linux-kernel - Re: [RFC v2] [ALSA][CONTROL] 1. Added 2 ioctls for reading/writing values of multiple controls in one go (at once) 2. Restructured the code for read/write of a single control

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Date:   Tue, 07 Feb 2017 07:24:56 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Takashi Sakamoto <o-takashi@...amocchi.jp>
Cc:     Satendra Singh Thakur <satendra.t@...sung.com>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        hemanshu.s@...sung.com, nishant.s4@...sung.com
Subject: Re: [RFC v2] [ALSA][CONTROL] 1. Added 2 ioctls for reading/writing values of multiple controls in one go (at once) 2. Restructured the code for read/write of a single control

On Tue, 07 Feb 2017 05:33:05 +0100,
Takashi Sakamoto wrote:
> 
> On Feb 3 2017 16:24, Takashi Iwai wrote:
> > On Thu, 02 Feb 2017 04:45:48 +0100,
> > Takashi Sakamoto wrote:
> >>
> >> I'm _strongly_ interested in your two patches, because it has a
> >> potentiality to purge ASoC abuse of TLV feature, which was introduced
> >> in  2014 with a bad reviewing process.
> >
> > I don't think it can be a replacement for the extended TLV usages.
> > The proposed API is nothing but a loop of ctl elem read/write, and I'm
> > not sure whether it worth to introduce the new ioctls just for that.
> 
> In my opinion, an idea to handle several control elements in one system
> call could perhaps overcome current limitation of control elements,
> which comes from definition of 'struct snd_ctl_elem_value'. Aim of the
> abuse of TLV feature in ASoC part essentially comes from the
> limitation, as long as I understand.

Yes, it's the limitation, but it won't be eased by this kind of patch.
The TLV usage came just because of its required data size, sometimes
over mega bytes.  It's not about the number of elements.  It's about
the data size a single element needs to deal with.


Takashi