From: Maxime Ripard <maxime.ripard@free-electrons.com>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: "Vinod Koul" <vinod.koul@intel.com>,
dmaengine@vger.kernel.org, lars@metafoo.de,
linux-kernel@vger.kernel.org,
"Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
linux-arm-kernel@lists.infradead.org,
"Antoine Ténart" <antoine@free-electrons.com>
Subject: Re: [PATCH 7/9] dmaengine: Move slave caps to dma_device
Date: Wed, 1 Oct 2014 10:27:05 +0200 [thread overview]
Message-ID: <20141001082705.GF6884@lukather> (raw)
In-Reply-To: <20140927092846.GA5182@n2100.arm.linux.org.uk>
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On Sat, Sep 27, 2014 at 10:28:47AM +0100, Russell King - ARM Linux wrote:
> On Sat, Sep 27, 2014 at 10:54:43AM +0200, Maxime Ripard wrote:
> > The previous code was relying on the fact that the slave_caps were to be
> > defined on a per channel basis.
> >
> > However, this proved to be a bit overkill, since every driver filling these so
> > far were hardcoding it, disregarding which channel was actually given.
> >
> > Add these capabilities to the dma_device structure, so that drivers can just
> > provide them at probe time, and be done with it.
>
> This is also buggy for the same reason as patch 6.
Indeed
> The only way to do this is to either have a flag day, fixing all drivers
> at once (which isn't going to happen) or leave the caps code as-is, and
> provide a library function which drivers can hook into the caps callback
> which retrieves the information from dma_device.
>
> That way, DMA engine drivers which are using the new method can just
> install the new function, and those which haven't been updated with
> capabilities can carry on as they are, and are detectable to drivers.
Which is pretty much the current behaviour, isn't it?
> What would be acceptable is to have the DMA engine registration function
> spot the lack of DMA caps function and print a warning at boot to
> encourage people to add it.
That would be an option too.
Maxime
--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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next prev parent reply other threads:[~2014-10-01 8:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-27 8:54 [PATCH 0/9] dmaengine: Implement generic slave capabilities retrieval Maxime Ripard
2014-09-27 8:54 ` [PATCH 1/9] dmaengine: Make the destination abbreviation coherent Maxime Ripard
2014-09-27 8:54 ` [PATCH 2/9] dmaengine: Make channel allocation callbacks optional Maxime Ripard
2014-09-28 16:07 ` Vinod Koul
2014-10-01 8:39 ` Maxime Ripard
2014-09-27 8:54 ` [PATCH 3/9] dmaengine: Introduce a device_config callback Maxime Ripard
2014-09-28 16:13 ` Vinod Koul
2014-09-28 16:14 ` Vinod Koul
2014-09-27 8:54 ` [PATCH 4/9] dmaengine: split out pause/resume operations from device_control Maxime Ripard
2014-09-27 8:54 ` [PATCH 5/9] dmaengine: Add device_terminate_all callback Maxime Ripard
2014-09-27 8:54 ` [PATCH 6/9] dmaengine: Create a generic dma_slave_caps callback Maxime Ripard
2014-09-27 9:25 ` Russell King - ARM Linux
2014-10-01 8:21 ` Maxime Ripard
2014-09-27 8:54 ` [PATCH 7/9] dmaengine: Move slave caps to dma_device Maxime Ripard
2014-09-27 9:28 ` Russell King - ARM Linux
2014-10-01 8:27 ` Maxime Ripard [this message]
2014-10-01 8:55 ` Russell King - ARM Linux
2014-09-27 8:54 ` [PATCH 8/9] dmaengine: Mark device_control as deprecated Maxime Ripard
2014-09-27 8:54 ` [PATCH 9/9] dmaengine: sun6i: Convert to generic slave_caps Maxime Ripard
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