linux-kernel - Re: [PATCH v7 05/11] dmaengine: Introduce DMA-device device

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Message-ID: <f746fafd-851e-f402-3755-03ef94a65988@intel.com>
Date:   Tue, 14 Jul 2020 09:18:16 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh+dt@...nel.org>, linux-mips@...r.kernel.org,
        devicetree@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 05/11] dmaengine: Introduce DMA-device device_caps
 callback



On 7/14/2020 9:08 AM, Vinod Koul wrote:
> On 13-07-20, 13:55, Dave Jiang wrote:
>>
>>
>> On 7/10/2020 2:38 AM, Serge Semin wrote:
>>> On Fri, Jul 10, 2020 at 11:45:03AM +0300, Andy Shevchenko wrote:
>>>> On Fri, Jul 10, 2020 at 01:45:44AM +0300, Serge Semin wrote:
>>>>> There are DMA devices (like ours version of Synopsys DW DMAC) which have
>>>>> DMA capabilities non-uniformly redistributed between the device channels.
>>>>> In order to provide a way of exposing the channel-specific parameters to
>>>>> the DMA engine consumers, we introduce a new DMA-device callback. In case
>>>>> if provided it gets called from the dma_get_slave_caps() method and is
>>>>> able to override the generic DMA-device capabilities.
>>>>
>>>
>>>> In light of recent developments consider not to add 'slave' and a such words to the kernel.
>>>
>>> As long as the 'slave' word is used in the name of the dma_slave_caps
>>> structure and in the rest of the DMA-engine subsystem, it will be ambiguous
>>> to use some else terminology. If renaming needs to be done, then it should be
>>> done synchronously for the whole subsystem.
>>
>> What about just calling it dma_device_caps? Consider this is a useful
>> function not only slave DMA will utilize this. I can see this being useful
>> for some of my future code with idxd driver.
> 
> Some of the caps may make sense to generic dmaengine but few of them do
> not :) While at it, am planning to make it dmaengine_periph_caps to
> denote that these are dmaengine peripheral capabilities.
> 

If the function only passes in periph_caps, how do we allow the non periph DMA 
utilize this function?