com> wrote:
> 
<snip>
>> Current VME stack links windows not to the boards, but to device drivers.
>> Driver
>> could potentially minimise window usage within it’s scope (any sort of
>> window
>> reusing, like mapping whole A16 once to be used with all boards), but this
>> won’t
>> work across multiple drivers. Even if all of your drivers are window-wise
>> economic,
>> they will still need some amount of windows per each driver. Not that we
>> have that
>> many kernel drivers...
> 
> Yes you can share a window/image between all boards of the same type
> (in effect we are porting our drivers in this way) *but* it isn't the
> expected way to work (see Documentation/vme_api.txt struct
> vme_driver's probe() and match() functions and the GE PIO2 VME
> driver).
And vme_pio2 can’t handle more than 8 boards. This shows that the current
design needs some adjustments. Also would be great if probe() and match()
allowed for void *private data field.

Cheers,
Dmitry--
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