linux-kernel - Re: [RFC PATCH 0/3] Separate BE DAI HW constraints from FE ones

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Message-ID: <5e1fb981-48c1-7d5a-79a6-ba54bac26165@microchip.com>
Date:   Tue, 23 Mar 2021 14:18:28 +0000
From:   <Codrin.Ciubotariu@...rochip.com>
To:     <perex@...ex.cz>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>
CC:     <tiwai@...e.com>, <lgirdwood@...il.com>, <broonie@...nel.org>,
        <mirq-linux@...e.qmqm.pl>, <gustavoars@...nel.org>
Subject: Re: [RFC PATCH 0/3] Separate BE DAI HW constraints from FE ones

On 23.03.2021 14:15, Jaroslav Kysela wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Dne 23. 03. 21 v 12:43 Codrin Ciubotariu napsal(a):
> 
>> To achieve this, the first thing needed is to detect whether a HW
>> constraint rule is enforced by a FE or a BE DAI. This means that
>> snd_pcm_hw_rule_add() needs to be able to differentiate between the two
>> type of DAIs. For this, the runtime pointer to struct snd_pcm_runtime is
>> replaced with a pointer to struct snd_pcm_substream, to be able to reach
>> substream->pcm->internal to differentiate between FE and BE DAIs.
> 
> Think about other not-so-invasive solution. What about to use
> 'runtime->private_data' (struct snd_soc_pcm_runtime *) to determine FE / BE?
> 

I think struct snd_soc_pcm_runtime * is placed in 
substream->private_data, while runtime->private_data is used more by the 
platform drivers. runtime->trigger_master could be an idea, but it looks 
like it's initialized just before the trigger callback is called, way 
after the constraint rules are added and I am not sure it can be 
initialized earlier...

Best regards,
Codrin