linux-kernel - Re: [PATCH 01/11] ASoC: dai_dma: remove slave

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Date:   Mon, 15 Nov 2021 17:46:22 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Lars-Peter Clausen <lars@...afoo.de>,
        Arnd Bergmann <arnd@...nel.org>
Cc:     Vinod Koul <vkoul@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Andy Gross <agross@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Baolin Wang <baolin.wang7@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hyun Kwon <hyun.kwon@...inx.com>,
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Subject: Re: [PATCH 01/11] ASoC: dai_dma: remove slave_id field

15.11.2021 14:53, Lars-Peter Clausen пишет:
> On 11/15/21 11:42 AM, Arnd Bergmann wrote:
>> On Mon, Nov 15, 2021 at 11:14 AM Lars-Peter Clausen <lars@...afoo.de>
>> wrote:
>>> On 11/15/21 9:53 AM, Arnd Bergmann wrote:
>>>> From: Arnd Bergmann <arnd@...db.de>
>>>>
>>>> This field is never set, and serves no purpose, so remove it.
>>> I agree that we should remove it. Its been legacy support code for a
>>> while, but the description that there is no user is not right.
>>>
>>> The tegra20_spdif driver obviously uses it and that user is removed in
>>> this patch. I think it makes sense to split that out into a separate
>>> patch with a description why the driver will still work even with
>>> slave_id removed. Maybe the best is to remove the whole tegra20_spdif
>>> driver.
>> Ok, I'll split out the tegra patch and try to come up with a better
>> description for it. What I saw in that driver is it just passes down the
>> slave_id number from a 'struct resource', but there is nothing in
>> the kernel that sets up this resource.
>>
>> Do you or someone else have more information on the state of this
>> driver? I can see that it does not contain any of_device_id based
>> probing, so it seems that this is either dead code, the platform_device
>> gets created by some other code that is no longer compatible with
>> this driver.
> 
> I've looked into this a while back, when I tried to remove slave_id. And
> as far as I can tell there were never any in-tree users of this driver,
> even back when we used platform board files. Maybe somebody from Nvidia
> knows if there are out-of-tree users.

That Tegra SPDIF driver was never used. Still there is a growing
interest nowadays in making it alive by implementing HDMI audio support
for Tegra20 SoC. It was on my todo list for a long time, I'll try to
prioritize that work 5.17, it shouldn't take much effort.

The slave_id should be removed anyways, it won't be needed.