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SubjectRE: [PATCH v2 2/2] drivers: remove force dma flag from buses

> -----Original Message-----
> From: Greg KH []
> Sent: Wednesday, March 21, 2018 15:05
> To: Nipun Gupta <>
> Cc:;;;
>;; iommu@lists.linux-
>;; linux-arm-
>;; Bharat Bhushan
> <>; Leo Li <>
> Subject: Re: [PATCH v2 2/2] drivers: remove force dma flag from buses
> On Wed, Mar 21, 2018 at 12:25:23PM +0530, Nipun Gupta wrote:
> > With each bus implementing its own DMA configuration callback,
> > there is no need for bus to explicitly have force_dma in its
> > global structure. This patch modifies of_dma_configure API to
> > accept an input parameter which specifies if implicit DMA
> > configuration is required even when it is not described by the
> > firmware.
> Having to "remember" what that bool variable means on the end of the
> function call is a royal pain over time, right?
> Why not just create a new function:
> dma_common_configure_force(dma)
> that always does this? Leave "dma_common_configure()" alone, and then
> wrap the old code with these two helper functions that call the 'core'
> code with the bool set properly?
> That way you do not have to "know" what that parameter is, the function
> name just documents it automatically, so when you see it in the
> bus-specific code, no need to go and have to hunt for anything. And if
> you are reading the dma core code, it's obvious what is happening as the
> functions are all right there.

How about we do not pass any flag in 'dma_common_configure()', and inside this
API we pass "true" to 'of_dma_configure()'? I am saying this because currently
both the busses (platform and AMBA) which uses 'dma_common_configure()' passes
"true" value. If we create additional 'dma_common_configure_force()', then
'dma_common_configure()' will not be used anytime and will become redundant.

If someday new busses come and they needs to use similar functionality which
'dma_common_configure()' provides, but with passing "false" to 'of_dma_configure()',
then what you suggests of having two separate such API's will be more reasonable
and can be implemented?


> thanks,
> greg k-h

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